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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.


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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.


79 T140D, 96 900M Ducati ,2001 Sportster....On a bike you can out run the demons..
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


79 T140D, 96 900M Ducati ,2001 Sportster....On a bike you can out run the demons..
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 ,2001 Sportster....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.

mark
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...


79 T140D, 96 900M Ducati ,2001 Sportster....On a bike you can out run the demons..
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...


79 T140D, 96 900M Ducati ,2001 Sportster....On a bike you can out run the demons..
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
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