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The what if A65 67hp challenge. #782021 08/20/19 9:07 am
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Mark Parker Offline OP
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67hp is what Honda claimed for their newly introduced CB750 OHC 4. It's quite possible at some stage Honda actually achieved that power on their dyno. Rear wheel dyno graphs of CB750s sold to the public proved to be shy of that output even when converting for the losses through the drive train. One CB750 tested in the US delivered 54rwhp @ 8,000rpm indicating around 61.5hp at the crankshaft.

What interests me is the fact that the BSA factory chose not to machine A65 inlet ports to the actual design drawing, ever, and when Umbeslade Hall technicians actually machined the inlet ports to the design drawings their motor made 8hp more on their dyno than production line units. This was an oil in frame photo shoot Firebird built in 1970. Not only was the engine more powerful it was also more responsive. The only difference was the machining of the cylinder head.

I'm curious what the result would be to machining the A65 inlet ports to one of the most efficient two valve port shapes known today. To do this I've enlarged the port slightly to 32mm and used a 42mm inlet valve from MAP Cycles. I'll also use slightly O/Size exhaust valves as well, though its probably unnecessary. So the head is ported and on my somewhat home made flow bench is indicating an excellent gain in flow 160cfm @ 28"W @.385"of lift compared to the factory heads 109cfm.

Fitting a round-slide carb restricts flow especially at 30-32mm bore. A 32mm Mikuni with long bellmouth reduced flow to 135.2cfm, with the bellmouth removed it was better at 139.17cfm, blending the carb intake enabled 145.5cfm.

Using Wallace Racing's on line hp calculator which bases its figures on intake port flow a 40cubic inch twin flowing 109cfm can produce 52hp at the crank (similar to BSAs claimed output) or 45.7rwhp approx. though like the XS650 Yamaha stock A65s are usually around 43-44rwhp. Calculating for 145cfm gives a estimate of 69hp at the crank, if it could achieve that it would translate to about 60.72rwhp.

So I'm interested to see if an otherwise stock A65 fitted with this head and 32mm carbs could equal or better the CB750s hp claim.

The modified carb:

[Linked Image from i.postimg.cc]

The new port shape:

[Linked Image from i.postimg.cc]

Not the actual head but one just like it.

[Linked Image from i.postimg.cc]

[Linked Image from i.postimg.cc]


mark
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Re: The what if A65 67hp challenge. [Re: Mark Parker] #782029 08/20/19 12:08 pm
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is this a round port Mark or have you filled the port floor?


beerchug
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782030 08/20/19 12:16 pm
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Oval port with filled floor.


mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782104 08/21/19 4:16 am
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And if BSA had actually done this to every production model they would have had to charge how much for each bike? They had enough trouble selling them at the price they charged.
Looks like a fun project though.


Stepping on others doesn't make you stand tall.

71 A65L "Zelda"
92 BMW K100rs "Gustav"
72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782120 08/21/19 10:57 am
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I'm really interested in hearing how it develops. I've been stopped by back and shoulder issues getting out into the shed and need some motivation. Mark has posted so much interesting information here and love his builds


Current: 2 x 1966 A65S, 1 x 1967 A65SA, 1 x 69/70? A65LA space Y, 1 X D14/4 & 1 x B175
Past: 4 x 1976 T160V, 1 74/5 T150V, 83 model GSX 750 ESD, Z650, Katana 1100(Bathurst Model), 79 T140V, 70's TR6, 2 x 1971 BSA 250 Gold Stars, 50's 350 Goldie, A65 Spitfire semi basket case, 1965/6? A65 LC, Tiger 21 350 & a D14/4 Bantam, 175 Bridgestone Twin with Zimmerman discs!
Re: The what if A65 67hp challenge. [Re: DavidP] #782125 08/21/19 11:57 am
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Originally Posted by DavidP
And if BSA had actually done this to every production model they would have had to charge how much for each bike? They had enough trouble selling them at the price they charged.
Looks like a fun project though.


Costs just as much to make something properly as it does it make something incorrect.

Be interested to know what the difference in the blueprint head and the other heads. theres 2 casting/part numbers for the OIF 2 carbs heads, a few suttle differences between them, but never measured the ports..... too late now as both of them are modified.


beerchug
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782134 08/21/19 1:21 pm
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Mark Parker Offline OP
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It's not particularly hard to do the ports by hand. BSA could have done the ports at least to how they were designed rather than short cutting at the factory, it may have been saving them a little money and keep the A65 on parity with the Triumph twin which they also owned. In 1970 they knew the difference between the heads but didn't rectify the production, they could have had 8 more hp in 1971. In their day these bikes were among the fastest most powerful on the road, but they were about to be displaced, or by 1971 they were being displaced by the 750s and the power bikes from Japan.

It was hardly a time to throw away easy hp in what was a full-scale hp race. You can see this when the mighty Z1 Kawasaki turned up, it was called the King. It was developed as a 750 but Honda released the CB750 4, getting the jump. Kawasaki held off releasing their bike till they increased the displacement to 903cc the reason they did that was to sell bikes, they understood the power of power. Honda claimed 67hp Kawasaki trounced it with 82hp and 54.2ftlb, though it was heavy at 542lb. For perspective my 883cc A65 weighs around 360lb and produces 97hp and 71ftlb it also has a very wide power spread. It uses a bigger version of the oval port above, so I'm interested to see how that translates onto an otherwise stock engine.

BSA already knew how to fix all the problems with the A65, roller mains both sides would have reversed market resistance, 71 or earlier they had excellent steel capped rods, high volume oil pumps and they had the A70 showing great potential. But they sank money and effort into things like the Ariel 3. And also the 350s that were a good idea though eventually scrapped because of a shot to the foot.

The 350 was a missed opportunity, they could not get good power from it because the head design was poor, DH had made an error, easy to rectify with a new casting, but management told him no. So 34hp was the best they could ever get. The 350 Honda was already in the market with similar power, the BSA 350 could and should have made 45+hp, and it would have been a winner, it could then be more expensive than the Honda because it gave more, it had the advantage with a state of the art frame and running gear already. A company like Kawasaki would have made sure they had what they needed to get the power necessary. So rather than spend massive effort and money fruitlessly down these paths, BSA could have done three things, fixed the A65 engine completely, and at the same time, because its basically the same thing, developed the A70And the third, built at least a limited number of Rob North style Rocket threes, the frames were state of the art and exotic, cheaper to manufacture than the std frames. The threes also work extremely well at 850cc if they wanted to respond to the Z1 and Ducati's SS750 when they came along.


mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782136 08/21/19 1:24 pm
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Hey Allan, they changed the angle of the exhaust ports in 71 from what I've read. The '71 inlet ports are a bit different, but they are not good.


mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782143 08/21/19 3:20 pm
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Hopwood in his book states the attitude of the Managing Director that BSA and Triumph machinery must be equally prepared so it was unlikely they would have made the improvement to the A65. When Dan Macias visited the Triumph factory he saw they were finishing the Triumph twin ports on a drill press. Doug Hele told him not to mention it because the operator had been doing it that way for many years.
By May 1971 BSA was looking at a loss of 1m GBP so was hardly in the position to make any changes to the design.
I think the A70 was the only one with steel capped rods but not sure.
The 350 was a disaster because it was "designed" by Turner (who checked valve springs by stepping on them with his heel). Two broken crankshafts and one valve gear failure in 1500 miles. The cutaway picture of the engine shows the characteristic Turner sharp angle between the port and valve. Also, by '71 you think they would have figured out it was a bad idea to put the output sprocket between the clutch and gearbox.

Re: The what if A65 67hp challenge. [Re: Mark Parker] #782151 08/21/19 4:18 pm
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I hear you Mark, there was little stopping them making a full production model of the A70, I think they made more Lightnings than Thunderbolts from 71 (sure seems that way as theyres loads of Lightnings and L stamped cases around compared to the T's) 850cc would have been a good step forward on the Mk2 Rocket 3..... Still such as life.


beerchug
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782180 08/21/19 10:38 pm
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A massive slice of their market was the 'states.
It would have been more of a benefit to make the a65 more reliable and long lived than to uprate it's horsepower.
The average bloke who bought a bike wasn'r racing it, he was riding it once a week and poorly maintaining it.
His mates with triumphs could get away with not changing oil etc so he would do the same...........the beezer went bang.
They should have shut down in 1963 and moved production to the far east, that way they would have had local access to
a massive market and government funded factories/development. Competing with japan's zero interest rate for business at
that time was impossible, they could product dump anywhere in the western world with government backing, and they did.
Beezer was nothing compared to the yankee electronics industry they devastated.
The management at beezer were just selling it all off and getting out, they didn't want to make motorbikes, they wanted to
make money. Pi$$ing about modifying cylinder heads on an out of date engine that's been in production for 10+ years
is the sort of thing that makes firms go broke.
I understand the nostalgia and i love the old crates as well, but politics and economics etc. get in the way.

Re: The what if A65 67hp challenge. [Re: Mark Parker] #782184 08/21/19 11:54 pm
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How long will a 67 HP 650 BSA engine last at high out put levels? .......Mark's project is interesting...let's see how it goes..... My 650 Triumph land speed racer is the only comphrensive dyno info I've seen on a Brit 650...It's like a T120 engine with a bit more cam and compression , 34mm carbs and raised intake port head. On a Superflow dyno, not the more optimistic Dynojet, it made 55 rwhp @ 7100 rpm and 46 ft lbs torque @5100 rpm. later on I moved the cam timing and the bike went a few MPH faster so maybe 58 rwhp at best...So maybe 65 hp at the crank?
Can a BSA make more power than one of Turner's turds? grin


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782192 08/22/19 1:53 am
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I have a half done '70 firebird in the shed with roller conversion bottom end, I'm just curious. If it got anything around 50 or more at the wheel it would be pretty cool, but you don't know what is actually possible without trying. Don't like the idea of the 360degree crank and the vibes but it would be interesting and give me motivation to build the Firebird.


mark
Re: The what if A65 67hp challenge. [Re: Allan Gill] #782201 08/22/19 4:23 am
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Originally Posted by Allan Gill

Costs just as much to make something properly as it does it make something incorrect.

Then why didn't BSA do it properly?
It always seemed to me that the A65 was like the Combat Norton,a desperate attempt to wring modern performance from an antique design. At least Norton improved the bearings after that fiasco. BSA didn't even bother to update their oil system.


Stepping on others doesn't make you stand tall.

71 A65L "Zelda"
92 BMW K100rs "Gustav"
72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
Re: The what if A65 67hp challenge. [Re: DavidP] #782202 08/22/19 4:58 am
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Originally Posted by DavidP
Originally Posted by Allan Gill

Costs just as much to make something properly as it does it make something incorrect.

Then why didn't BSA do it properly?
It always seemed to me that the A65 was like the Combat Norton,a desperate attempt to wring modern performance from an antique design. At least Norton improved the bearings after that fiasco. BSA didn't even bother to update their oil system.


Machining heads at that time cost plenty on a production line.

Antique designs, well the turner design trumpets carried on until the 80's with few changes.
The a65 was a 'new' design in 1962 when launched, all triumph did was made theirs unit construction.
Norton tried using cheap bearings as a cost saver and that failed, beezer never did that. So many would have been saved if
they had just fitted an oil filter. The a65 motor is a sound old thing really, and oil tight if put together properly.
The old saga of the TS bush keeps coming up but there's nothing wrong with it when used with clean oil.
That's what cars are using. Many a10's did huge mileage as did early triumphs with a bush main.
It needed a non-return valve setup that lasted too.
Having used one in a sidecar outfit i've a lot of respect for the abuse the motor will stand when absolutely thrashed.
(even 2 years with a standard TS bush! as a 650 and 750!)
Shouldn't triumph have tried to cure the oil leak problems they had? or the timing gear rattles? It took 'em long enough
to get the bloody things to handle eh?
You could say similar stuff about all of 'em really, they were good enough in their day and that was a long time ago.

Re: The what if A65 67hp challenge. [Re: DMadigan] #782203 08/22/19 5:10 am
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Originally Posted by DMadigan
Hopwood in his book states the attitude of the Managing Director that BSA and Triumph machinery must be equally prepared so it was unlikely they would have made the improvement to the A65. When Dan Macias visited the Triumph factory he saw they were finishing the Triumph twin ports on a drill press. Doug Hele told him not to mention it because the operator had been doing it that way for many years.
By May 1971 BSA was looking at a loss of 1m GBP so was hardly in the position to make any changes to the design.
I think the A70 was the only one with steel capped rods but not sure.
The 350 was a disaster because it was "designed" by Turner (who checked valve springs by stepping on them with his heel). Two broken crankshafts and one valve gear failure in 1500 miles. The cutaway picture of the engine shows the characteristic Turner sharp angle between the port and valve. Also, by '71 you think they would have figured out it was a bad idea to put the output sprocket between the clutch and gearbox.



The last of the a65's had steel capped rods, it depended what they had in the stores, a bit like iron oil pumps.
Turner was not a performance merchant, he hated the racing idea. BUT he did have a real result with the 500 twin in the 30's
then, what yankee maker would consider using overhead valves in a motorbike engine eh? Or even a foot gear change?

Re: The what if A65 67hp challenge. [Re: Mark Parker] #782205 08/22/19 5:34 am
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I think the non-return valve thing is often the pumps leaking at the joint. Dave's comment is interesting heads being ported with a drill press frown and confirming that an A65 with more hp than a T120 was not wanted let alone one to out perform the flagship threes.

The thing is, a well made hemi head motor can be a great thing. Chrysler still make brilliant Hemi V8s, they have a different power delivery to multivalve V8s, enormous bottom end midrange and then they scream in a very Don Garlits sort of way, Toyota make a multivalve V8 petrol it's smaller than the Hemis but very bland in comparison to the massively more powerful psycho nature of the hemi. The base version is 470hp Toyota's multivalve feels like 180hp.


mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782206 08/22/19 5:51 am
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With 6+ litres and fuel economy like that, hemi's are good compared to pent roof multi-valve motors?

When F1 start using hemi's again, i'll think they are comparable.

Re: The what if A65 67hp challenge. [Re: DavidP] #782207 08/22/19 6:39 am
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Originally Posted by DavidP
Originally Posted by Allan Gill

Costs just as much to make something properly as it does it make something incorrect.

Then why didn't BSA do it properly?
It always seemed to me that the A65 was like the Combat Norton,a desperate attempt to wring modern performance from an antique design. At least Norton improved the bearings after that fiasco. BSA didn't even bother to update their oil system.



Probably because they knew they were going to the wall and who promotes something that is going down the tubes.

Tony, part’s blown engine answers your question of how long would a 650 last with 67 horse power


beerchug
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782208 08/22/19 8:20 am
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Originally Posted by Mark Parker
It's not particularly hard to do the ports by hand. BSA could have done the ports at least to how they were designed rather than short cutting at the factory, it may have been saving them a little money and keep the A65 on parity with the Triumph twin which they also owned. In 1970 they knew the difference between the heads but didn't rectify the production, they could have had 8 more hp in 1971. In their day these bikes were among the fastest most powerful on the road, but they were about to be displaced, or by 1971 they were being displaced by the 750s and the power bikes from Japan.

It was hardly a time to throw away easy hp in what was a full-scale hp race. You can see this when the mighty Z1 Kawasaki turned up, it was called the King. It was developed as a 750 but Honda released the CB750 4, getting the jump. Kawasaki held off releasing their bike till they increased the displacement to 903cc the reason they did that was to sell bikes, they understood the power of power. Honda claimed 67hp Kawasaki trounced it with 82hp and 54.2ftlb, though it was heavy at 542lb. For perspective my 883cc A65 weighs around 360lb and produces 97hp and 71ftlb it also has a very wide power spread. It uses a bigger version of the oval port above, so I'm interested to see how that translates onto an otherwise stock engine.

BSA already knew how to fix all the problems with the A65, roller mains both sides would have reversed market resistance, 71 or earlier they had excellent steel capped rods, high volume oil pumps and they had the A70 showing great potential. But they sank money and effort into things like the Ariel 3. And also the 350s that were a good idea though eventually scrapped because of a shot to the foot.

The 350 was a missed opportunity, they could not get good power from it because the head design was poor, DH had made an error, easy to rectify with a new casting, but management told him no. So 34hp was the best they could ever get. The 350 Honda was already in the market with similar power, the BSA 350 could and should have made 45+hp, and it would have been a winner, it could then be more expensive than the Honda because it gave more, it had the advantage with a state of the art frame and running gear already. A company like Kawasaki would have made sure they had what they needed to get the power necessary. So rather than spend massive effort and money fruitlessly down these paths, BSA could have done three things, fixed the A65 engine completely, and at the same time, because its basically the same thing, developed the A70And the third, built at least a limited number of Rob North style Rocket threes, the frames were state of the art and exotic, cheaper to manufacture than the std frames. The threes also work extremely well at 850cc if they wanted to respond to the Z1 and Ducati's SS750 when they came along.



BSA could have done a lot of things but they had a board that were mainly bankers and technically illiterate "gentlemen of means & distinction "
I mean the board went against the decisions & advice of the entire engineering department and put the C 10 / C11 into production post WWII. a design that was obsolete , heavy & labour intensive.
The board vetoed the original A 50/65 design with a horizontal split crankcase because "it would not be BSA"
The board forced the oil filler on the OIF twin frame to go under the saddle thus loosing a lot of oil capacity because "Riders would accidentally put petrol into the oil hole"
The latter showed not one of them had every put petrol into anything cause a bowser nozzel will not fit.
When you have the decisions being made buy such a bunch , any fool with a slick tongue and a spreadsheet could get them to back any stupid idea.


Bike Beesa
Trevor
Re: The what if A65 67hp challenge. [Re: NickL] #782209 08/22/19 8:33 am
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Originally Posted by NickL
A massive slice of their market was the 'states.
It would have been more of a benefit to make the a65 more reliable and long lived than to uprate it's horsepower.
The average bloke who bought a bike wasn'r racing it, he was riding it once a week and poorly maintaining it.
His mates with triumphs could get away with not changing oil etc so he would do the same...........the beezer went bang.
They should have shut down in 1963 and moved production to the far east, that way they would have had local access to
a massive market and government funded factories/development. Competing with japan's zero interest rate for business at
that time was impossible, they could product dump anywhere in the western world with government backing, and they did.
Beezer was nothing compared to the yankee electronics industry they devastated.
The management at beezer were just selling it all off and getting out, they didn't want to make motorbikes, they wanted to
make money. Pi$$ing about modifying cylinder heads on an out of date engine that's been in production for 10+ years
is the sort of thing that makes firms go broke.
I understand the nostalgia and i love the old crates as well, but politics and economics etc. get in the way.


