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head design
#824314 09/20/20 11:16 pm
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I am a Triumph guy, I just like almost everything about them, looks were the first attraction when I was a kid in the early 60's. i have a question, which English bikes, Triumph,BSA and Norton have the best head design? Just wondering.

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Re: head design
scott garland #824316 09/21/20 12:16 am
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"Best head design" - for what ??

If its to get from A to B, take your pick ?
If its to unzip it, refurb it and replace and ride off into the sunset, take your pick ?
If its to get to the front of the pack, take your pic ?
If its BMEP and pure horsepower, take your pick ?

Manx Nortons take some beating - on a good day they can achieve better than 100% cylinder fitting.
Bragging rights in the pub, and it took 20+ years to figure it out, but little else these days ??

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Re: head design
scott garland #824319 09/21/20 12:47 am
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Nortons Dominator to Commando had the most effective "semi hemi" head design, with flat top pistons they give the same or better comp ratio as Triumph or BSA with doomed pistons. However every model of the trio has its own week and strong points, so its very difficult to choose the best of them. Triumph in the best looking in my eyes too.

Re: head design
scott garland #824321 09/21/20 2:18 am
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Hi Rohan, The racing success of Triumph are on record. Triumphs sure won a lot of races.

Tiger Cub has same head concept. Did well in light weight class.

The rest of this is just my opinion from observation of other bikes. Take it as that.

Norton Manx was really fast. I don’t know it was sold as street bike really. BSA Goldstar is fast. Was sold as street bike. Several in the club I’m in. A fairly low volume production.

Regarding the mass produced road bike like what many of us have this is my thoughts. Again take it as that.
On the road Triumphs are very fast. They are possibly more trouble free & possibly last the longest. They leak from pushrod tubes & rocker boxes.
They demand high octane fuel.

BSA is a close 2nd. They don’t need as much octane. They are pretty trouble free & last pretty well. Still leak a lot. About equal to Triumph. At least you don’t have pushrod tubes.

Nortons seem fast, but they didn’t win races like Triumphs. No push rod tubes to deal with. Don’t need high octane, an advantage in California. Still they leak a lot. People perceive them as high speed cruisers but it might be just perception due to the isolastic vibration system you don’t feel it straining. The guys that ride them fast don’t tend to find them durable.

I have friends with all the above. Some own each brand. We kick this around all the time. Being equally well maintained that is pretty much how the owners of all 3 see it.

Of course the skill of person maintaining bike plays a huge part.

There is a reason Triumph was so popular. At the same time Triumph had a strong dealer network. .

Back to head the 9 & 10 bolt heads are fairly durable so long as somebody doesn’t damage them with pushrod tube crush. It over grind valves etc. Keep it torqued the head gasket is ok.
The head seems fairly efficient out of the show room as the bikes were quite fast. Other than push rod tubes leaking the Triumph is pretty good in my mind.
Don


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Re: head design
scott garland #824325 09/21/20 2:39 am
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Quite a few years ago a traveling Triumph show went through SoCal. I believe it was for the 100th birthday of Triumph motorcycles. Nicely done. Two or three tractor trailers full of Triumphs and Triumph stuff. There was a bill board of Triumph facts. The one I remember was that at that time Triumphs had won more races and set more speed records than all the other motorcycles in the world combined. Nuff said.


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Re: head design
scott garland #824326 09/21/20 3:07 am
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BSA MC1 248.5cc air-cooled DOHC horizontal single-cylinder with inverted V bevel-gear camshaft drive, four radial valves. 34 HP at gearbox sprocket @10,250 RPM
One problem with the 650/750 twin designs is the wide angle V of the valves. At overlap a good portion of the intake flow goes straight out the exhaust. Late Norton flat top piston design had the flow angled more down into the chamber.
The Rickman (Westlake)-Triumph 8 valve probably second. At least the rockerboxes were integral to the head.
One should note all those Triumph records were with modified engines, particularly the head. A solid block of metal can be modified to be better than a stock Triumph head. Would that count?

Re: head design
TR7RVMan #824327 09/21/20 3:30 am
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Originally Posted by TR7RVMan
Hi Rohan, The racing success of Triumph are on record. Triumphs sure won a lot of races.
Nortons seem fast, but they didn’t win races like Triumphs.