Been looking at why the board did things for a very long time.
The only thing I can see is all through the 40's, 50's & early 60's every one knew that the USA & the USSR would go hammer & tongs into WWIII
And WWIII would be big money for BSA as WWI & WWII had been, it is just that it never happened.
Everything BSA pought was a stratigically important industry in a war.

Also remember that motorcycles had never ever made BSA much profit.
The profits came from guns , powder metallurgy, coal handling , home furnaces, air conditioning, lathes, mills tooling , steel, coal mines and all the other things that BSA was into.
By the time the board realized that they HAD to make a profit from motorcycles it was too late ,


Bike Beesa
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Re: The what if A65 67hp challenge. [Re: DMadigan] #782210 08/22/19 8:47 am
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Originally Posted by DMadigan
Hopwood in his book states the attitude of the Managing Director that BSA and Triumph machinery must be equally prepared so it was unlikely they would have made the improvement to the A65. When Dan Macias visited the Triumph factory he saw they were finishing the Triumph twin ports on a drill press. Doug Hele told him not to mention it because the operator had been doing it that way for many years.
By May 1971 BSA was looking at a loss of 1m GBP so was hardly in the position to make any changes to the design.
I think the A70 was the only one with steel capped rods but not sure.
The 350 was a disaster because it was "designed" by Turner (who checked valve springs by stepping on them with his heel). Two broken crankshafts and one valve gear failure in 1500 miles. The cutaway picture of the engine shows the characteristic Turner sharp angle between the port and valve. Also, by '71 you think they would have figured out it was a bad idea to put the output sprocket between the clutch and gearbox.


BSA MOTOORCYCLES were loosing money.
The other divisions were making money, enough to pay down the motorcycle divisions debt . Why do you think the corperate criminal Dennis Poore quietly transferred these non motorcycling assets into his own company Manganese Bronze ?
The killer was the way the money morons had taken advantage of the post WWII British tax system to avoid paying any tax by debt financing every years production, a risky financial system that requires you to turn a profit each & every year.
As for not having the money to make last minute changes, steel capped rods, cast iron oil pumps, they were working away but the flagship fast bike was the A75 and making the A65 better & faster than the A 75 which was winning races & getting good publicity was never going to happen.

As for Mr Turners engineering, the less said about it the better.
What is oft overlooked that he was the persons who had resurrected Ariel a company that was bankrupt when he became the chief engineer but the real engineers at Ariel made his ideas work
He then went on to do the same thing to the again bankrupt Triumph, again because the real engineers made his designs work.
So to the uninformed & engineering illiterate members of the board Turner was a God that could fix anything and nothing he said could be questioned by anyone.
The problem was Sangster knew he was really only a stylist and allowed the real engineers under him to fix his short comings . The board did not and gave him absolute authority so they were on the road to dissaster.

Last edited by BSA_WM20; 08/22/19 8:55 am.

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Re: The what if A65 67hp challenge. [Re: Allan Gill] #782211 08/22/19 9:13 am
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Originally Posted by Allan Gill
Originally Posted by DavidP
And if BSA had actually done this to every production model they would have had to charge how much for each bike? They had enough trouble selling them at the price they charged.
Looks like a fun project though.


Costs just as much to make something properly as it does it make something incorrect.

Be interested to know what the difference in the blueprint head and the other heads. theres 2 casting/part numbers for the OIF 2 carbs heads, a few suttle differences between them, but never measured the ports..... too late now as both of them are modified.



20:20 hindsight is a wonderful thing Allan.
What we know in 2019 was not known in 1962.
We forget that all BEESAS were designed with slide rules.
It would be another 20 years before reliable computer modelling became available.
Port design changes had to be made in metal by hand then tested to failure a very slow & expensive process.
Look at the bore to stroke ratios, once they found one that worked it never got changed. you can trace most of them back to the 20's. A 65 sort of excluded.
We also have to remember that to the BSA board, their competition was Enfield, Norton and the failing AMC.
Untill the Honda 4 appeared there was no competition to the superiority of the British motorcycle because they were British and the Japanese will never be able to make a real mans motorcycle.
This was the attitude of the board, in fact it appears several times in minutes of board meetings.
So if you can sell all that you can make, why spend money to make it better ? , another attitude that appears in board minutes for decades .


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Re: The what if A65 67hp challenge. [Re: Mark Parker] #782212 08/22/19 9:26 am
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How long would it last with 67hp is an interesting question. For a manufacturer you want indestructability as a high priority, right along side the priority of finding the best hp.

Did you know what Rolls Royce did with the Merlin engine? 33 prototypes, before the first production model with 1035hp was used in Hurricanes and Fairey Battles, and then, it was very unreliable. But Rolls Royce started taking random engines from the production line and ran them at full power on the test bed until they failed, then when they could find the cause, they redesigned until they fixed it, and the Merlin became one of the most reliable aero engines ever, even with power boosted to 2030hp in some Spitfires. In 1944 they had a Merlin on the test bed with 2,640hp. From around 50hp per liter to almost 100hp per liter. Rolls Royce didn't even think that sort of output was remotely possible and were developing the bigger Griffin engine.

My 883 is putting out almost 110hp per liter.

I don't want to run my engines for hours on a dyno at full noise, but factories need to do it and make sure they are up to it, because customers somewhere are going to do it. Why modern cars and bikes have rev limiters. Reminds me of the framed poster in the Toyota workshop with a picture of a mechanic and a car, listing some of the things experienced technicians would carefully check on the pre-delivery of your new vehicle, the apprentice had crossed them all out and written in 'Rev Limiter'. You can actually beat a rev limiter by throwing things back a gear or two. We had a Corolla come in that had spat most of the valve actuating gear out, the lady had changed back to a lower gear to pass a truck, possibly from 5th to 2nd or 4th to 1st at a guess.


mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782215 08/22/19 10:54 am
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Originally Posted by Mark Parker
I think the non-return valve thing is often the pumps leaking at the joint. Dave's comment is interesting heads being ported with a drill press frown and confirming that an A65 with more hp than a T120 was not wanted let alone one to out perform the flagship threes.

The thing is, a well made hemi head motor can be a great thing. Chrysler still make brilliant Hemi V8s, they have a different power delivery to multivalve V8s, enormous bottom end midrange and then they scream in a very Don Garlits sort of way, Toyota make a multivalve V8 petrol it's smaller than the Hemis but very bland in comparison to the massively more powerful psycho nature of the hemi. The base version is 470hp Toyota's multivalve feels like 180hp.

The new Chrysler Hemi is not a true hemi but more like an oval using twin spark plugs...And The Chevy LS V8 can match or exceed a new Hemi in power using a wedge head combustion chamber with two inline valves..And the Chevy engine is less weight and more compact...

The A65 has a better head design than a Triumph ...Jim Rice in the 70's did ok on flat track racing with his 750 BSA until the XR750 Harleys got better tuned...At that time a Triumph 750 built by CR Axtell made about 72 HP. I don't know is that was crank or RWHP So the 750 BSA was making the same or a bit more..I don't know if flat track bikes were tuned to get every possible bit of power like drag race engines..


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782284 08/23/19 12:54 am
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Interesting thoughts here and makes me wish for another unit BSA twin.
Some time ago for my own amusement I wrote an "alternative history" essay in which AMC revived the Porcupine and gave two motors and spares to Eric Oliver in about 1955. By 1960 they were so developed that BMW rennsports were entirely outclassed and it was not until 1965, in my "history", that two-strokes came along.
Yes, dry sump, low c-of-g, and a motor that was at the beginning of its potential developement, as opposed to the RS. "By 1962", I wrote. "a four valve head was in the development sshop but not needed"...
Fun to make up a history in which one's favorites win.

Re: The what if A65 67hp challenge. [Re: Mark Parker] #782298 08/23/19 4:24 am
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I've driven Holdens with LS engines, not the blown one nor the LS7 427, but mostly at my work it was the Hemi in Jeeps and Chryslers . Highway patrol here now have the Holdens BMW and Hemis.

Didn't drive the Holdens much because we worked on the Toyata/Jeep side of the dealership. The hemi sounded much better to everyone, never saw anyone come back from driving one without a big grin, but we didn't pay for fuel I guess.

There's a good film on youtube of A70s being raced, they were definitely finding good hp. Just listen to Aldana's BSA. I think low 70s is what they had at the wheel, the F750 works 3s I think the best tested had 73rwhp. The best I've seen for a 3 was a 930cc at 87rwhp and that was following exhausting dyno tuning, which I guess is necessary to find the best settings, but you need money for that. The works Commando raced by Peter Williams around 1972-73 had 76 at the crank 67rwhp.

https://www.youtube.com/watch?v=fehu0WaPE6A&t=620s

While we are at it Peter Williams, brilliant guy in so many ways.

https://www.youtube.com/watch?v=a-SOXVVdIZ4&t=19s


mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782300 08/23/19 4:42 am
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I lived around the corner from 'crasher Croxford' for a while, used to see him about on his Guzzi.
Bloody nutter. Mick Hemmings rode that norton well too.

Re: The what if A65 67hp challenge. [Re: Mark Parker] #782305 08/23/19 5:46 am
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This brings up the question of what breaks next? At 40 HP the A65 was fairly reliable. With over 50% increase you have to start looking at all the failings of the design. You need RPM to make that power. Brings to mind Elvis Presley - "Shake, baby, shake!". The two bearing crank is going to need more support. The clutch hanging way out from the gearbox bearing needs support and the clutch itself with the basket supported by one row of rollers inboard and the pressure plate outboard is not up to the task. Valve train mass is going to be limiting.
Still your miles (kilometers?) off from the 90HP of the OW72 Roberts bike.

Re: The what if A65 67hp challenge. [Re: Mark Parker] #782306 08/23/19 5:54 am
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I hear it all the time, "Car engines used bushings on the crank."
The only one with which I am familiar enough to comment is the air-cooled VW. Yes, it used a bushed crank. No, it did not feed oil through the bush! It had oil feeds at two places along the crank. And, it was a wet-sump engine. And, if you wanted to rev it past about 4500rpm you had to dowel the crank so it wouldn't beat the bearings to death. Oddly enough, those engines could be built to deliver twice the HP and still be reliable.
BTW: My mid-71 A65 came with the crap-metal oil pump and alloy rod caps. Too little, too late.
There's a tale from Healy in Vintage Bike. They disassembled the first Trident they got at his shop and found casting sand inside the engine. So much for the artisans at Small Heath.


Stepping on others doesn't make you stand tall.

71 A65L "Zelda"
92 BMW K100rs "Gustav"
72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782313 08/23/19 10:51 am
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Automotive engines, auto/trucks/Diesels, use split plain bearings on all crankshaft journals.....Maybe some think those are bushings..The BSA crank bushing is rather wide and a small diameter, in comparison to other plain bearings that have a much greater diameter than width.
My first bike was a 1965 BSA 650 bought in 1972...I got it because it was much less expensive than a used Triumph because of the poor BSA reputation at that time..Same was true of British cars in the USA . American car industry and Harley was also suffering poor build quality for all the well discussed reasons...


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782315 08/23/19 11:00 am
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Loved that Aldana video, thank you.

Re: The what if A65 67hp challenge. [Re: Mark Parker] #782328 08/23/19 1:59 pm
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OW72, what an interesting bike. So the standard Yamaha was stuck in the mid 70s hp wise, 75-76hp, they needed 80+ to be in the race with the XR750s. The limitation was the head, it needed a new one that could flow more air, one with big valves 43 and 37mm with altered casting and altered valve angles. Yamaha spent money time and effort and built them.

https://www.mecum.com/lots/LV0116-228305/1976-yamaha-ow72-eddie-lawson-racer/

What I did with my A65 was to address its breathing limitation, but it doesn't need a new casting, though modification to the patterns, or even a non machined casting would allow even better breathing. I use 44.5mm inlets and 38-39mm exhausts. To improve the XR 750's 350 Gold Star based head, very clever tuners developed the oval port XR head. The same port I copied into my A65. It's a bit much for a 650, unless you were actually aiming for 10,000+ rpm but its great on the 883 and seems fine on the 750 though the head on our 750 flows a little less at around 190cfm rather than 200cfm which is a bit more involved to do.

So the stock A65 head can be modified to flow well enough for at least 85rwhp as I have with the 883. The 750 should be able to approach that as well though at higher rpm. The 750 could be running 12-1 compression when at the moment it's around 10-1. I ran the 883 at just over 12-1 for a while, I didn't realize that's what it was, its now 11-1 because even though it was ok with higher compression on pump gas it made me nervous.

The 90 degree configuration is like running a 46% stronger crank because that is the load reduction on it. The crank is supported on 3 bearings the 3rd is outside the alternator stopping deflection and primary misalignment, it also has an extra bearing behind the clutch to prevent the main-shaft deflecting. It's more difficult for the centre of a crank to flex when the extreme end is held, if you put a piece of wood between two bricks and push it the overhanging ends move up when the centre flexes down, clamping an end makes bending it in the middle more difficult. The A65 valve gear seems good at least to 9,000. The stock 473 cam profile retarded a little, to square it up, works really well, and it doesn't need excessively strong valve springs. An A65 like this with 190cfm heads running 12-1 compression according to a hp calculator should be able to make about 98hp at the flywheel at somewhere around 9000-9,500. Something might break, but the 883 doesn't break stuff anymore at that power level. (not that it's being raced)

With this small oval port head I was just wondering what it would do on an otherwise stock motor.


mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782329 08/23/19 2:08 pm
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Might have missed something earlier Mark (or dementors is setting in which is possible) so your now flowing a 30mm head? Not one that’s been opened up like on the 883?


beerchug
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782331 08/23/19 2:19 pm
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Yea a little version of the bigger oval port, I had it at 30mm with stock valve flowing around 143cfm now its 32mm with 42mm valve around 160cfm but the carb restricts it to 145cfm, a flatslide with smooth bore would give better flow. But I can use these 32VM round slides to see how it works, its a small port with higher velocity. Just need to build the bike.


mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782332 08/23/19 2:23 pm
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Wonder what you would get on cfm on the small port head, flowed, I've found that to give me the best power on the 650's


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Re: The what if A65 67hp challenge. [Re: Mark Parker] #782397 08/24/19 12:27 am
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The British bike industry was much more adventurous in what they made before the war. After the war Britain was skint and reverted to making singles, parallel twins, and villiers engined ring-dingers for people to get to work on. The shareholders wanted their dividends and refused to reinvest money when it was really needed, leading to 30hp twins being stretched by crude tuning to fragile leaky 50+ hp machines.

Doug Hele, who was a good engineer, had the triple ready to rock in the early 1960's, but the money men said no as the Bonneville was selling like hot cakes and they didn't want to rock the boat. It was a real missed opportunity imho. By the time the triple was needed, the money to build it was not there any longer.

What Mark is doing with his twin, Bsa could have done 50 years ago, Developement rather than ever wilder cams and higher compression ratios, and hoping the main bearings don't fail, the crank doesn't break, or the engine doesn't start throwing rods.

Re: The what if A65 67hp challenge. [Re: Mark Parker] #782398 08/24/19 12:30 am
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Mark.
I am doing the engine prep work on a 650/750 a65 for an outfit at the moment, it goes well for what it is.
He's just won the Queensland title on it and came 2nd last year in the aussie championship as a 'worked' standard 650.
He was only beaten by a 920 norton (totally illegal really) But, it made a lot of blokes look silly.
The 'new' motor will have an a10 crank in it, end fed etc.
As he has to comply with pre-63 regs he must use a modified single carb head which we have done, (a65 'Star' was around in 62)
he will be running a dcoe40 carb, so i've had stubbs welded on. He can run main venturis up to 34mm but i have 33's so we'll use those.
Up to now we have run a pair of 30mm or 32mm standard carbs, but he wants to use the weber as do i. It complies and i have experience with them.
I have a set of large inlet valves for it. (modified velo ones, they are quite nice)
Do you fancy doing the head up for me? No money in it as i do it for love! Classic racing is like that i'm afraid.
Just tell me to pi$$ off if your not interested. LOL.

Re: The what if A65 67hp challenge. [Re: DavidP] #782419 08/24/19 2:26 am
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Originally Posted by DavidP
I hear it all the time, "Car engines used bushings on the crank."
The only one with which I am familiar enough to comment is the air-cooled VW. Yes, it used a bushed crank. No, it did not feed oil through the bush! It had oil feeds at two places along the crank. And, it was a wet-sump engine. And, if you wanted to rev it past about 4500rpm you had to dowel the crank so it wouldn't beat the bearings to death. Oddly enough, those engines could be built to deliver twice the HP and still be reliable.
BTW: My mid-71 A65 came with the crap-metal oil pump and alloy rod caps. Too little, too late.
There's a tale from Healy in Vintage Bike. They disassembled the first Trident they got at his shop and found casting sand inside the engine. So much for the artisans at Small Heath.


Many blokes are riding their standard setup a65's quite happily, me included, with alley rods and a standard timing side bush. I certainly don't 'baby' my road bikes and i know
the racing outfit i prepped last year (also standard) gets used to 7-7500 often. I really think you suffer from a phobia about beezers. As i've said before, why not just sell it? (and buy another vw)
The artisans at beezer were renowned for 'doing the dirty' on triumphs wherever possible, human nature towards the competition i suppose. Chances are, the blokes at triumph would have done the same.
The bearing used on the a65 timing side is very similar to a car main with the exception of it not being split. Only aftermarket bearings were in fact a bronze bush. Either type work well if
installed correctly. Look at the racing history of bsa during the '50's when they produced the goldie if you need proof they could get a proper production bike to go, it won everything.

Re: The what if A65 67hp challenge. [Re: Mark Parker] #782421 08/24/19 3:16 am
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Maybe they should have opened the R&D shop in Oz instead of Slumberglade.
You blokes seem to be able to tweek anything. Toss another crank on the barby, mate. laugh


Stepping on others doesn't make you stand tall.

71 A65L "Zelda"
92 BMW K100rs "Gustav"
72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782423 08/24/19 3:31 am
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No rocket science David, just a sense of humour and time.

Never tried the crank on the barby though hmmmmmmmmmm

BTW i'm still classed as a pommie, iv'e only been here 20 years!

Re: The what if A65 67hp challenge. [Re: Mark Parker] #782434 08/24/19 7:29 am
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Nick so he's ok using an A10 crank but not a twin carb head, they make ridiculous rules. Are you sure twin carb heads were not available as a competition option? But yea I'd love to look at that head.


mark
Re: The what if A65 67hp challenge. [Re: NickL] #782439 08/24/19 11:21 am
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Originally Posted by NickL
No rocket science David, just a sense of humour and time.

Never tried the crank on the barby though hmmmmmmmmmm

BTW i'm still classed as a pommie, iv'e only been here 20 years!


Don't know about the crank on a barbie , but I did know a bloke who had a goldie rod on his power hacksaw .


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Re: The what if A65 67hp challenge. [Re: Mark Parker] #782442 08/24/19 11:54 am
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Around 2000 I bought a 55 BSA A10 basket case on eBay... Disassembling the engine it had a brand new crank , the "better " A10 rods and GMP pistons of about 10-1 compression..I got on this site to read about A10's and there was a lot of discussion on oil pumps and poor oil pressure when warmed up..I found a nice cast iron pump and carefull checked bearings clearances on the timing side bushing and rods...I drilled a passge and tapped it for a remote oil pressure gauge...Added a "357" cam , found a decent head and has the magneto rebuilt....Had a bit of a tuning issues with the cam but got it to run well except for a bit reversion around 4500 rpm. It always had good oil pressure when warmed up even at lower rpm's..I like to say it was one of the best Brit bikes I owned...


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782485 08/24/19 10:59 pm
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Originally Posted by Mark Parker
Nick so he's ok using an A10 crank but not a twin carb head, they make ridiculous rules. Are you sure twin carb heads were not available as a competition option? But yea I'd love to look at that head.


That's great Mark, thanks very much, i'll pm you and send it down. There's no panic, he won't be out again until Feb/March time.

The a10 crank is perfectly legitimate, the a10 had been produced since mid 50's. The a65 wasn't used in competition much until 64/65 anyway.
The twin carb head did not come about until 63/64 it was never available for the 'star twin'
which was the first a65 to launch and the only one in 1962.
I have no problems with sticking to the rules. i wish others would though. The 'norton atlas' that won the aussie title
was built using a set of those new cases that are about an inch thick etc etc. About as much an atlas as a gs1000.

Tony, i had an a10 super rocket as a kid and loved it, thrashed the living daylights out of it, never had any serious problems.
That had 10.5s-1's TT carb sweptback pipes with small bore goldie silencers etc etc. Great old iron.

Re: The what if A65 67hp challenge. [Re: NickL] #782490 08/25/19 12:32 am
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Originally Posted by NickL


Tony, i had an a10 super rocket as a kid and loved it, thrashed the living daylights out of it, never had any serious problems.
That had 10.5s-1's TT carb sweptback pipes with small bore goldie silencers etc etc. Great old iron.


it looked like this...best Triumph I ever owned, lol Hot rod 37 Chevy truck in background.


[Linked Image from live.staticflickr.com]


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782507 08/25/19 5:40 am
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The picture of the A10 reminded me of a conversation I had with one of our colleagues about petrol tank size in the American market. Large country with long distances yet we loved those tiny fuel tanks. Only Norton offered a touring size tank.

I think several issues are at play here:
1) Vibration limited the ability of most people to ride an A65 for hundreds of miles non-stop. 2 gallon fuel tanks forced one into taking regular breaks (& most were surely grateful for it). It also forced the rider into giving the engine a break as well.
2) Engine displacement has always been a sales factor for Americans. The small fuel tank makes the engine appear as large as a Sportster.

Perhaps it's fortunate that the A65 died so suddenly. The T140 died many deaths before it's last.


Ray Elliott
---
A65, A70, A75, T120, T140, T150, T160
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782511 08/25/19 6:18 am
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I don't know really Ray, my old crate does vibe a bit but i was out last week and rode it at 70-80 mph for around 200 miles with only one stop for a quick leak. (me, not the bike.)
Bursts up to 90+ indicated, the only thing that slowed me was one front turn indicator rotated on it's stem.......... i think
the late ones with the scalloped flywheel were better balance wise, they were supposed to be 'dynamically balanced' in the factory
but i doubt that. I don't think it's any worse than my t120 at that sort of speed, maybe a little more 'tingly' but you don't have to grip the bars that hard.
Maybe when i strip it again i'll have the crank 'dynamically balanced' as everyone seems to think it makes a marvellous improvement, i only did mine statically on knife edges.
I don't like small tanks, when i go for a ride i don't want to be stopping every 100 miles for fuel it would stop me riding on the best bike roads here.

Re: The what if A65 67hp challenge. [Re: NickL] #782516 08/25/19 7:51 am
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Originally Posted by NickL

i think the late ones with the scalloped flywheel were better balance wise, they were supposed to be 'dynamically balanced' in the factory
but i doubt that.

I very much doubt it as well. The clue to whether a crank's been dynamically balanced is whether there are any holes drilled asymmetrical to the centre line of the flywheel. The attached photo of a late 'scalloped' crank shows all the holes are drilled symmetrically, including interestingly, the side cheeks which you don't often see. One thing that is in the favour of the later crank's balance, is that it has been machined all over the side cheeks, thereby giving greater control of any out of balance asymmetric forces.

[Linked Image from i.postimg.cc]

[Linked Image from i.postimg.cc]


1957 BSA A10 Spitfire
1971 BSA A65 Firebird
1971 BSA A70 Lightning
1975 Norton Commando
1961 Norton 99
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782521 08/25/19 9:37 am
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The scalloped flywheel is new to me ,didnt know that, my 71 has the full circle, since it was dynamically balanced 6,000 miles ago there have been no light bulb failures so it might be worth the bother Nick.


71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782528 08/25/19 12:21 pm
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My A10 shown above had a Mustang tank that was popular in the USA years ago..Stripped down to look like a drag bike ....I don't remember the actual gearing but it vibrated less than many at 4500 rpm in high gear....After 1-1/2 hours or so riding any bike I'm ready to take a short break so fuel capacity isn't an issue.
I sold it to a guy who owned a seafood joint in Mississippi in 2005...That A10 is the only bike I ever sold that I want back....


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782595 08/25/19 11:17 pm
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My A10 was bought in boxes for 25 quid and came home on a double decker bus.
3 guys gave me a hand and the conductor allowed us to stand the frame on the rear open entry area of the bus.
It never looked very sexy but it did go well. It went to the elephentreffen (elephant rally) in germany a couple of times
with a sidecar on it too. At one time I had a steib sidecar on it which was stolen, they were quickly detachable and some bugger did!

Re: The what if A65 67hp challenge. [Re: Mark Parker] #782652 08/26/19 11:53 am
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The stock 650 Yamaha head had valves at 76degree, the OW72 had steeper valve angles at 56degree. Yamaha spent millions on a head to get into the 80hp region.
Does anyone know what A65s are? I think they may be around 60degree?
They seem to be referring to the angle between the valves.
And Triumph?


mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782674 08/26/19 4:32 pm
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The A65 has 37 degree valve angles or 74 degree included. To reangle the valves to 54 degrees the chamber would have to be much flatter. I have 35/41mm valves in an 80mm bore with 35 degree valve angle and the chamber is 1.126" deep. Changing to 26 degree the chamber is 0.107" shallower and the valves are really close to each other and the cylinder walls.
I think the 35 degree valve angle is what I measured off the Wiseco XS750 piston.

Re: The what if A65 67hp challenge. [Re: Mark Parker] #782676 08/26/19 4:37 pm
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A TSS style head would be a nice thing to have cast. In the dreams of many I suppose though.


beerchug
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782677 08/26/19 4:59 pm
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I drew plans for a 4 valve but there was little interest. A proper two valve head is cheaper and has at least some chance of running in the historic races. Why they allow a four valve Triumph but not a four valve BSA just because the year of manufacture differs is beyond me.
Mark - Here is the OW72 intake port, something like yours?
https://thexscafedotcom.files.wordpress.com/2017/12/ow72-10.jpg?w=1000

Re: The what if A65 67hp challenge. [Re: Mark Parker] #782685 08/26/19 7:44 pm
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Dave, I don’t remember your plans for the 4valve per chamber head. It’s sometjing I’ve fancied the idea of for a long time, but it’s a lot of work and changes in rocker geometry. Any Movement with the 5 spd box?


beerchug
Re: The what if A65 67hp challenge. [Re: DMadigan] #782693 08/26/19 10:50 pm
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Originally Posted by DMadigan
I drew plans for a 4 valve but there was little interest. A proper two valve head is cheaper and has at least some chance of running in the historic races. Why they allow a four valve Triumph but not a four valve BSA just because the year of manufacture differs is beyond me.
Mark - Here is the OW72 intake port, something like yours?
https://thexscafedotcom.files.wordpress.com/2017/12/ow72-10.jpg?w=1000


When the classing is policed, i have no objection to allowing 3 cylinder motors or 8 valve twins in the applicable periods.
What is wrong is things like allowing 900cc weslakes and 920 triples and 1200cc hondas in pre 72 racing, they didn't exist in 1972.
Rickman sold an 8 valve kit for triumphs in 69 or 70 so perfectly legitimate. Norton commando/atlas cranks were around and people used them,
not 1 piece billet machined en40 things or belt drives and mikuni flat slide carbs. etc etc.
Why not just enter a new Ducatti as a Vincent? it's a v twin so must be the same eh?
If you had done the 4 valve head for an a65 in 1971 it would be allowed in that period/racing class now. Unfortunately, you did it in 2016 so that's
when it's eligible for classic racing.
Go race a modern bike if you want to stay up to the minute. My 2c.

Re: The what if A65 67hp challenge. [Re: Mark Parker] #782697 08/26/19 11:16 pm
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Hard to see what that OW72 port does Dave. I copied the XR750 port. My vacuum cleaners say 200cfm @ .410 valve lift @28"w. Hp calculator says 95hp at the crank, from a Street/strip engine 114hp Super stock engine. Which I guess is just a hotter version. On a 750 that means 10,000rpm, on the 883 it means 8,300rpm estimated rpm. Mine made 97hp @ 7780rpm but was not being revved enough for the graph to go over and start falling off. It was too lean by miles, had restrictive mufflers and a spark advance that was guessed at. With the mixture in the ballpark and better mufflers plus the ignition optimized I expect it would have better power. A 750 can rev more though I don't think we have revved one past 9,000.

This is the port on the 883 which probably has more flow than needed, which I guess doesn't matter as the thing has very strong bottom end and midrange anyhow. The 750 is more or less the same but slightly smaller and less radical for almost the same flow. The new 4V Triumph heads flow 180cfm by comparison.

[Linked Image from i.postimg.cc]


mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782710 08/27/19 1:11 am
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Whats bolted onto that sexy flange? Round to oval?


71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
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Re: The what if A65 67hp challenge. [Re: Mark Parker] #782716 08/27/19 1:56 am
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The transition to oval is in the bolt on manifold, yes.

I was just testing a Thunderbolt head, minus the manifold, the port is shorter than a stock Lightning and only 27mm but it flows better. I doubt it would with the manifold on. But the port is drilled a bit better. It's a bit of a wake up call really. Cannot judge what a port will flow by basic specs of valve size and diameter. Measuring flow only really measures how easy air can flow through a port, so air goes through the manifold less Thunderbolt head easier than the Lightning, and faster. what happens with carb added changes the equation though. And carb size matters.


mark
Re: The what if A65 67hp challenge. [Re: NickL] #782721 08/27/19 2:56 am
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Originally Posted by NickL
Originally Posted by DMadigan
I drew plans for a 4 valve but there was little interest. A proper two valve head is cheaper and has at least some chance of running in the historic races. Why they allow a four valve Triumph but not a four valve BSA just because the year of manufacture differs is beyond me.
Mark - Here is the OW72 intake port, something like yours?
https://thexscafedotcom.files.wordpress.com/2017/12/ow72-10.jpg?w=1000


When the classing is policed, i have no objection to allowing 3 cylinder motors or 8 valve twins in the applicable periods.
What is wrong is things like allowing 900cc weslakes and 920 triples and 1200cc hondas in pre 72 racing, they didn't exist in 1972.
Rickman sold an 8 valve kit for triumphs in 69 or 70 so perfectly legitimate. Norton commando/atlas cranks were around and people used them,
not 1 piece billet machined en40 things or belt drives and mikuni flat slide carbs. etc etc.
Why not just enter a new Ducatti as a Vincent? it's a v twin so must be the same eh?
If you had done the 4 valve head for an a65 in 1971 it would be allowed in that period/racing class now. Unfortunately, you did it in 2016 so that's
when it's eligible for classic racing.
Go race a modern bike if you want to stay up to the minute. My 2c.


And to add to that is is boring for the spectators particularly when you are watching something that you know could not be made to perform that well in it's day make real period racre bikes of that period look stupidly slow.
Back in the 80's we tried really hard to get Bantam racing established as an introduction to historic racing.
Don Nolan worked for Telstra and was always up bush so he dug out a lot of old time race bikes & the bloke who rode them in the 50's & 60's but it fell flat on its face because of all of the clowns with massive egos who spent $ 30,000 grafting most of a TZ into a Bantam case and ended up with a bike that dope burning Manx Nortons could not catch . If there was money to be made you could understand it but all you got was a trophy with was usually a period trophy repurposed.
Thus the category died and historic ( now called period ) racing has been going backwards ever since.


Bike Beesa
Trevor
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782756 08/27/19 3:14 pm
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I see your point that my 750cc 90 degree XS crank with CR500 rods A65 would not be period correct. According to your rules, Mark's port would be illegal since it was not done back then either, nor Hill's 750cc aluminum cylinder and five speed gearbox. Where is the line is drawn, what was done, could have been done or something done to one make applied to another? If the rules are kept strict you end up with one make racing, whichever was the winning bike back then would be the bike to have.
I know someone who maintains circle track cars. Only very rich people race them now because unless you have the latest trick parts you are not competitive.
The four valve A65 head was to get more performance, not necessarily for racing although since Rickman already applied it to the Triumph T120 they could have easily applied it to the A65. An alternative is a better breathing two valve, cheaper to produce (within the realm of specialty parts) and (hopefully) more commercial interest. Since I want it to be a 750cc it needs a new 80mm cylinder and to keep it together, the four outer base studs are brought up through the head.
Allan, the five speed is on hold at the moment because I have to get the Wenco racer together for the Cachuma rally. Rather than having the gear shop dive in on ten or so sets of gears I am going to make the first set in aluminum to thoroughly check it out then make them in steel myself. Their setup costs are a bit high and since I have the machines to do it I might as well try. They did not sound completely confident about the special addendum gears and with the wider ratio set you wanted there are more of them.

Re: The what if A65 67hp challenge. [Re: Mark Parker] #782758 08/27/19 3:29 pm
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Advantage with the 4 valve is the ability to use lighter valves, possibly also valves with slimmer stems (standard Brit ones are quite meaty compared to some Japanese valves, the TSS also looks to maintain 5/16” stems. This will effect flow, even tapered after the valve guide would be an improvement I would think.


beerchug
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782813 08/27/19 10:56 pm
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Most Japanese engines have a bucket or something taking the side load off the stem. You would have to compare a Japanese rocker operated valve engine to see what stem size was engineered to work with a rocker setup. My Rickman four valve had stout 7mm stem valves. I changed them to XR200 5.5mm stem valves and roller rockers.
5/16" stems were the standard before any real engineering went into the valve train parts.

Re: The what if A65 67hp challenge. [Re: Mark Parker] #782815 08/27/19 10:59 pm
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I don't think how you port a standard head would breach any rules for classic racing. It's what people did. And it's also what makes using these old things rewarding. Anyone can go spend money and buy a 200mph bike. Changing a crank to 90degree is something that could have been done, and gives quite an advantage in respect to rpm, smoothness reliability and performance, but it seems to be quite acceptable. If people race an old bike it's way better if they can do it with out breaking stuff, especially cranks. Also better for spectators at events if the bikes you went to see keep running. 5 speeds were also available for A65s back in the day, so it shouldn't be a drama to use one today, even if the ratios are better and the clutch hub is splined. The spline doesn't make the thing faster but it means the bike won't be sidelined with a spun taper and sheared key.


mark
Re: The what if A65 67hp challenge. [Re: DMadigan] #782818 08/27/19 11:39 pm
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Originally Posted by DMadigan
I see your point that my 750cc 90 degree XS crank with CR500 rods A65 would not be period correct. According to your rules, Mark's port would be illegal since it was not done back then either, nor Hill's 750cc aluminum cylinder and five speed gearbox. Where is the line is drawn, what was done, could have been done or something done to one make applied to another? If the rules are kept strict you end up with one make racing, whichever was the winning bike back then would be the bike to have.
I know someone who maintains circle track cars. Only very rich people race them now because unless you have the latest trick parts you are not competitive.
The four valve A65 head was to get more performance, not necessarily for racing although since Rickman already applied it to the Triumph T120 they could have easily applied it to the A65. An alternative is a better breathing two valve, cheaper to produce (within the realm of specialty parts) and (hopefully) more commercial interest. Since I want it to be a 750cc it needs a new 80mm cylinder and to keep it together, the four outer base studs are brought up through the head.
Allan, the five speed is on hold at the moment because I have to get the Wenco racer together for the Cachuma rally. Rather than having the gear shop dive in on ten or so sets of gears I am going to make the first set in aluminum to thoroughly check it out then make them in steel myself. Their setup costs are a bit high and since I have the machines to do it I might as well try. They did not sound completely confident about the special addendum gears and with the wider ratio set you wanted there are more of them.


Mark's port work would not be illegal, many blokes used weird and wonderful techniques on performance bikes back then.
You could have used a 1972 xs crank if you had one with corrillo rods, though in an a65 i doubt the work would be worth the effort.
Devimead were producing 750 and 850 kits so Johns barrel would be ok. Several blokes fitted 5 speed quaife boxes too.
My outfit had a 6 speed shaflightner box in it with a morgo pre-unit triumph in 1974, before i bought it.
Anything that was available at that time may be used. You probably could get away with your cylinder head if it looked more home made,
but they were not a commercially available item back then. I raced against plenty of 750 Weslakes in 75-76 and a few 850's, at that
time they were not fantastic and blew up as often as other engines back then. We beat plenty of them on the old Morgo thing.
It's only when the jap tz's came in that it became a race of one type. They just killed the sport completely.
Look at the winning results for the classic series in the NZ. They police the rules properly, all sorts of genuine period bikes compete.
If you turn up with a 9 stud triumph and it's a pre-58 race you'll be allowed to race but will be given no placing. If you try getting
away with using a 5 speed box in a pre unit, you'll be pinged. Admittedly, you can't stop the Titanium rodded $2,000,000 Manxes
and G50's etc but generally they have a very good system. When i started racing 'Classic' sidecars in 1990 i was amazed that so
much non period gear was allowed, it got worse and ended up with the, 'he who has most money wins' thing.
Many of the racers don't prepare their own bikes anymore, it's gone away from the whole concept of club level racing, which was
what it was supposed to be about. If you look back at the 60's all the makes had their victories at one class or another so i disagree
with your 'one bike would be the winner' thing.

Re: The what if A65 67hp challenge. [Re: Mark Parker] #782820 08/27/19 11:50 pm
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Originally Posted by Mark Parker
The transition to oval is in the bolt on manifold, yes.

I was just testing a Thunderbolt head, minus the manifold, the port is shorter than a stock Lightning and only 27mm but it flows better. I doubt it would with the manifold on. But the port is drilled a bit better. It's a bit of a wake up call really. Cannot judge what a port will flow by basic specs of valve size and diameter. Measuring flow only really measures how easy air can flow through a port, so air goes through the manifold less Thunderbolt head easier than the Lightning, and faster. what happens with carb added changes the equation though. And carb size matters.



Maybe we weren't so stupid using the t'bolt heads eh?
We also had better results years ago on the morgo triumph using the T110 head with stubbs rather than the splayed port t120 one.

Re: The what if A65 67hp challenge. [Re: Mark Parker] #782829 08/28/19 3:10 am
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I just added 12cfm to the Thunderbolt port and its still 27mm,with no fill on the floor. I think the best stock Commando heads are around 123cfm, without checking calibration this is probably better. I hope your welded on stubs are not too long Nick.

Added another 11cfm by egging the port out, its still very small with stock valve. And it is not smooth nor has it any fill on the floor. It needs another 15cfm. Easy port to work on.

[Linked Image from i.postimg.cc]


So I opened the seat area a little for a 42mm valve and reshaped a little which netted about 1cfm. So I tried a bellmouth on the port, It is bigger than the port, even squashed a little to match the oval, but it still leaves a step. Another 15cfm or so. So what goes on the port makes a difference. If it doesn't lose flow with manifold and carb on a race engine with high compression and decent exhaust 80hp might be possible. The port is still relatively small 28X32.5 it could be made a bit bigger. I need to re-calibrate the rig, to get exact figures, but it seems better by around 44cfm, though I didn't have the bell on the stock port, which would mean about 30cfm. I'll fill the floor a little and see what a better bottom radius does.


[Linked Image from i.postimg.cc]

Last edited by Mark Parker; 08/28/19 9:08 am.

mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782840 08/28/19 6:03 am
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Mark, try if you can to get hold of a small port lightning head and check the values, unlike the later leads there is already a better turn radiusnonly the valve. It would be a good comparison against that thunder bolt head?


beerchug
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782845 08/28/19 7:01 am
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The stubbs are about 2 inches long, they have to splay out a few degrees too.
https://imgur.com/KyvNtrX
https://imgur.com/279izLk
https://imgur.com/Os6M7gB
https://imgur.com/wq18HiQ
https://imgur.com/TjD7SHJ
https://imgur.com/b5g7CwX

As i said, it's as rough as guts at the moment, i've just had the stubbs welded on and made a start hacking the roof away. Brutal i know.......
The mating part of the manifold will be another couple of inches long, this will give about 300mm from bellmouth to valve.
Old school thinking i suppose, but it can change if you think it would be better. I was just going along the lines of my old ones.
https://imgur.com/LEQRzc1

Last edited by NickL; 08/28/19 7:56 am.
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782852 08/28/19 9:33 am
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Ok, is he using alcohol (in the bike)? What I have at the moment is a small high speed port, if it stays small it should pull from lower rpm and if it flows good with the carb it should pull to around 8,000. Not sure what a hotter than 473 cam will do though. Except if the port is small it will get velocity earlier to overcome reversion of a late closing inlet and or big bore headers.


mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782857 08/28/19 10:54 am
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No methanol, i don't want to go that way with a standard A10 crank, i don't think
it's up to it and i have no experience using alcohol, i always ran petrol. Much to
many people's disgust.
The cam is not one i'm familiar with so until i clock it up, i can't comment.
As it's one of Ivan's i suspect it uses similar to chevy profiles, he grafted one of
those onto the inlet of my old one. I can't ask him now as he died a few years ago.
The head that's on it responded well to decreasing the port size and raising the floor,
with the motor as is, a 650. The proposed blood line is around 6800 rpm with the
a10 crank. If and when he uses the offset norton one it can go up a bit, maybe 7500
but i always got better lap time with earlier changes, around 6800-7000. The cam
has loads of overlap so mid range is very good and it's late i/l closing so he has a
revlimiter set at 7250 at the moment otherwise it just keeps pulling, and he's overdone
that a couple of times with the consequent result. I've only been involved with it for the
last year or so, so i've had to get the thing reliable and sort out heaps of other stuff.
He's a good rider and the thing handles well, the makings of a very good package.
In the last year he's done very well and is keen to step up a little. As a 750 it should
be more up to the task of winning the aussie title, he needs more corner exit grunt etc.
The small motor needs to buzz a bit too much which costs him traction. Not much i can
do about that so a little bigger we go. (it's like deja-vu for me)

I think it may be an idea to send you down the carb and inlet manifold setup when i've got it
finished as well, that way you can see how the setup works. (Or fails to work!!!)

Re: The what if A65 67hp challenge. [Re: Mark Parker] #782858 08/28/19 11:03 am
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I may try putting a large allen bolt through the crank to stiffen it up a bit
something i did with the old triumph years ago. Any extra strength there
is worth a go. Offsetting is the better way to go though, i know.

Re: The what if A65 67hp challenge. [Re: Mark Parker] #782861 08/28/19 11:56 am
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Can you get the radiuss on the crank rolled anywhere up there? This little port is looking like it would be good, not that I've ever run a motor with this small a port. If it's 160cfm it shouldn't run out of breath with a 473 cam till probably 8,000 depending on the pipes. The manifold would be good to have, the carb maybe doesn't matter so much because its what it is, we could try different venture sizes and see what they do on the bench for curiosity. The Thunderbolt port goes into the bowl area better than the Lightning, its smoother. I wonder what the difference is between a stock Thunderbolt and Lightning on a dyno, I know the factory claim different power for them, but I put a Thunderbolt motor in my plunger A10 and latter switch to a Lightning head without noticing much, if any difference. What was a huge difference was between the A10 and the A65. The A10 was a lovely thing but threw a rod and I couldn't get bits.

Allan I don't have one of those heads, it would for sure be very interesting to test one.

Last edited by Mark Parker; 08/28/19 11:58 am.

mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782907 08/28/19 9:16 pm
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In the long term I will set a rig up for flow testing myself, I’ve done a few different heads all different and all respond differently. All good but in different ways. But to get a respresentative comparable they need to be checked on the same rig, I’m sure a rig that I set could give different readings to yours.


I may have a spare head which having good “standard” ports but probably needs more effort on it than I was willing to spend to make t worth putting on a bike. My intention was to do some experiments with it and see what I could learn from playing about with port shapes. I don’t think it even has any guides in it. Let me know if it’s of any interest and if your having anything being shipped from the UK any time and we can sort something out.


beerchug
Re: The what if A65 67hp challenge. [Re: Mark Parker] #782934 08/28/19 11:56 pm
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Thanks Mark, i'll get the head and bits sent down as soon as i can.
I'll investigate getting the crank radius's and journals rolled and maybe
nitrided too. I've dug out a new set of srm springs and some new exhaust valves,
PM guides and those big inlets. I'm waiting for collets and cups etc.
Unfortunately i've just landed a couple of electronic jobs so this will have to
take a back seat for a while. I'm a glutton for punishment, i'm supposed to be retired!
Just love to fiddle about and it keeps my brain working, well sort of...........

Re: The what if A65 67hp challenge. [Re: Mark Parker] #782945 08/29/19 3:14 am
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Ok. My Thunderbolt experiment is a bit less than the 32mm Lightning after recalibrating and checking both, it was reading a bit high which doesn't matter that much because it was showing gains and losses, it had a loss with the 42mm valve when I opened the seat to it. And I had to reshape the area a bit to get it back. Why something to measure with is so useful. The thing is so particular on shape.

Anyway I've filled the floor to see what that does before attacking it again. It will be interesting to see what filling on its own does, how much difference that bottom radius makes. Then I'll try going bigger after that. Though how the port is now would be a big gain on a road bike with a couple of carbs on it.

Update:

With fill on the floor I managed to lose 1-2cfm, curve was too sharp, fixed it to end up with about +10cfm without the bellmouth, and +7cfm with it. Highlighting the advantage of being able to measure. The curve probably had the air breaking away from the edge. It would be good to be able to see the air going through the port and see where disturbances are. It's now flowing pretty much the same as the 32mm Lightning but probably smaller volume. To get more probably means welding on stubs and going bigger plus going bigger with the valve.

This head might work on an A65 engine in a Fury/Bandit frame as the carbs would fit between the frame rails. That could be a pretty cool thing esp with a smooth 90degree crank and double the Fury's hp.

This is the Triumph version, shows why the Lightning head wouldn't fit.

[Linked Image from i.postimg.cc]

Last edited by Mark Parker; 08/30/19 4:29 am.

mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #783904 09/10/19 11:37 am
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Finding out more on the Thunderbolt head. The ports are biased toward the pushrod tunnel so can break through into that quite easily. The other side can be widened quite a bit. I'm trying to scale the XR 750 port to the 42mm valve in the BSA head. I'm testing at .385" valve lift and widening the port this morning has upped flow to 155.6cfm with a bell. From scaling the measurements I need to lift the floor more. Where the pushrod tunnel breaks through doesn't need to be so thin, making it much thicker there would not interfere with the pushrods. Without the bell its up to 146cfm to the std ports 108 or the std Lightning's 109cfm. I want to see if I can get 170cfm through this little 42mm valve. Testing this morning had the break through area covered but very un-smooth, when it's smooth it will be better.

155cfm should enable 73hp in a stockish engine or 80hp in a high compression race engine, both around 8500 in a 650 or 7,500 in a 750, according to the estimated hp calculator based on air flow.

Seeing filling the port is the next step looking for more flow, if its there it will be a double win as a smaller port will be better in the midrange.


mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #783909 09/10/19 12:58 pm
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Dang, dude, you sure come up with nice stuff...


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Re: The what if A65 67hp challenge. [Re: Mark Parker] #783952 09/11/19 2:03 am
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Filled the floor and went from 156 to 153, always exciting to go backwards frown A couple more goes at it got it up to 159.3cfm with the bell, 149cfm bare all @ .385" lift @ .410 its 162cfm with the bell. The floor is not anywhere near smooth and needs some fill in places. So the Thunderbolt head is doing the business. A 50% increase in flow.

Update; after a bit more fiddling 165 @ .384" lift with the bell. 152.9 bare. A bit more JBweld on the floor. I'll try some bolt on manifolds and use 34 or 36mm carbs. This is better than the 32mm Lightning head, similar to a 34mm Lightning type.

[Linked Image from i.postimg.cc]private image upload

Last edited by Mark Parker; 09/11/19 4:45 am.

mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #783972 09/11/19 11:03 am
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Mark this may be of interest....this comment from a tuner of modern 4 valve racing bikes...I don't know if the "tumble" he mentions can be applied to two valve engines. Honda has written some info on it..It goes beyond air flow to increase power and make a wide powerband..I believe in simple terms it's using turbulence to increase air flow without the need for large ports...

Quote
Ducati utilizes tumble, not swirl designs, to an awesome degree.

Those who play with their modern heads say they look weird on the flowbench, but it’s super easy to mess them up using traditional techniques. We’re talking engines that make 3.3hp/ci, NA, on pump gas, meet emissions, and have long service lives, and traceable power curves. Compression is over 12:1 on pump gas with bore sizes up to 4.5” on their twins.


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Re: The what if A65 67hp challenge. [Re: Mark Parker] #783976 09/11/19 12:30 pm
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Maybe its how the charge enters the cylinder.


mark
Re: The what if A65 67hp challenge. [Re: Hillbilly bike] #783984 09/11/19 3:22 pm
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Without increasing the port size on the right hand port, why dont you fill the port with modling clay to see how small you can get it before air speed drops off? As ive mentioned previously I have had good results just by filling the port floor and nothing else, even on the small port head.

Originally Posted by Hillbilly bike
Mark this may be of interest....this comment from a tuner of modern 4 valve racing bikes...I don't know if the "tumble" he mentions can be applied to two valve engines. Honda has written some info on it..It goes beyond air flow to increase power and make a wide powerband..I believe in simple terms it's using turbulence to increase air flow without the need for large ports...

Quote
Ducati utilizes tumble, not swirl designs, to an awesome degree.

Those who play with their modern heads say they look weird on the flowbench, but it’s super easy to mess them up using traditional techniques. We’re talking engines that make 3.3hp/ci, NA, on pump gas, meet emissions, and have long service lives, and traceable power curves. Compression is over 12:1 on pump gas with bore sizes up to 4.5” on their twins.


quite possibly taking into account the time to pressure equalisation when the valve starts to open and then how much is still flowing when the valve is being closed. something that cant be determined on a flow bench with a fixed valve opening.

Using modling clay you could try different port shapes to find what shape is best with smaller valve openings.


beerchug
Re: The what if A65 67hp challenge. [Re: Mark Parker] #783987 09/11/19 5:45 pm
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There's info on the Honda technical paper site. I believe you have to register to use it....The "tumble" is created in part by the piston shape...It's quite complicted, too much so for me...

Tumble


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Re: The what if A65 67hp challenge. [Re: Mark Parker] #783997 09/11/19 7:10 pm
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Lifted from the Honda site

"Summary

The combustion chamber shape of an engine with high compression ratio, long stroke, high-quantity cooled EGR, and retarded intake-valve-closing specifications was optimized to increase the EGR limit and minimize unburned loss and time loss with the aim of enhancing the brake thermal efficiency of a stoichiometric gasoline engine. A piston shallow-dish shape was adopted to optimize the tumble center and the piston top surface distance from the spark plug, and the combustion chamber peripheral shape was optimized to minimize unburned loss. The resulting enhancement of the external EGR rate limit and increase in combustion speed reduced both time loss and unburned loss, and achieved a brake thermal efficiency of 45.2%."

I think the Key word," long stroke" needs more detail, is everything oversquare considered short strioke.?
Exhaust Gas Recirculation = EGR


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Re: The what if A65 67hp challenge. [Re: gavin eisler] #784008 09/11/19 11:08 pm
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Originally Posted by gavin eisler


I think the Key word," long stroke" needs more detail, is everything oversquare considered short strioke.?
Exhaust Gas Recirculation = EGR

In the recent past Honda 4 cylinder car engines were/are longer stroke than other manufacturers...


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: The what if A65 67hp challenge. [Re: Mark Parker] #784009 09/11/19 11:11 pm
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Allen I could make the bottom turn slightly better by just filling and gas speed would probably go up, but not necessarily cfm the shape needs changing to get a big improvement in flow which is what I'm after. For a given size port getting the shape right gives the highest flow and gas speed. I've got data on various ports at different lifts so can plot flow curves and compare. I'm interested to do a comparison between the increased flow, now up by over 50% to the increased port volume. For valve size a 50% bigger valve would be 60mm, 50% bigger port would be 40mm, which highlights that improving the shape is where gains are best.

The valve to port to flow ratio sizes on the stock head has a valve that can flow virtually half as much again restricted because of mismatch of what it could be if port size and shape was more optimized. Optimizing for the std valve size would require a bigger than stock port and carb which would also optimize gas speed because it would be closer to it's maximum speed because of its more efficient shape. So to get higher speed earlier at lower rpm for a given valve size the valve needs to be smaller as well as the port to give its best. The 42mm valve is up by 1.5mm 3.7% I'd guess the port volume is up possibly 15-20%, (but until I measure that is only a guess) The stock 40.5mm valve should have a carb size around 34.5mm to get optimum flow. But you cannot get the flow volume and speed with out changing the shape and configuration of the port. And the big question is would the gas speed in a 15-20% bigger port be greater at all rpm or only at high rpm? Where would that crossover take place? If it's below 3,000rpm or 2,500rpm it makes virtually no negative impact.

This is minus the bell, with nothing on the port;

.410" - 155.5
.400 - 155.5
(.390 -156.8?)
.350 - 155.5
.300- 154.2
.250 - 142.5
.150 - 93.84

Best of 167 with the bell. Now I'm leaving it alone as its so easy to lose flow and not get it back. Should have some 34mm id tube tomorrow to make manifolds, the tube wall is 3mm so I can port it to 36mm if necessary. I'll make plates to fit to the ports with countersunk screws and bolt manifolds to them and see where we are. They will need to angle out a bit so the carbs can fit.

Last edited by Mark Parker; 09/12/19 3:55 am.

mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #784028 09/12/19 6:36 am
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Very interesting Mark, how are you measuring gas speed over flow?


beerchug
Re: The what if A65 67hp challenge. [Re: Mark Parker] #784031 09/12/19 7:51 am
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If the flow rate and port area are measured, the gas speed can be calculated. Common calculations in HVAC work


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Re: The what if A65 67hp challenge. [Re: Mark Parker] #784039 09/12/19 11:43 am
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Thanks Andy.


beerchug
Re: The what if A65 67hp challenge. [Re: Mark Parker] #784045 09/12/19 12:51 pm
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This may be interesting for Nick, The 76x84 760cc A65 the factory were testing at Umberslade in 1970 was making 79hp @ 7,000 with 62lbft. (better hp than the 750 Commandos, even in '73 when Peter Williams won the IOM with 76hp.) Not only that but it was over 60hp from 5,000, very potent indeed. It looks like the power curve of an F750 three is on the same graph with open mega exhaust and 30mm carbs, it almost has the power of the big A65 but at 8,500, the three was falling away after that and they were testing to 9,600 though it was out of breath.

I've read that the guys working on the A70 were very excited about the potential, and I guess that's why.

The threes were favoured because they were smoother I guess, and they are a fun thing and sound wonderful. I owned one for many years but Ben's 79.5x74 90degree A65 I'm sure is as smooth, and its also much lighter and possibly capable of higher hp . Maybe when it's done some miles and we get it tuned well it might have some dyno time and we'll see how it compares.

Anyway the hp calculator for the Thunderbolt's 167cfm on a 750 race engine predicts 87hp frown at around 8,500-9,000 which would also need testing to see. The 90degree short stroke is more likely to survive and we've had one around 8,500-9000 a few times. Exhaust choice could no doubt move power around the rev range. The hp calculator accounts for 5 states of tune 'race engine' is the 2nd after street/strip.

It's sad money was being spent elsewhere on dubious projects. The 350 isn't one of those but it had hit a wall at 34hp and could make no more without a new head casting.

It's pretty exciting with new books coming out revealing what was being done. And what potential the A70 represented.






Last edited by Mark Parker; 09/12/19 1:46 pm.

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Re: The what if A65 67hp challenge. [Re: Mark Parker] #784097 09/13/19 12:05 am
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The A70 could have achieved a lot of race winning but the only blokes who got the chance
to do anything with it were the yanks. Although there were lots of 'back-door' motors sold at
the time, they could only really be used on 'chairs', they were mostly built out of pilfered parts.
It was a shame it was wasted as a dirt bike but that was the management decision.
No teams really got the chance to use the engine in anything else.

Re: The what if A65 67hp challenge. [Re: Mark Parker] #784104 09/13/19 1:20 am
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You can see what's going on here, Doug H is a triumph man, his option was road race a Bonneville or a Trident. I don't think there was any way in the world he would consider basing a road-race program on the A70, there is rivalry between the two brands. In '70 it's at the same power level as the three but it is not going factory road racing. The R3 is BSA but it's a Triumph based engine so that's fine. The A70 more powerful than the Commando like you say can go in the chairs. And the misinformation begins, it's not really suitable for solos, as Tony Price demonstrated so emphatically in the '80s as totally false.


mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #784118 09/13/19 5:09 am
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Mike 'the-bike' showed 'em how it was done in 1965 at the 'Hutch'. Beat all the triumph team etc.
Beezers never got into the spirit of it though, the blokes at the competition shop would have been great
at preparing them, instead they wasted all that effort trying to win at daytona on a slug. Meanwhile
the uk sidecar championships were dominated by a65's, proving the real power and strength of the motor.
That's despite all the bs about them being fragile.

Mind you, Mr Hailwood could probably have won on a bantam complete with GPO legshields!

Re: The what if A65 67hp challenge. [Re: Mark Parker] #784122 09/13/19 6:26 am
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The slug they were testing at Umberslade was putting out at least the same power per cyl as the best triple. Looks like this particular one had A65 pistons and shorter stroke. Over 56hp at 9,000. 112hp per ltr. The A65 valve gear is very robust, not like the triple's separate boxes that chew out gaskets. I made solid copper ones like the head gasket for my T150V, but the motors are a pain and expensive to work on, complicated, heavy and I was going to say you never know where they are going to leak oil next, but usually the pushrod tubes.

I really think using a stock cam for high rpm in an A65 is the way to go, it's easier on the valve gear and doesn't require high spring pressures.

Allan, the old port is 50cc the new one 58cc 16% increase, (about equivalent to a 31.5mm port) the flow increase is 54.6% so the port speed has to be 38.6% faster for a given vacuum created by the engine, though the engine needs to spin faster to get the vacuum and though it gets complicated, 58cc is not a big port and I doubt any loss down low will be apparent.

I'm trying to think what it will actually do, the vacuum the engine creates will drop with bigger throttle openings because more air rushes in. The throttle slide position determines the amount of air to vacuum but there must be a crossover where the air speed is faster in the wide open bigger port, if both ports flowed the same and one was bigger there would be no cross over and velocity would always stay slower in the bigger port but with these ports there is a point where the velocity becomes faster in the big port compared to the small and the motor being fed more air will want to rev more creating more pull on the intake with exhaust effect and higher piston speed and it may never get to a point or practical rpm low enough to actually have it lose any low rpm hp. Bigger bore exhausts are more likely to create that effect because gas speed there will drop and not pull air through till higher rpm, though exactly when that happens is hard to predict exactly other than the higher speed small intake, the bigger one in this case, should be better than a slow little one (where you don't get)or a slow jumbo size one (where you wait).

It may be, and the 883 is like this, that you do not snap the throttle wide open at low rpm but roll it on, the 883 is massively responsive but the reason for CV carbs is to keep the slide position controlled so that you get no more throttle opening than the engine can use at whatever rpm its at, non-CV carbs rely on the rider to give that control. And using that control you may never get a negative effect, just a more responsive and much more powerful engine. Swapping heads on these things is very easy unless you put the things in a frame that requires removing the engine to remove the head frown as is the RGV because you cannot get the rocker shaft out.


Last edited by Mark Parker; 09/13/19 10:28 am.

mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #784133 09/13/19 11:40 am
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80 HP from a 40 inch 2 valve twin in would be outstanding in 1970 with the port knowledgable of the day.I don't believe the Japanese and Italian OHC engines could not make that at reasonable RPM's with the same displacement for anything close to a street engine..Dyno readings at exteremly high rpm may only be for engineering bragging, car tuners are famous for this...lol...Honda was getting 60 HP from their racing 6 cylinder 250's @ 16000 rpm in the mid 1960's, but the engines barely ran below 6000 rpm. and required the best riders..
Jim Rice's 750 BSA twin was really the last competitve Brit twin in Amercican flat track in the early 70's. The best head porters of the day were CR Axtell and Jerry Branch. CR Axtell 750 Triumphs were rated at about 71 HP, I believe at the crank...This would be for one gear use in flat track wherea wider powerband was required.Certainly the better head of the BSA would make more power...But on longer tracks no Brit twin was competitive with the Harley XR750..I believe the XR made just about 83 HP then and of course the Harley firing order gave better traction on dirt...And Harley did have an excellent factory racing program.
Triumph always seemed more successful overall at land speed and drag racing . Might be because the Triumps were more popular, so cheaper to fix when they blew up, lol and the horrible reputation BSA 650's had in the USA in the later 60's...
But I do think 67 HP from a 650 BSA is reasonable goal....As I have mentioned, my 650 Triumph LSR is the only comphehensive 650 Birt engine dyno information. 55 RWHP on an accurate dyno at 7100 rpm, peak torque of 46 ft lbs at 5100 rpm and still has 40 ft lbs of torque at that 7000 rpm..That might be about 62 HP at the flywheel and I'm using a head reworked by Rob Hall but the engine has very little tuning work beyond the orignal dyno tests...
As always, dyno reports can't be compared unless done on the same device...


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Re: The what if A65 67hp challenge. [Re: Mark Parker] #784139 09/13/19 12:18 pm
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The tumble on 4 valve engines is an attempt to add back in the swirl lost in the move from 2 to 4 valves, so there is not much to gain from adding tumble to a 2 valve when you naturally have swirl. Swirl gives you the low down power, 4 valves give you better power at lower revs but no swirl so early ones are gutless at low revs hence the need to put tumble in so you get the lower revs power back. A simple way to get it back is to have 2 different head diameters on the inlet valves, so the incoming flow gets a bias from one side and starts the tumble.

Re: The what if A65 67hp challenge. [Re: Mark Parker] #784145 09/13/19 12:50 pm
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Originally Posted by kommando
The tumble on 4 valve engines is an attempt to add back in the swirl lost in the move from 2 to 4 valves, so there is not much to gain from adding tumble to a 2 valve when you naturally have swirl. Swirl gives you the low down power, 4 valves give you better power at lower revs but no swirl so early ones are gutless at low revs hence the need to put tumble in so you get the lower revs power back. A simple way to get it back is to have 2 different head diameters on the inlet valves, so the incoming flow gets a bias from one side and starts the tumble.

Not all two valve engines have adequate swirl...Obvious example is a vintage Triumph...The 79 750 parallel port head added some port velocity and turbulence or swirl...When I closed up the piston to head squish on my 79 T140D to .032, the engine now runs without detonation on 90 R+M/2 octane fuel with a measured 9.2 compression ratio.The faster combustion burn also allowed me to back off the timing to 35 degrees.I built my Triumph 650 with this theory using flatter top pistons with less compression (10.5-1) and less cam timing and high velocity ports..Adding swirl is also a trick used my tuners of older US OHV V-8 engines to use higher compression on pump gas.. But I am no expert on this other than what I have done to a few Triumphs...


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Re: The what if A65 67hp challenge. [Re: Mark Parker] #784156 09/13/19 1:58 pm
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Hillbilly the 79hp A65 was a 760 with 84mm stroke. The hp calculator predicts over 80hp for a 650 but it would be at a zillion rpms. I think this was the A70 being developed. I also think the flattrack guys speak in rwhp. To convert, Peter Williams Commando was 76 at the crank 67rwhp, F750 Triples 73rwhp 84at the crank, our twins probably have similar losses in that sort of proportion.

That's interesting Commando, why the Chrysler hemi's are so impressive. They are selling 700hp versions in Cherokees here now, 470hp did seem adequate when I used to test-drive them. Highway patrol have a Hemi 300 here now and from what I hear they love it. They have other fast cars but the 2v hemi's different. It might also explain why the hemi was so successful in drag racing. Another plus for a two valver. It might not be the optimum for Moto GP but for the street it can be punchy and joyful to ride.


mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #784157 09/13/19 2:11 pm
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"The 42mm valve is up by 1.5mm 3.7%" in diameter maybe

When I work out the areas I get 1287.6 mm square for the 40.5 mm valve


1384.7 for the 42
difference 97 mm square and change .

(97 / 1287.6 ) x 100 gives 7.5 % increase in valve area.


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Re: The what if A65 67hp challenge. [Re: Mark Parker] #784165 09/13/19 3:40 pm
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Gavin, he is talking flow area (circumference * lift) so it is a ratio of diameters (42 / 40.5 - 1.037 or 3.7% increase).

Re: The what if A65 67hp challenge. [Re: Mark Parker] #784168 09/13/19 3:57 pm
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Ah, OK then.


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Re: The what if A65 67hp challenge. [Re: Mark Parker] #784170 09/13/19 4:03 pm
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The Hemi success in drag racing was in supercharged gas and fuel classes. In N/A gas classes it had no advantage over properly prepped wedge heads..The world's fastest piston engine wheel driven car at Bonneville in unlimited streamliner calss, 462 mph .is powered by a highly modified turbocharged Chevy V-8 2 valve wedge head..Two valves can make power, yes...


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: The what if A65 67hp challenge. [Re: Mark Parker] #784212 09/14/19 12:09 am
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It's a shame i didn't buy the a70 crank i was offered back in the uk years ago but i had embarked on the offset norton route.
Still, i think this motor should be pretty good with an a10 one, if we keep revs under control, i've got a limiter set up for it.

When i referred to the slug, i was talking about an a50 taking on a triumph 500, a very costly exercise in terms of development.
All for a single race........ They had a race winning motor already, they just didn't let the guys who knew about it take it further.
The politics and why's and wherefores of large companies are seldom straightforward but the science of 2 v's 4 v's 6 valve heads etc
is played out today and 4 valve designs are hard to beat as far as efficiency etc are concerned. Like comparing fuel injection with
carburettors, no-one's going to go back to carbs now just like using domed pistons and hemi heads, they've had their day and been
bettered. Chrysler have to use bloody great engines to achieve little gain over comparable 4 valve makers at the cost of fuel, size etc.
They also have a stinking name for reliability, certainly up here.

Re: The what if A65 67hp challenge. [Re: Mark Parker] #784230 09/14/19 2:47 am
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Originally Posted by Mark Parker
I've read that the guys working on the A70 were very excited about the potential, and I guess that's why.

<snip>

It's pretty exciting with new books coming out revealing what was being done. And what potential the A70 represented.

That's quite interesting info, Mark.

What book(s) did you read that in? I'd like to get a copy.

Re: The what if A65 67hp challenge. [Re: Mark Parker] #784240 09/14/19 9:31 am
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Forthcoming books. I received a message on facebook from the author, he said; I write for the motorcycle comics but I'm also putting 2 books together (one on the road bikes one on the racers) on the A65/50. He said he's talked to 80+ factory guys including loads to Peter Brown who did most of the A65 development work. He has all his dyno printouts as well as the original drawings for the Spitfire MKIV head which were much more accurate that earlier versions. He shared some graphs with me.

I am certainly looking forward to these. They sound absolutely fabulous. I think they go broader than just the factory period. And will likely feature stuff about bikes such as Tony Price's A65 750 in the Norton frame that was so dominant in classic racing in the '80s. I don't know how much I should share, but this is relevant to this post and it may help promote the books a little. He said, "A guy here - Tony Price - did a lot of work with oval ports on A65s which might be of interest..." Which really explains a lot.

"When i referred to the slug, I was talking about an A50 taking on a triumph 500" Nick, I knew what you were talking about, but the dyno graph of the short stroke A50 with A65 pistons seems very promising. Over 56hp @ 9,000rpm. But really the A65/A70 or A65 big bore 750 would have been the thing to be developing and promoting, by putting them on pavement tracks like Daytona. They could have easily challenged the triples and given the twins kudos for the prospective buyers of the whole twin range. The A70 is very interesting, it's built as the basis of a real hotrod, I don't know what power they had as sold. But we will probably find out. However in 1970 the lighter twin was being tested equaling the triple's hp. Had they had the oval ports at that stage someone might have said why are we racing this and not that?


mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #784245 09/14/19 11:25 am
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I'll have to buy those when they come out.

Re: The what if A65 67hp challenge. [Re: Mark Parker] #784251 09/14/19 1:36 pm
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The A50/65/70 engine had the making of a great engine but was let down by some poor design.
The timing side bush was too small, a bigger bush or a ball race would have been an asset to reliable performance
The oil pump was inadequate, the bottom end would have been more reliable if the oil pressure stayed in double figures at idle
The only oil filtration is a sludge trap in the crank which needs a complete engine strip to clean
Gearbox ratios were horrible, it should have been fitted with a 5 speed
A centre crank bearing and balance shaft would have reduced the filling loosening vibration


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Re: The what if A65 67hp challenge. [Re: Mark Parker] #784257 09/14/19 2:32 pm
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Streamliner engine, highly modified as in twin turbos with sewer size pipes and heads machined from solid. With 50-60 lbs of boost you do not need four valves to get the air in.
Centre bearing crank with 90 degree throws and roller/ball/needle bearings can be incorporated in the current design with modifications. I made a spur gear drive gerotor pump and five speeds are available. It seems the biggest items left are a cylinder/head with through studs to the case and proper ports.

Re: The what if A65 67hp challenge. [Re: DMadigan] #784259 09/14/19 3:04 pm
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Originally Posted by DMadigan
Streamliner engine, highly modified as in twin turbos with sewer size pipes and heads machined from solid. With 50-60 lbs of boost you do not need four valves to get the air in.
.

Modified yes as in 2200 plus HP from 380 cubic inches with 65 pounds of boost at 9000 rpm.He chose a LS Chevy OHV V8... It's not easy to get that power, a lot of tuning and engineering . But there are other engines can can make that power including 4 valve smaller displacement engines..


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: The what if A65 67hp challenge. [Re: DMadigan] #784268 09/14/19 5:06 pm
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Originally Posted by DMadigan
Streamliner engine, highly modified as in twin turbos with sewer size pipes and heads machined from solid. With 50-60 lbs of boost you do not need four valves to get the air in.
Centre bearing crank with 90 degree throws and roller/ball/needle bearings can be incorporated in the current design with modifications. I made a spur gear drive gerotor pump and five speeds are available. It seems the biggest items left are a cylinder/head with through studs to the case and proper ports.


The need for through studs would not arise if barrels were cast from aluminium.
Aluminium is strong in tension, in fact it is strong loaded in any direction unlike cast iron which can only be safely loaded in compression


BSA B31 500 "Stargazer"
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Greeves 350
Greeves 360
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Jawa 500 "Llareggub"
Aprilia RSV Mille "Lo Stregone"
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Re: The what if A65 67hp challenge. [Re: Mark Parker] #784291 09/14/19 10:08 pm
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It seems the major factor in performance came from the cylinder head, Peter shared this with me and it highlights what would have been possible had BSA developed the A65 for F750.

"Tony Price was a bit of a phenomena. People would flock to see him at Mallory Park on his Norton framed A65 as he used to go flat out into Garrards. NO ONE does that and in the late ‘80s his lap times would have qualified him for the Transatlantic races in among Schwantz and Merkel. No kidding this guy was seriously fast !! Of interest to you was the fact that he also did oval inlet ports, to get round the breaking through issue." Tony did this with a 4speed.


mark
Re: The what if A65 67hp challenge. [Re: DMadigan] #784307 09/15/19 1:11 am
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Originally Posted by DMadigan

Centre bearing crank with 90 degree throws and roller/ball/needle bearings can be incorporated in the current design with modifications. I made a spur gear drive gerotor pump and five speeds are available. It seems the biggest items left are a cylinder/head with through studs to the case and proper ports.


The oil pump you came up with was great, for a standard bush arrangement motor it was a huge plus but the lack of interest shown was
a shame. With a modified relief valve setup it would be well worth fitting. With an end fed motor the benefit would be less as the oil delivery
required is reduced by at least 40% so the relief capability would need to be significantly larger.
Through bolting is a good strengthening move too, the devimead kits had a much larger base flange arrangement to add strength but bolts
down into the case are better albeit more difficult to do. Centre bearing crank would be better for high rpm use and noting Mark's flow
figures, increased rpm is where the largest power gains are. The cost of this may be a limiting factor though, just manufacturing a crank from
scratch would be around 60-75% the value of a typical road bike a65. Maybe when they have become as rare and sought after as a vinnie, it
may be worth while.

Re: The what if A65 67hp challenge. [Re: Mark Parker] #784328 09/15/19 5:43 am
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Building a centre bearing 90 degree throw crank from scratch is a bit expensive but cheap the way I did it using XS650 crank parts. It would be fairly cheap making the XS crank parts from scratch since only the end webs have a lot of material removed. The inner two are basically round slugs with a few holes in them. Plus it would be easy to change stroke. Rods, pins and bearings are really cheap for CR500s and they are steel with needle bearings that even the stock A65 oil pump could easily supply.
I made knock-off wheel spuds out of 4340 steel to put Halibrand magnesium wheels on a Corvett and the cost was around $200 each so the crank parts would be in the same range.
There is always the gap between what people want and willing to pay for.

Re: The what if A65 67hp challenge. [Re: Mark Parker] #784329 09/15/19 6:13 am
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Sorting out the centre bearing arrangement must be quite difficult but not having seen how you've done it i reserve judgement.
I wouldn't place a lot of faith in the XS650 crank personally as i saw so many xs650 motors go bang with quite horrible results.
If you thought a65's blow up well, you should see one of those go bang, they disintegrate.
I understand that it was one of the areas that yamaha spent a lot of time and money on. Welding the centres etc. certainly on
their race motors. Starting from scratch with the crank may be a better move, but i don't know.
The Cr500 rods, what are their centres? Certainly a good option if they fit the bill and are reasonably priced. One of the big advantages
of needle big ends is their oiling, or little need for it.

You'll have to get that thing running at some stage David, i know you have nothing else to do eh?

Re: The what if A65 67hp challenge. [Re: Mark Parker] #784343 09/15/19 3:49 pm
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I know, too many marshmallows in the fire. I heard most pressed together cranks were welded for racing but I doubt this crank modification would be acceptable in any class. I do not know if any engines had speed limiters back then, I think it was more rider feeling the acceleration drop off and shifting up.
CR500 rods are 144mm which is better than the XS rods at 130mm. Those I would have to take about 19mm off the cylinder to get any compression.
The intermediate plate holds the circlipped ball bearing so no need for crank thrust washers. These are still the XS rods:
[Linked Image from live.staticflickr.com]
I sourced a set of 1mm over XS pistons so I can put it together with the stock cylinder and head. I really want to make a new cylinder/head with the various improvements that I talked about and Mark's ideas about porting.
[Linked Image from live.staticflickr.com]
I found a foundry in LA that will work with me on casting clutch housings for the triples so actually doing this is a possibility. Castings are about $16/lb plus the match plate. I can make the masters.

Re: The what if A65 67hp challenge. [Re: Andy Higham] #784454 09/16/19 9:19 am
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Quote
The need for through studs would not arise if barrels were cast from aluminium.
Aluminium is strong in tension, in fact it is strong loaded in any direction unlike cast iron which can only be safely loaded in compression

Yes it is stronger in tension that cast-iron, but cast iron does not creep like aluminium does so through bolts would still be needed or a steel head gasket as done with the all alloy RR V 8's .
Otherwise the head will end up like a crinkle cut chip in very short order.
Plus you will need more bolts

Last edited by BSA_WM20; 09/16/19 9:20 am.

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Re: The what if A65 67hp challenge. [Re: Mark Parker] #784462 09/16/19 11:48 am
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Built up engines ,separate cylinders and crankcases are not an ideal design, a once piece block and cylinder is stronger...That being said, I believe modern engines still using separate cylinders all use through studs..Of course through studs are only as good as what they are screwed into...Pushrod Tom from this site runs a turbosupercharged 650 BSA in land speed racing..The bike has turned impressive speeds,likely around 100 hp ,wide open for 1-1/2 miles..He has broken engines but I can't say it's from the lack of through bolts.I don't know if he uses aluminum cylinders..


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: The what if A65 67hp challenge. [Re: Hillbilly bike] #784463 09/16/19 12:02 pm
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The 3 modern(ish) bikes in my workshop
Aprilia RSV has separate barrels with through studs
Kawasaki ZZR1400 has one piece top crankcase and barrels
GM500 has separate barrel bolted top and bottom


BSA B31 500 "Stargazer"
Greeves 200 "Blue Meanie"
Greeves 350
Greeves 360
Suzuki GSX1100 EFE "Sorcerers Apprentice"
GM500 sprint/LSR bike "Deofol"
Jawa 500 "Llareggub"
Aprilia RSV Mille "Lo Stregone"
'35 & '36 OK Supreme
Kawasaki ZZR1400 "Kuro no senshi"
Re: The what if A65 67hp challenge. [Re: Andy Higham] #784464 09/16/19 1:02 pm
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Originally Posted by Andy Higham
The 3 modern(ish) bikes in my workshop
Aprilia RSV has separate barrels with through studs
Kawasaki ZZR1400 has one piece top crankcase and barrels
GM500 has separate barrel bolted top and bottom

The GM500 is purpose built "racing" engine?


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: The what if A65 67hp challenge. [Re: Mark Parker] #784475 09/16/19 2:43 pm
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I think Tom may use alloy cyls.

These are mine. I originally used 8mm stepped studs and bolts and they were good for years until I did the oval ports, then the head gasket would seep oil and studs started pulling out. So I used fully threaded head bolts stepped to 9mm where they screw into the cyl. The rear two I use 10mm with the bolt heads still on. SRM/Devimead kits run imperial stepped studs similar size to 8mm into the block. The reason is because the bolts are very close to the bores and can distort them, why sleeving a std block is unsuccessful. Through bolting eliminates the distortion. I have the studs 35+mm into the cyl. I can see slight distortion right near the top with the 9mm but it doesn't smoke. 9mm is very solid when torqueing, feels quite different to the 8mm.

[Linked Image from i.postimg.cc]

I use bearing blue and wet and dry to get an exact match between cyl and head so I get a good gasket seal. I used my worst most ratty cylinder head for the big oval port experiment, I actually lifted the guide about 4mm building up the valve spring seat area. Lots of JBweld in this it's around 200cfm @ .410 valve lift, a bit more at higher lifts that I see no point in using. On a 750 Wallace racings hp calculator for a race engine estimates 103hp somewhere between 10,000-11,500rpm. The 883 is still making power near 8,000 where the graph would start falling I was not game to find out. I can get around 180-190cfm without lifting the guide and without breaking through if I am careful enough. Ben's 750 is around 190cfm with the potential of 90-98hp @ 9,500rpm or so, the difference between a strip/street and race engine. Ben's engine has 10-1 compression the 883 11-1.

[Linked Image from i.postimg.cc]

So unless you intend to build an engine to exceed that sort of rpm the stock cyl head casting is more than adequate. I wouldn't want to spin a stock configuration crank that high, the dynamic load on a 90degree is around 45% less, so using my logic, which is often questionable, it's like being 45% stronger than std. An A50 will run over 9,000 so the valve gear is quite capable, and it's easier on everything to use the 473 cam than something more radical. This is our modified cut in half crank. Not that I particularly want to be in a dyno room with Bens 750 over 9,000. His bike is so smooth and sweet, with excellent bottom end and midrange.

[Linked Image from i.postimg.cc]


Last edited by Mark Parker; 09/16/19 2:47 pm.

mark
Re: The what if A65 67hp challenge. [Re: Andy Higham] #784500 09/16/19 7:11 pm
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Originally Posted by Andy Higham
The 3 modern(ish) bikes in my workshop
Aprilia RSV has separate barrels with through studs
Kawasaki ZZR1400 has one piece top crankcase and barrels
GM500 has separate barrel bolted top and bottom


Yes it's a 500cc 4 valve single, just under 90bhp @ 11,500rpm.


BSA B31 500 "Stargazer"
Greeves 200 "Blue Meanie"
Greeves 350
Greeves 360
Suzuki GSX1100 EFE "Sorcerers Apprentice"
GM500 sprint/LSR bike "Deofol"
Jawa 500 "Llareggub"
Aprilia RSV Mille "Lo Stregone"
'35 & '36 OK Supreme
Kawasaki ZZR1400 "Kuro no senshi"
Re: The what if A65 67hp challenge. [Re: Mark Parker] #784516 09/16/19 8:55 pm
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So, the cases don't actually end up wider Dave, that's nice, how do you get on welding that plate into
40 year old sand cast alley without it ending up like a banana?

Brian Hart turbo motors were a one piece arrangement done on a 'budget', that man was bloody clever.
I'm talking integral cylinder head etc.

Re: The what if A65 67hp challenge. [Re: Mark Parker] #784518 09/16/19 10:17 pm
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Not welded. You could not get the crank in if the plate were welded to either side. I machined away enough of the drive case to sandwich it in between the two halves. All the case bolts except the one bridging the tunnel go through it. The plate is bolted around the centre ball bearing then the crank and plate put into the case. Roller bearing on the drive and needle bearing on the timing side.
As Mark found, the studs are too close to the bores to put in 80mm pistons with realistic size studs which is why I want to make a new cylinder/head with 3/8" studs. At the same time run the outer four studs from the case to the head.

Re: The what if A65 67hp challenge. [Re: Mark Parker] #784521 09/16/19 11:44 pm
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Dave,that's quite interesting ...I like adapting exisitng parts..


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Re: The what if A65 67hp challenge. [Re: Mark Parker] #784529 09/17/19 1:49 am
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Dave, Peter Turner moved the outer studs in his cyl so he could use bigger pistons 82mm at least. His motor is 914cc or something like that. Maybe you could get a cyl from him they look fabulous. 9mm works well in the alloy block and though through bolting would be preferable it's not necessary. I made my cyls to be strong, though the base flange bolt location means cutting in for flats for nuts, I used flange nuts that suit a 12mm spanner to minimize that cutting.

Peter uses roller rockers in that new section, they give 1/2" valve lift from the stock cam. It's a very crisp sounding motor.

[Linked Image from i.postimg.cc]


mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #784543 09/17/19 3:51 am
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Amazing work on that motor, the rocker box lift alone. Braw.!


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Re: The what if A65 67hp challenge. [Re: Mark Parker] #784545 09/17/19 4:20 am
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Looks like a Cylon BSA laughing

Re: The what if A65 67hp challenge. [Re: Mark Parker] #784546 09/17/19 5:28 am
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Gavin, is this the type of carb you bought? PKW $60au for a pair including postage?

If I get 34mm I can use them on the Firebird with either head.

[Linked Image from i.postimg.cc]


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Re: The what if A65 67hp challenge. [Re: Mark Parker] #784549 09/17/19 6:20 am
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If a new head is cast, besides making the chamber for the 80mm pistons, the valves could have buckets added so smaller stems can be used without the rocker side load causing problems. That would reduce guide and stem wear too. I would have to go back a ways to find a two valve head with buckets large enough for the springs, around the beginning of the four valve era.
Supertech has buckets up to 37.5mm diameter for BMW S14, 35mm for VW 16V.

Re: The what if A65 67hp challenge. [Re: Mark Parker] #784557 09/17/19 7:48 am
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Yes, of course you wouldn't be able to weld that centre plate, DURRRRRRR.
As well as the fact you couldn't get the crank in it wouldn't be able to leak oil would it????? Bloody shame, it would loose it's character.

The largest i ran was with 80.5mm pistons and 90mm crank. Around 920cc. (Similar to the Hanks' type setup.)
I did this as i lost a circlip and screwed one bore running 79.5. Normal was 79.5 or 80 x 89 (buttons after that!)
The shaped/stepped 3/8- 5/16 studs were ok using grade 10 just long and set in well. No head gasket problems really.
BUT, that barrel was really good close grained cast iron.
Used my own long 3/8 UNF/UNC barrel studs as far into the cases as they would go, grade 10.
I did have a through bolted barrel off an a65, as it was bored to +100 (T140+0.60 pistons) We just made tubular sleeves that
Screwed into the top 4 or 5 fins then ran half a dozen 5/16 allen bolts down into the base flange from the sleeves. It was OK but
the triumph pistons were not very good even after machining a fair bit, the basic shape wasn't really correct for the beezer head.
I ended up having the barrel lined and it was sold with the bike on the 650 spare engine. Getting the angle right for the drilling was
the thing, considering we did it on a pillar drill! It gave us an 840cc or so motor, and after shaving around 80 or so thou off the
barrel it was OK. A bit over 10-1 as i remember.

I never saw that big beezer of peter turner's at a track, was it any good?

Re: The what if A65 67hp challenge. [Re: Mark Parker] #784568 09/17/19 11:05 am
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That looks identical, jets are Keihin types. I have numbers somewhere


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Re: The what if A65 67hp challenge. [Re: Mark Parker] #784572 09/17/19 11:53 am
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It's his road bike Nick. He's even fitted an electric start. He works in motor sport so has flow bench and obvious skills. The carbs are 36mm from memory. He welded up a std crank and had it ground to 85.5mm?

I cannot use a flange plate on the port on the Thunderbolt to mount a manifold so welded up the bolt holes added some weld and drilled and tapped new mounting holes and made a manifold. I need a mill to do the gasket face frown It's pretty close with a file but a mill would be so easy.

I'm guessing the carbs suit 2 or 4 stoke motors.


mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #784573 09/17/19 12:00 pm
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Crikey! All this talk of giant motors makes my 650's seem like Bantams. I have enough trouble keeping everything buttoned down as it is. I have been using the John Hill barrels for a few years with good results. Using 5/16 bolts I have to be careful with the torque wrench though. I go about 26 ft/lbs and they stay tight with barely noticeable distortion in the bore. The turbo is undergoing a refit. The right cyl. gets hot and stresses everything. The left is ok. This has been an ongoing problem so if we can get 'er together we will have to measure each cyl to try and find n fix the problem. This spring we did at least 30 full power pulls at well north of 100 rwhp and it behaved perfectly. Of course a 3 second dyno pull is not the same as a mile or more at Maine!
As a side note, the original motor lasted for years with much abuse. The original 1966 5/16 studs and nut were never a problem. However, the motor we used for nitrous only use detonated and blew all of the 'special grade 8 nuts' right off the studs. Nuts were soft. Cylinder came up and hit the tank creating quite a leak. Very lucky. No flame! The adventure continues. I'm enjoying this thread! PRT

Re: The what if A65 67hp challenge. [Re: Mark Parker] #784579 09/17/19 1:10 pm
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8mm and 5/16 are the same size. By using metric threads I was able to simply tap to 9mm when I needed to, being the same pitch. 3/8 is 9.4mm.

Has Peter Crawford talked to you about his books on A65s Tom? Do you have power graphs you could share?


mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #784588 09/17/19 2:55 pm
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The carbs came with un numbered big jets, i think they are mostly aimed at twostrokes. i still havent tried mine yet.


71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
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Re: The what if A65 67hp challenge. [Re: Mark Parker] #784629 09/17/19 10:49 pm
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Originally Posted by Mark Parker
It's his road bike Nick. He's even fitted an electric start. He works in motor sport so has flow bench and obvious skills. The carbs are 36mm from memory. He welded up a std crank and had it ground to 85.5mm?

I cannot use a flange plate on the port on the Thunderbolt to mount a manifold so welded up the bolt holes added some weld and drilled and tapped new mounting holes and made a manifold. I need a mill to do the gasket face frown It's pretty close with a file but a mill would be so easy.

I'm guessing the carbs suit 2 or 4 stoke motors.


Ah, shame i thought that beezer may be used properly. It does look pretty though.
The first couple of heads we did used bolt on manifolds done in a similar fashion to the way you describe.
You have to cut off the whole back of the head really for a good job, it makes the welding easier even with
stubbs.
Those wing wong carbs look very good, and similar to the JRC type i think. (PWK, Kehin etc etc.)
You can buy jet kits for them, i suggest starting at around 135 as a main on your 750.

I still don't know about all this huge carb lark though, i suppose that at a squillion revs you may need bloody
great orifices to get a mixture in but on a typical race track you are flat out for only a short while, the ability
to accelerate quickly from 4-7k is far more important and gets better lap times than another 2mph on a straight.
I have a set of 36mm venturis here for my old weber but i only ever used them once or twice, 33-34 was the norm.
If i raced over on the iom then 36 may have been the way to go. In my experience, many racers tried huge carbs
and went back to smaller ones for the same reason, lower and mid-range.

No i have no records of any stuff i did on the dyno as it was nearly all back in the uk.
All binned when we moved here in '99. Most of it was on a 750 srm kit and the early 89x76 rig. There wasn't much
but i remember the big jump when we tested the 810cc motor, straight away we got upper 60's at the back wheel.
We struggled to get better than mid 60's with the 750 kit.
The last time we tried it (over here) we were getting the 80+ we had been chasing for a long time, but the only things
i got to ride against were bloody hondas.

Last edited by NickL; 09/17/19 10:51 pm.
Re: The what if A65 67hp challenge. [Re: Mark Parker] #784637 09/18/19 12:12 am
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But, big carb and big port doesn't mean big flow 34-36 just means the carb will match the valve size, and the ports themselves are not huge but the flow is. I have this manifold 34mm, when the carbs arrive, slow boat from China, we'll see what the whole deal flows. The Thunderbolt head is better than the Lightning at this stage, and I put the guides back in the Lightning so will not mess with it anymore it has plenty of flow for a 650. I have some more twin carb heads I can mess with.


mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #784668 09/18/19 11:11 am
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Mark, Not aware of Peter Crawford. Most all of the test results are in Mikes computer.

Re: The what if A65 67hp challenge. [Re: Mark Parker] #784672 09/18/19 12:09 pm
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When comparing dyno readouts we all need to keep a few things in mind, Primarily,all almost use a Dynojet inertia Dyno, a good tuning machine but the power figures are about 10% higher than the eddy current or water dynos used by the manufacturers...An inertia measures how fast the vehicle drive wheel accelerates the dyno roller..An bike with a light flywheel will show more HP despite it really does not make more HP. Eddy current applies resistence to the dyno roller and can hold the engine from reving to full rpm.
A good example is this partial reading from my 650 Triumph race bike....The dyno is a Superflow , that is both eddy current and inertia..Through years of testing the machine's computer is programmed to show both readings...
The first two columns are Dynojet HP and torque, the second two columns are true HP and torque like the manufactuers use...A/F was disconnected.....Notice the power difference...My bike ran 133 MPH with less than 50 true HP at the rear wheel...

[Linked Image from live.staticflickr.com]


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: The what if A65 67hp challenge. [Re: Mark Parker] #784690 09/18/19 3:40 pm
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This is the graph of the 883. The operator went to some pains to explain it's a ramp type dyno not inertia, he could adjust it to take longer to spin up the drum. It held the bike at a predetermined speed until the run was initiated when it hit the maximum speed or rpm we selected it again held it to that rpm. Except the first run, which indicated 85.4 on the screen with an inaccurate rpm count, so we ended up using speed rather than rpm to control rpm.

The graph is in KW frown even though hp was what was on the screen while we were doing it. 61.4kw is 82.3rwhp which realistically converts to 93.3hp at the crank, 50kw is 67rwhp-76hp @ crank. 40kw is 53rwhp -60hp. If I didn't have to pay to fix it if something broke I'd take it back in and try it with the correct mixture, the new freer flowing mufflers and maybe the extra 1000rpm the operator wanted to run it to. Why I envy the guys developing stuff at Umberslades where they were being paid to test engines and chase the best settings and find exactly what a configuration would deliver, without having to walk home if it all went wrong.

[Linked Image from i.postimg.cc]


mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #784693 09/18/19 4:38 pm
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I believe a ramp rate has a braking device to allow a a pre set rate of acceleration of the roller...An Eddy current is like a generator load device of sorts can can be programed to actually stall the engine at a given rpm...So the power readings having nothing to do with accelerating roller speeds...This is not to belittle anyones tuning , but to clarify why dyno readings can't be compared unless on the same machine..

This is a good example of a water or eddy current dyno...An 830 HP V8 is stalled by the dyno ..





79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: The what if A65 67hp challenge. [Re: Mark Parker] #784729 09/18/19 11:43 pm
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PES are selling 44.5 mm B44 inlet valves , i have just bought a pair, nice waisted heads and are roughly 2mm longer than a stock 71 valve i have lying around, should do the trick without having to sink the seat to prevent coil bind, has the same looking wee collet grooves too.,
I found them on that place,


71 Devimead, John Hill, John Holmes A65 750
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The poster formerly known as Pod
Re: The what if A65 67hp challenge. [Re: Mark Parker] #784753 09/19/19 7:17 am
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Is spring pressure effected Gavin with the stems being longer?


beerchug
Re: The what if A65 67hp challenge. [Re: Mark Parker] #784758 09/19/19 8:59 am
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Bigger valve heads sit further into the chamber, need longer stems to keep spring pressure equal. Or the seats need cut deeper.
I had to get seats cut deeper with the last set of big inlets from SRM, these PES types look more like the thing.


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56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
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Re: The what if A65 67hp challenge. [Re: Mark Parker] #784761 09/19/19 10:34 am
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I was in a discussion with several successful engine builders, auto drag racers....They claim from experience that if you have heads with identical flows rates, but one has higher velocity ports,when cammed and tuned for best power, the lower velocity ports will make more high end power and the vehicle will be faster on the track...


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: The what if A65 67hp challenge. [Re: gavin eisler] #784767 09/19/19 12:01 pm
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Originally Posted by gavin eisler
PES are selling 44.5 mm B44 inlet valves , i have just bought a pair, nice waisted heads and are roughly 2mm longer than a stock 71 valve i have lying around, should do the trick without having to sink the seat to prevent coil bind, has the same looking wee collet grooves too.,
I found them on that place,


Beware of piston contact, although you may get away with them with a standard cam.
You can always use shims under the spring cups to set the weight, had to do that with W+S springs anyway.
Used B50 exhaust valves at one time but they didn't do much good for me, and made cam timing more awkward.
I still reckon the PM +1.5mm inlets are a good valve. (Black diamond) Good shape, weight, length etc.

Re: The what if A65 67hp challenge. [Re: Mark Parker] #784768 09/19/19 12:11 pm
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That actually sounds backwards? If the port is low velocity power has to come in later with a narrower power range? I guess it may depend on exactly what that velocity is. From what I've read the BSA ports are low velocity in as much as the velocity can be increased without approaching any detrimental critical speed. Anyway we will find out, just trying to lace wheels for the '70 Firebird, does anyone know if the front has an offset or if the rim is just central to the forks and axle? The thing weighs a ton.

What I'm after with this head is a nice wide power range, so I'm chasing the best flow from the smallest ports to obtain this.


mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #784773 09/19/19 1:23 pm
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Yes ,perhaps backwards other than extreme drag racing.....I believe you would enjoy this this thread and the especialy the forum in general.... You may have to join the forum to see it. There a lot of pro US and Australian tuners, mostly cars but there are also some bike guys...A lot of it is beyond my knowledge level..

Speed Talk


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: The what if A65 67hp challenge. [Re: Hillbilly bike] #784776 09/19/19 1:35 pm
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Originally Posted by Hillbilly bike
I was in a discussion with several successful engine builders, auto drag racers....They claim from experience that if you have heads with identical flows rates, but one has higher velocity ports,when cammed and tuned for best power, the lower velocity ports will make more high end power and the vehicle will be faster on the track...



Are they using turbos, super chargers or other means which mean the gas/air velocity is not controlled or over come by an external mean.


beerchug
Re: The what if A65 67hp challenge. [Re: Allan Gill] #784781 09/19/19 2:20 pm
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Originally Posted by Allan Gill
Originally Posted by Hillbilly bike
I was in a discussion with several successful engine builders, auto drag racers....They claim from experience that if you have heads with identical flows rates, but one has higher velocity ports,when cammed and tuned for best power, the lower velocity ports will make more high end power and the vehicle will be faster on the track...



Are they using turbos, super chargers or other means which mean the gas/air velocity is not controlled or over come by an external mean.

N/A ohv...


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: The what if A65 67hp challenge. [Re: Mark Parker] #784787 09/19/19 4:09 pm
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Thanks for the advice Nick, it was touch and not go with the last set until the seats were cut deeper, might lose some weight off the piston and gain a little clearance.


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The poster formerly known as Pod
Re: The what if A65 67hp challenge. [Re: Mark Parker] #784820 09/20/19 2:01 am
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Gavin the 44.5mm valves when the port is good flow 200cfm the 42mm MAP valve is similar to the P&M, both are excellent, you could possibly have new valve seats fitted to the big valve head you have. Flow through the MAP 42mm valve is now showing 168.6cfm at stock valve lift with manifold and bell. 160 with just the manifold, which is 34mm. This is the Thunderbolt head frown

If the head could be welded down in the pushrod tunnel and built up, the port could then be widened by 5mm or so more to good effect. I'm pretty sure this could be done without interfering with the pushrods. A MIG may get in there better than a TIG and a welding guru (not me) could probably do it easy. The blue arrow points at the curve in the casting that is the port outer wall. The redarrow is the hole for the guide. In the yellow circle is the alloy plate I JBwelded on. If there is no plate over the break through hole the JBweld can/will crack. This is not a good place to have JBweld as the softer material on the inner wall always results in a bump because it sands away easier than the alloy. It doesn't matter on the floor of the port because its all JBweld.

[Linked Image from i.postimg.cc]

Another view of the plate JBwelded on, this gives no problem in use.

[Linked Image from i.postimg.cc]

Views of the head:

[Linked Image from i.postimg.cc]

Possibly more suitable for a 750.

[Linked Image from i.postimg.cc]

Flow with the 34mm flatslides will be measured when they get here. The big challenge is getting the other side the same. Plus I'm not sure how wide these carbs are I can extend the manifolds a little if necessary and get the carbs further apart, I wanted to keep the port and manifold as straight as possible so the turn at the manifold head area is ok.

Last edited by Mark Parker; 09/20/19 2:05 am.

mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #784824 09/20/19 4:51 am
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Im super interested in this

My numbers are very different from yours.


Full time classic motorcycle mechanic and enthusiast to a fault
Re: The what if A65 67hp challenge. [Re: Mark Parker] #784826 09/20/19 5:44 am
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Mark, Have you thought about fairing in the guide, particularly the down stream side? A cylinder produces an oscillating wake which might be making a wider affected area than the width of the guide. Also, the thrust in the guide is fore/aft so the sides of the guide can be tapered from the roof down to the end.

Re: The what if A65 67hp challenge. [Re: Mark Parker] #784827 09/20/19 6:03 am
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I did put the guide in the lathe and blend the end of it so is hasn't a squared off end. I could try taking a bit off the sides of one and see what it does. But welding in the pushrod tunnel I think might be the place to make big gains. It's already a bit past what a 650 could use, or what might be necessary for the 67hp. I made this guide a push fit so I can push it in and out easily. I've tried fairing before and after the guide its just that if the fairing isn't exactly right and air goes across it, I had that with one side of a head and it took ages to find what was messing one port up. Maybe I could do a better profiled flair. But I'm not messing with this port anymore unless to test the profiled guide.


mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #784848 09/20/19 2:37 pm
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Now I'm not a real expert on engine design, but here are a few of my thoughts. I think we have to look at the history of the motorcycle to understand why the motors were made the way they were. The 90 degree (included valve angle) hemi-head made sense because they could use larger valves than they could with a flatter combustion chamber. Furthermore, it was easier to fit a carburetor and an exhaust pipe because they only had to make a 45 degree turn in the ports to get these things horizontal - - simple! It also precluded the problem fitting more massive motors under the gas tank.

Apparently, someone discovered, probably BSA, that a flatter combustion chamber allowed higher compression and made more power than the high pent roof 90 degree hemi. Hence the Gold Star had a shallower included angle (not sure what angle they started with.) Then BSA discovered that by offsetting the ports at an angle induced swirl which further enhanced combustion efficiency.

I think they knew that with the reduced included valve angle, they could get more power, but the size of the ports became a problem with the larger motors, again because the gas tank and top frame tube restricted the overall height of the motor, so the head space above the valves was minimal. So the Gold Star begot the BSA B44 which of course was a unit motor and cheaper to build, but they didn’t solve the head space until 1971 with the B50 which has a 67 degree included valve angle plus more head space allowing somewhat larger ports. Additionally, they added back the 3rd bearing on the crankshaft (per the Gold Star motor) which greatly improved the rigidity, without even changing the crank itself from the B44.

And as you know, the A65 although it has a shallower combustion chamber compared to the Triumph due to the reduced included valve angle, still did not have the raised head space like the B50, so you just can't enlarge the ports in the upper direction without running into the valve spring pockets, and if you enlarge towards the pushrod tunnel, you break thru there, and similarly, enlarging outward breaks thru the finned area as Mark had found out, unless you first build up that side up with weld, although I admit I haven't built a performance A65 - - - - yet!

Then we have V-twins like Harley, who probably stuck with flathead motors rather than improve on the knuckle head overhead valve motor due to expense. Interestingly, using the V configuration would have allowed more head space to enlarge the ports vertically, but Harley chose to copy the Gold Star with their "modern OHV motors" (according to Keith Cameron) so some things were improved but not everything. The 45 degree V design pushed the cylinders so close to each other as to require an even more torturous intake port with 2-90 degree turns. I'm surprised that no one has tried reversing the intakes and exhaust functions like Alp has done with his Triumph twins, which would seem to allow almost vertical intake ports and fewer problems getting the exhaust (much smaller than the intake ports) snaked out thru the sides of the heads. Yes, they did produce the XR or whatever it was called with the rear cylinder set up that way, but it still left the front cylinder's intake with some fitting issues. But if you look at a modern Harley intake port, you can drive a truck thru them compared to our British heads.

Now we look at modern 4 valve dual overhead cam motors, short stroke multi-cylinders to allow shorter overall height, nice flat combustion chambers, tumble instead of swirl induced induction, higher rpm with multiple crank bearings, electronic fuel injections, and say why didn't they think of that sooner? (I'll leave out the bad idea of a single overhead cam design putting the cam in the hottest part of the motor but still using rocker arms. Stan Millard proved that when his B50 flat trackers could outrun everything including Yamaha TT500s and the Rotaxes.) But as we are stuck on our old Brit designs, we suffer on doing the best we can.

Incidentally, as I don't have my own thread here, so I'll tell you what I did with my TR25 motor (BSA B25). I cut off the intake flange, moved it up about 3/16", and bored out the intake to 31.5 mm before breaking into the valve seat area. I then tried going sideways but broke thru the finned area. I use a Carillo rod, JE piston, Titanium valves (made from used Chevy NASCAR valves), Megacycle cam, chrome moly pushrods, and a Mikuni 34mm flat slide carb. These improvements along with smaller wheels, longer swingarm, and a narrower width allowed me to set a new record at Bonneville (SCTA) last weekend, of 95.2 mph breaking a 10 year-old record. I reached 97mph on my down run, but blew the mile-two back-up run when my fuel filter became clogged with rust, so I had to settle on the 1st mile 95 mph speed on both runs. So we can still improve.

Here is a photo of the bike with an AMAL GP carb, which I couldn't get to work properly.

[Linked Image from i.postimg.cc]

Here is another photo showing the finished port.

[Linked Image from i.postimg.cc]


Tom


Last edited by koncretekid; 09/20/19 2:41 pm.

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Re: The what if A65 67hp challenge. [Re: Mark Parker] #784858 09/20/19 4:52 pm
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Hey Mark

I am curious how you measured your port volume earlier. I’ve yet to try a new to me method using a rule and a burette.

Another question (thanks for entertaining my questions)
Airspeed? I haven’t seen you mention your targets... I am working with figures from other race engines hitting 108 and 112 VE that see 630-640 limiting port velocity.
A contact in NASCAR related to me 650 is target and in some cases close to 700..but these number normally choke most engines.

I tested the stock A65 heads and their potentials. Your CFm numbers are huge compared to my calcs for needed cfm at top rpm.

Lastly ( thanks again) How are you hitting these piston speeds!?
I’ve decapitated many pistons attempting over 4200fpm. I’ve learned the hard way 4000-4050 is the threshold for most engines with “performance” pistons. My custom made pistons can take 4500fpm but not my crank (500 single)

Thanks for sharing all this..I am really anxious to see how it pans out. You’re steps ahead of me.


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Re: The what if A65 67hp challenge. [Re: Mark Parker] #784860 09/20/19 4:58 pm
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Congratulations on the record. Were you in modified class ?


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Re: The what if A65 67hp challenge. [Re: konon] #784882 09/20/19 8:27 pm
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Originally Posted by konon
Congratulations on the record. Were you in modified class ?


Thanks for the complement. 250 M-PG, which is 250cc M (modified stock frame with 4" extended swingarm), Pushrod motor on event Gasoline (ERC 110K which is about 110 octane). Bore is stock as is stroke. This same bike went 100mph at Loring, ME at the 1-1/2 mile, but of course at lower altitude.

Tom

P.S. Denis, I calculate the average piston speed of my B50, 90mm stroke at 7500 rpm to be 4425 fpm, and my TR25, 70mm stroke at 9500 rpm to be 4370 fpm. Both motors have Carillo rods and JE pistons with stock cranks.


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Re: The what if A65 67hp challenge. [Re: Mark Parker] #784893 09/20/19 11:03 pm
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Denis I just used a measuring cup to get a rough idea of port volume. With airspeed I'd read that the stock heads do not have high airspeed. With flow to rpm you can set yourself a limit below maximum power rpm, I've revved my 89mm stroke A65 to around 8,000rpm if you look at the graph above it make good power below that and though the dyno operator wanted to rev it more to see where power would start falling off I chose not to. It probably breaths beyond what it needs to but I doubt there is a reason to have it breath less, I doubt it would gain anywhere from breathing less. It just pulls well from virtually nothing, usually not below 2,500.


mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #784913 09/21/19 2:30 am
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Originally Posted by Mark Parker
With airspeed I'd read that the stock heads do not have high airspeed. With flow to rpm you can set yourself a limit below maximum power rpm, I've revved my 89mm stroke A65 to around 8,000rpm if you look at the graph above it make good power below that and though the dyno operator wanted to rev it more to see where power would start falling off I chose not to. It probably breaths beyond what it needs to but I doubt there is a reason to have it breath less, I doubt it would gain anywhere from breathing less. It just pulls well from virtually nothing, usually not below 2,500.



Mark, Maybe you have your figures crossed? Low-er airspeed higher potential RPM peak power...Higher airspeed lower potential peak RPM horsepower. (I use the Lower=Lazy and Higher=choke)
If the airspeed is too high for a target RPM the intake port will choke. This is usually at .5-.55 mach or roughly 650 fps in my garage.
I tested a box-stock Hornet head with 30mm ports at 725 fps through the 30mm AMAL. On paper and on the dyno the bike made peak power at 7000 on the dot. The intake airspeed limited the RPM potential.

4600 feet per minute piston speed!!! Holy how! I have destroyed pistons from JE, Wiseco and all the other wannabe's trying to attempt this. Trying to meet Nascar/F1 figures of 4800. A great friend and veteran engine builder has found the happy medium for an overdeveloped AHRMA 350 single to be 4200. (42.2 hp at the rear wheel). Based on his racing experience I found 4000-4200 to be the maximum average. Beyond that parts take on new shapes. I shoulda kept the bits for decoration.

4600 is a dream goal! That makes for a stock stroke A65 9450rpm - A screamer. I need your metal recipe. I have been leaning for a source of maraging steel that is not trying to take my retirement in payment

I really appreciate you sharing your work. It is great to have another person as crazy as some of us to uncork the potential of the A65


Full time classic motorcycle mechanic and enthusiast to a fault
Re: The what if A65 67hp challenge. [Re: Mark Parker] #784921 09/21/19 3:20 am
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I used to run a round ported head on the 883 when it was 810cc the head used 44.5mm intakes with 38mm carbs it made power to around 7500rpm 55hp on the data logger. I fitted the big bore cyl and though it had more power on the data logger it was below 6,000 and around 60-65hp. I fitted offset rocker buttons and moved the power up to 65-6700rpm and over 70hp on the data logger, then it fell away sharply. It was good up to there. That head flowed around 160cfm. When I oval ported it the port volume was the same, as was the valves and carbs but flow is now around 200cfm and it just makes more power and keeps pulling to higher rpm. I'm using JE B44 pistons in a Nicasil bore and alloy drag race rods plus 90degree crank which reduces dynamic load by around 45%. Whatever the air speed is in that head doesn't seem to hinder it. I'll just try the good flowing little head on something and see what it does.


mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #784931 09/21/19 6:46 am
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Denis, what hp did you get from the Hornet? Do you have graphs? My plan is to test my stock, other than a roller conversion, 650 Firebird with one or two small oval port heads and see if I can get 59-60rwhp, equivalent to around 67hp at the crank.


mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #784952 09/21/19 12:30 pm
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Hey OT!, Nice work with the 250! Hope to see you next year. PRT

Re: The what if A65 67hp challenge. [Re: Mark Parker] #784961 09/21/19 2:26 pm
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Tom, have you been able to get any of the dyno readouts on the turbo or the MPG bikes?


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Re: The what if A65 67hp challenge. [Re: Mark Parker] #784986 09/21/19 7:21 pm
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Originally Posted by Mark Parker
Denis, what hp did you get from the Hornet? Do you have graphs? My plan is to test my stock, other than a roller conversion, 650 Firebird with one or two small oval port heads and see if I can get 59-60rwhp, equivalent to around 67hp at the crank.



Like an idiot I gave the original to the owner and since I have tried to get a copy from him with no luck. I'm gonna ping him again.
It made 52 hp/7000rpm at the rear wheel on a Dynastar dyno. I was surprised. I did not expect over 45
The only deviation from stock was the carbs - AMAL Concentric 30mm.


My head is spinning! I have been running numbers on your engine and I am super impressed/motivated! Your motor is blowing my mind. Back to the drawing board for me..


EDIT:
I was wrong- The gent reminded me on a call last night. I had apparently told him the motorcycle might make 35 hp and it made 42 - not 52

Sorry all. I'm the guy with his foot in his mouth today.

Last edited by Denis J; 09/26/19 3:48 pm.

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Re: The what if A65 67hp challenge. [Re: Mark Parker] #785047 09/22/19 4:34 am
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If you were getting 52 brake at the back wheel from a STANDARD 650, you were doing bloody well with an a65!
It took me a damn long time to get much more than that from a very modified 750 kitted one. I remember being very
pi$$ed off getting around 55 after all the work we'd done, another 2 years before we saw 60 and that was at 7500+.

Re: The what if A65 67hp challenge. [Re: koncretekid] #785051 09/22/19 5:39 am
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That's very impressive from the 250 KK. Do you have any flow readings on the head or any dyno graphs?

I'm looking at one of, I think Pushrod Tom's, dynographs from the Hornet in 2010, two runs on the graph the difference being 250 and 260 mains. It has a graph of air fuel. If both are being graphed in real time it's interesting seeing the power loss with too rich and too lean conditions.


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Re: The what if A65 67hp challenge. [Re: Mark Parker] #785064 09/22/19 11:11 am
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Originally Posted by Mark Parker


I'm looking at one of, I think Pushrod Tom's, dynographs from the Hornet in 2010, two runs on the graph the difference being 250 and 260 mains. It has a graph of air fuel. If both are being graphed in real time it's interesting seeing the power loss with too rich and too lean conditions.

So are they 60 hp?


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Re: The what if A65 67hp challenge. [Re: Mark Parker] #785065 09/22/19 11:20 am
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If they were 2010, I would say no. PRT

Re: The what if A65 67hp challenge. [Re: Mark Parker] #785067 09/22/19 11:40 am
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Not this one, it's from 2010, 51.32rwhp. Hope it's ok to put it on here. It's interesting the difference of one jet size. Around 12.5-1 is supposed to be the best air/fuel ratio for power. My 883 was too lean on the dyno the richest it got which was at over 7,000 and was 14.4-1 which is way off, it started massively lean then gradually got richer as rpm rose, but I don't know just what that means in hp loss. I did notice an improvement through the mid range with richer mains.

[Linked Image from i.postimg.cc]

I'm hoping Tom might share his latest graphs which are at higher power levels. For perspective the best stock Commandos are around 48rwhp.


mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #785069 09/22/19 12:43 pm
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I saw Tom's Hornet at the land speed racing track two times he raced in the same class as my 650 Triumph I believe the Hornet engine is modified, quite a bit modified at least by 2017....At any rate no BSA has been able to catch my Triumph at 133 mph or Kevin Roberts Triumph at 135 mph...Just some good natured prodding here...


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Re: The what if A65 67hp challenge. [Re: Mark Parker] #785183 09/23/19 11:35 am
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You Triumph guys are what propels my efforts. Not an easy task! I'm pretty sure we can do it but everything must be perfect as you know. That picture is a great bit of nostalgia and a reminder of where we were back then although it does not tell the details which were more complicated than dyno work. I would say that 12.5-12.8 is a good target for straight up race gas but some of the fuels we use want more. PRT

Re: The what if A65 67hp challenge. [Re: Mark Parker] #785282 09/24/19 2:57 am
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Thought I'd measure how much could be added welding in the pushrod tunnel where the port breaks through. It could be widened an additional 10-12mm without problem. The port doesn't need to be that much wider but a little more might be good.

Just for curiosity I measured flow through the port with a stock 40.5mm valve. The bench hasn't been calibrated for a few days but it probably doesn't matter that much for this experiment, and bear in mind that the port entry and carb required is 34mm.

With bare manifold 146.5cfm, with bell on manifold 156cfm. Oversize valves are not that necessary but they give extra flow and compensate for worn seats, they may also work better at low lifts. I don't really get this, you would think the valve at .385" lift would be far enough away to make no difference, but obviously not, the back of the valve is very much in the equation. The 42mm MAP valves have a very fine swirl pattern, I polished it off one of them and made it very smooth and shiny, it flowed a little less, so obviously the valve matters, size, shape and texture.


mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #785287 09/24/19 3:52 am
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Re: The what if A65 67hp challenge. [Re: Mark Parker] #785323 09/24/19 1:35 pm
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That is interesting DM. What they haven't got is a port shape anything like the stock A65, that is at such a low angle and aimed across the valve, they only show ports that aim at the back of the valve. They compare oval ports to round ports and they work largely the same except one is higher. And the BSA head has no height and a very compromised approach to the valve, I'd love to see a simulation of that flow.

You can see the flow pattern around these valves in the article is pretty uniform, right around, the stock BSA flow around the valve would not look like that. In the article big valves near the edge of the head are less uniform. Using an oval port in the confines of the BSA head allows the port to turn onto the back of the valve and use flow around it more uniformly, when it does so there is a big jump in flow. The air can get through the valve the way the valve is meant to work.

Big valves work to a degree in the BSA because they have more area for flow, though only on that part of the valve where air goes through, so a 44.5mm valve can flow about the same air, predominantly through one side, as a 40.5mm can flow, when it does so uniformly around the whole circumference. It's just a matter of seeing how that translates to an engine in use. The guys that work with Norton heads try to keep their ports smallish, because they want to maintain the Norton's strong midrange with a limited rpm ceiling. So unless they short stroke them, or go for 900cc+ they do not use super big ports and valves. The best stock Commando head flows around 123cfm I think. They use smaller valves than the stock BSA's 40.5mm. I'll have to go visit their site and see what they get from a similar valve size.

I expect there is a port size to valve to carb to flow that is optimal. Not sure what it is without simply experimenting, and the BSA head gives plenty of options for levels of flow.


mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #785388 09/25/19 7:26 am
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A calculation from Superflow for RPM versus CFM can be found here:
https://www.cartechbooks.com/techtips/cylinder-head-math-for-engine-performance/
VE Factors

1,196 = stock engine

1,256 = street/strip engine

1,316 = race engine

RPM = (VE factor ÷ displacement of 1 cylinder) x CFM

So for a stock engine the peak power engine speed should be
1196 / 20 * 107 = 6398.6
(only valid for 28 in measurement)

Another SuperFlow-sourced formula along the same lines uses airflow through a complete system to predict peak horsepower.
Horsepower = observed CFM x power coefficient x number of cylinders

Power For Flow at Coefficient Inches of Water

0.43 10

0.35 15

0.27 25

0.26 28

So for your measurement of a standard head with everything attached (manifold and carb) the HP is
HP = 107 * 0.26 * 2 = 55.64

Re: The what if A65 67hp challenge. [Re: Mark Parker] #785403 09/25/19 12:23 pm
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Yes it's interesting isn't it. It's so fundamental. The key to engine performance. I doubt it's fully understood by many people, the fact that where an engine makes power is totally related to how it breaths. It's not the cam that determines at what revs an engine makes power, it's only a minor player compared to the cylinder head's ability to breath.

I think your hp calculation is for a fairly hot race engine.

In the Wallace Racing calculator for a street/strip motor, their mildest tuned, to hit the target 67hp would need 145cfm and would be around 8,000rpm in an otherwise stockish motor. The Lightning head I've done should do that through a carb quite easily.

The Thunderbolt head at 168cfm, if that was available through a good breathing carb, predicts 80hp beyond 9400rpm. So the Thunderbolt head would be more suitable for a 750 running to 8500, that would be similar power to a Z900 Kawasaki. High compression, 11-1 or 12-1 and a good exhaust would qualify it as a race engine, the cam would need retarding to clear the valves and power could possibly reach the 86hp predicted at around 8,500 which is reasonable rpm more suited to a 90 degree. Plus the 34mm port is small enough that midrange should be great. Possibly this would be the most sensible spec for a sweet A65 engine that would last, as a 750 big bore using B44 pistons 10 or 10.5 -1 compression should give no problem on the road on premium fuel.


mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #785764 09/29/19 4:23 am
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This is Ben's 750. We are still trying to work out the needle jetting. We have a wide band o2 sensor in a header plus an air/fuel gage tied to the dash. Transition from pilot system to needle goes through excessively rich to lean unless you get the spot on the needle where it's good. I might get some new needles and modify them a little where needed. The carbs are 38mm flatslides on a large port head with 44.5mm valves, that flows around 180-190cfm. The RGV chassis gives super handling and brakes.

[Linked Image from i.postimg.cc]

Video:

https://www.youtube.com/watch?v=hmF...AGlOVpL7r6NduE_rxFCw80glxWLO03FIBLRO9T74

Last edited by Mark Parker; 09/29/19 4:41 am.

mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #785779 09/29/19 1:25 pm
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Sounds strong, seams to pull hard. Do you plan to run it on a dyno ?


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Re: The what if A65 67hp challenge. [Re: Mark Parker] #785834 09/29/19 11:27 pm
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Maybe.

Jan from Sweden posted this on another thread. Flow measurements for the converted small port small valve twin carb head. Using a radiused entry increases flow by up to 8-10cfm. Unless the radiused intake is making more difference than that it's about the same cfm as the bigger port bigger valve later head.

Denis J, Thanks for updating your hp figures, do you think you may have mixed up the gas speed figures as well? Jan's measurements in this small port head are quite different. Wish I had the gear to make those speed measurements.
If the flow is as good and the port smaller, the midrange and bottom end should be stronger as people report. It must have been frustrating for the guys at BSA trying to do this in the '60s without the gear to measure flow.

What Jan measured:

" Just finished a flow test on a small port head, 68-466. Valve dia 1.51". Radiused intake.

Lift [email protected]"

.100" 54.4
.200" 86.3
.300" 109.8
.400" 119.5
.500" 122.6

Average gas speed measured at nine points in the port.
@ .200", 202 ft/sec.
@ .500", 207 ft/sec.

Next test will be with 1.600" intake valve."


mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #786775 10/11/19 9:13 am
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I bought myself a copy of David Vizard's how to port and flow test. Very interesting book.

Interesting section on valve guides. Clearance on the intake guide to valve stem can be .0014"- .0016"
and going to .004" just on the intakes dropped 3hp on a 165hp engine, going to .006 dropped 9hp. K/liners can run as close as .0001" without seizing, but can lose hp because the valve cannot self centre in a heat distorted head and seat. I always use k/liners on my bike because they are precision machined in the head without any distortion from fitting.


mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #786778 10/11/19 9:41 am
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Vizard is a regular and has his own section the Speed Talk web site...


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Re: The what if A65 67hp challenge. [Re: Mark Parker] #787026 10/14/19 2:18 am
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Thunderbolt head photo for DM: Fairing the guide even with plasticine increased flow by about 4cfm. to 172.3cfm @ .385". I have no idea how to add a flair that would not risk getting swallowed by the motor, though the port does go deeper in that area and a ridge can be left it's not that high and it is very difficult to shape. Could make it from JBweld I guess. Welding in the pushrod tunnel and going wider would probably get the same increase in flow, with a slightly bigger port rather than slightly smaller frown So yea fairing the guide would be better.

[Linked Image from i.postimg.cc]

Flow with the 34mm PWK. Knocked back flow to 156.8cfm, there was a square edge at the outer edge of the bell so blended it= 158cfm all without the faired guide, 160.7cfm with it. A 36mm carb I expect would lose less.

Seeing 145cfm should give around 69hp @ 8,000 in a stockish engine this port is well over target.

[Linked Image from i.postimg.cc]

The Thunderbolt head with both ports the same, with twin 34mm carbs on a 750 with higher compression could give around 82hp, swapping to 36mm carbs could give possibly another 5hp, probably around 8000-8500rpm. Or 9,000+ on a 650, it would be fun to put it on an engine and see.

[Linked Image from i.postimg.cc]

In David Vizard's book he allows calculation on port velocity based on port size and also flow, so even though a port is bigger if the flow is up enough velocity is not particularly lost. If the predicted hp to flow seems optimistic in reality it's not, it's just based on a law of physics, or science. Which indicates what can be expected if everything is set up well. It may include variations in the exhaust and other settings to get every last hp out of it, but it should be available.

Last edited by Mark Parker; 10/14/19 3:46 am.

mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #787035 10/14/19 3:51 am
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Actually, the leading edge of the fairing ahead of the guide should be rounded like an airfoil. Having a sharp edge will be critical to flow angle and you could loose flow from separation. The downstream side of the guide can be filled in the width of the guide back to the bowl with a sort of sine wave shape blending it into the bowl and rounded on top. This area is in the wake of the valve stem which can be oscillating or turbulent depending upon the Reynolds number.
[Linked Image from labman.phys.utk.edu]
The swirl scratches in the valve stem below the guide increases the turbulence and energizes the boundary layer which delays the separation around the stem, effectively increasing the Reynolds number so you get the smaller turbulent wake shown in No. 5 rather than the larger oscillating separation shown in No. 4.

Re: The what if A65 67hp challenge. [Re: Mark Parker] #787041 10/14/19 9:39 am
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DM the way it is with the sharp edge is working, the photo distorts it a bit the sharp edge is lined up central with the guide, and it is adding flow and taking up space. I have had that sort of thing more curved that messed it up, this is taller though and may be separating the air. If it was tearing across it the flow would be less. I like that it's giving extra flow and making the port smaller, it would be nice if that bit was cast in. But I might be able to make it from JBweld on top of what's there.

It's pretty exciting getting this sort of flow from such a small port and valve at stock lift. #5 might be why the swirl patter valve flows a little better than polished, I was wondering why it was.

I may be able to make a mold to shape the guide fairing in the port.

In Vizard's book he has a ported small port head flowing slightly more than a big port head at all but high lift conditions, on the dyno it has more power right through with 30hp more at the top end, with power hanging in longer. He had also increased compression ratio with the small port head which he said would account for 10hp.

Last edited by Mark Parker; 10/14/19 10:50 am.

mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #787045 10/14/19 12:13 pm
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Originally Posted by Mark Parker


It's pretty exciting getting this sort of flow from such a small port and valve at stock lift.


How big roughly is the port?


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Re: The what if A65 67hp challenge. [Re: Mark Parker] #787076 10/14/19 8:09 pm
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It would be interesting to see the effect of a tapered "fairing" on the engine side of the valve guide, it would give a more streamlined shape


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Re: The what if A65 67hp challenge. [Re: Mark Parker] #787083 10/15/19 12:21 am
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It's faired both sides of the guide with plasticine, but it would raise a bit of a problem removing the guide, as it would need a punch with a very small ledge.

Allan its a 42mm valve, where the port enters the head it's 28X34 the carb is 34 but probably should be 36, then the taper from 36mm would be perhaps more ideal and boost the top end. So this is just trying to get the best from this valve size, and probably less applicable to a 650 unless it's built to for 9,000rpm.

I'll measure the port volume when I'm done, just making the guide fairings waiting for the JBweld to set. I put shrink fit over the end of the guide and modded the punch for removing it. The easy in and out guide has a reduced dia. but I need to leave it alone till tomorrow.

Volume measurements are a bit difficult because the ports on a Lightning are longer, and the stock Thunderbolt is 27mm. But seeing flow is increased by at least 50% air speed in the port should be good. If you have ever ridden an SV650, although it will pull a lot of rpm with very good power, it's also very good in the mid range where most people run them. It would be nice to get a nice power spread similar to that.

Bit of an update:
The fairing on the guide stole cfm, I still have a little there. The plasticine ones looked like a gain but I think it was miss-reading. I tried a few things, deepening the bowl a little more and making the bottom turn less sharp but only gained 1 or 2cfm. I think it needs to go wider. That's where the most notable gains were so I'll widen toward the fins; it must be close to breaking through but it's easily patched if I do, and see what happens. It's got good flow at .300" valve lift but not much gain higher than that even though it gets a lot noisier. Maybe air is tearing off the tiny fairing that's still there?

I definitely put the test cyl the wrong way in my fixed bench, it would be better with the inlets facing out, easier to see in and hold some strands of thread in there to see the direction the air's flowing.

Added vac #4 so I can test at an actual 28"W and above. Might start comparing low lift values at 100"W to replicate a running engine, TDC on overlap can have 100-120"w by mid intake stroke it has reduced to 15-20"W. Low lift flow is important to making the best power, might as well see what can be done in that area, esp when cutting the seats. Probably shouldn't test at night, turning all 4 on at once will probably dim the neighbor's lights frown

Last edited by Mark Parker; 10/16/19 11:08 am.

mark
Re: The what if A65 67hp challenge. [Re: Mark Parker] #788129 10/25/19 11:36 am
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These are a few different inlet valves that can be used in the A65 head. On the left is an early small port 37.2mm intake, the later 40.5mm intake, 42mm MAP, a 44. something, slightly smaller than the last which is a Jaguar 44.6mm. The head underneath is a small valve A65 Star Twin modified with welded on stubs for a Webber carb.

The 37.2mm valve is new and was with some parts I obtained years ago. It seems to be A65 and fitted the Star Twin's stock seats. I was able to get 130cfm through the valve reshaping the port a little, but not filling the floor. The 40.5mm was better once the seat was opened appropriately for it, and with the floor lifted now gives 152cfm at stock .385" lift. At .500" its 156cfm. Low lifts seem like they will be good .200" is 113cfm .250" - 129.6cfm .300" - 144cfm.

[Linked Image from i.postimg.cc]

Last edited by Mark Parker; 10/25/19 11:37 am.

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Re: The what if A65 67hp challenge. [Re: Mark Parker] #788131 10/25/19 2:01 pm
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Allan Gill Online Happy
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Nice reporting Mark, I bought the forementioned book and already had a read through it, but will go through it again and probably several times trying things as I go. There is also a mention about valve shapes (applogies if it isn't from this book but if not I have the link on my phone for the page going through it) it links the "tulip" or flute of the valve vs the port height in relation to the valve seat. In short, the lower the port on the head the flatter the flute.


beerchug
Re: The what if A65 67hp challenge. [Re: Mark Parker] #788191 10/25/19 11:45 pm
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NickL Offline
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It's funny really, all those years we used a t'bolt head and everyone without exception told us we were daft
and that the twin carb one was much better. I actually made up a twin carb head to use the weber on, it was
fiddly to do as the tubes angled inwards but i thought as the downdraft was better it would improve things.
I admit it never got the full works like the last parallel port one we used but it was noticeably slower and as the
carb sat higher it was more awkward in use.
The flow bench testing is very interesting reading, the lower lift figures are what impresses me. You don't need
big valves or hairy cams with flows over stock at .200.
Bloody triffick work Mark! (Don't tell SRM or they'll be pirating it.)

Re: The what if A65 67hp challenge. [Re: Mark Parker] #788230 10/26/19 11:20 am
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Really enjoy this Mark. Your flow rates from a 2 valve head are amazing.
The star twin head should give good power and not lose torque.


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Re: The what if A65 67hp challenge. [Re: NickL] #788232 10/26/19 12:30 pm
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Originally Posted by NickL

The flow bench testing is very interesting reading, the lower lift figures are what impresses me. You don't need
big valves or hairy cams with flows over stock at .200.
Bloody triffick work Mark! (Don't tell SRM or they'll be pirating it.)

Yes, many overlook that the valves spend far more time at low lift than full lift as the engine cycles.Once the carbs and intakes are in place and how the flow reacts as it enters the cylinder and is confronted by a moving piston, figures can change a bit...Now Mark need to build a test mule to see what the head will do in real life. Should be interesting..


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: The what if A65 67hp challenge. [Re: Mark Parker] #788294 10/27/19 2:45 am
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Shall i tell 'em Mark?

Re: The what if A65 67hp challenge. [Re: Mark Parker] #788309 10/27/19 6:06 am
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Yea for sure Nick.


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Re: The what if A65 67hp challenge. [Re: Mark Parker] #788310 10/27/19 8:18 am
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NickL Offline
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Well, Mark has very kindly agreed to do a head for this outfit i am preparing for next years season.
Although i'm unfortunately not riding the old beast, i have been doing some work on it for a while.
He got a 2nd place in the Aus titles last year as a 650 only being beaten by a 900cc highly illegal Norton thing.
The chap is a good rider and has had some success with it so far and really wants to have a crack
at the aussie titles next year. It's a period 3 (pre-62) road race outfit a 'sitter'. Based on a Manx Norton
frame and LL forks etc.
The engine will be an end fed A65 with A10 crank and A70 pistons around 750cc.
I just can't get these things out of my system............so as an old fart at least i can get to prepare and watch.
I know Marks work on the head will be a huge boost on the old girl.

https://i.imgur.com/qLfbAAW.jpg
https://i.imgur.com/MXirxGr.jpg
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Re: The what if A65 67hp challenge. [Re: Mark Parker] #788312 10/27/19 8:50 am
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Hi

Good stuff Nick, look forward to seeing it all built up and as you said with Mark's head work as well it should be a go'er.

regards

John

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