At what level of racing though ??
Nortons competed (mostly) in Grand Prix GP racing - with the Manx.
Triumph didn't even make anything at this level of racing,
(except briefly back in the 40s)

Triumph produced about 10 x the bikes per year that Nortons did, at least.
Swamping the lower classes of racing ... !

BSA didn't ever race that MC1 - mores the pity.
Apparently the Race Shop couldn't guarantee it would win 1st time out, so it never did race.
BSA Gold Stars (singles) won a lot of races in their (suitable) classes.
Horses for courses ?

We still haven't heard from the OP about best - for what ??

Re: head design
DMadigan #824328 09/21/20 3:40 am
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Do we even know what an average VE figure would have been for the '69 and onwards T120's as they left the factory??

Re: head design
scott garland #824330 09/21/20 5:38 am
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??

[Linked Image from upload.wikimedia.org]

Re: head design
scott garland #824361 09/21/20 3:52 pm
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I should have been more specific, I did mean atomizing and filling the combustion chamber with fuel. I have over the years restored or (omg) made choppers and customs out of basket case Triumphs, The domed pistons and the shape of the combustion chamber was what put the question on the back burner of the brain, Spark plug placement and lead time of timing made me question, what the f... were they thinking?

Re: head design
scott garland #824364 09/21/20 4:32 pm
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They were thinking, " Must fit bigger valves ", hemi head gets bigger valves in, at the expense of an orange peel shaped chamber.

The Rudge Ulster bronze 4 valve is probably the best of the lot. Sadly ended with the 2nd World War, when they were taken over to build radar kit.


71 Devimead, John Hill, John Holmes A65 750
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Re: head design
scott garland #824365 09/21/20 4:37 pm
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Originally Posted by scott garland
The domed pistons and the shape of the combustion chamber was what put the question on the back burner of the brain, Spark plug placement and lead time of timing made me question, what the f... were they thinking?

In the 1930s, they were thinking 1930s engine design thoughts, while they designed the head.

In the 1960s, they were thinking about a higher compression ratio, while they made domed pistons.
In


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Re: head design
scott garland #824380 09/21/20 8:11 pm
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In the words of David Minton, the hemi head as used by Triumph was about as revolutionary back then as are modern engine management systems today.
And whatever the shortcomings later on when high compression domed pistons arrived, they were still really fast.
It's easy to praise the virtues of the likes of Norton heads, or the A65, but we still see Triumphs winning.
They can't be that bad.
But which one is the better design as per the OP, is as open to debate as it ever was. Combustion chamber shape isn't the whole story, ports and valves, how swirl is induced by the valves, how the chamber continues that motion or enhances it, how fast it all burns, and how completely it burns. Claiming that a chamber burns slowly based on how early the ignition timing needs to be, is too simple. It's what happens between TDC and about 14 degrees after that matters the most.

As for leaky push rod tubes, anyone who's been around a few Commandos will have sworn at the almost universal head leak from the 3rd rib...
In my opinion and experience, the A65 is the easiest to keep dry.

For what they were, a relatively cheap form of transport or a toy, they all performed pretty well for the day

And I like them all. beerchug

SR

Re: head design
Stein Roger #824390 09/21/20 10:05 pm
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Originally Posted by Stein Roger
In the words of David Minton, the hemi head as used by Triumph was about as revolutionary back then as are modern engine management systems today.

I'd take that statement with a grain of salt - hemi heads had been around for DECADES before Triumphs parallel twins of the late 1930s. Heck, the De Dion Bouton engines had used an ohv hemi engine (of sorts) circa 1900, JAP had hemi head racers in the early 1900s. and Peugeot had a dohc parallel twin (racer) before WW1 that was highly successful by all accounts. Why they didn't proceed with it after WW1 ..... ??
And myriads of folks used ohv hemi's in the 1920s, particularly with racing successes and fast roadsters,.

Even Triumph had a parallel twin in the 1930s before the later successful twins of the later 30s. After the Ricardo model (single) of the 1920s.
I'd suggest it was more a happy coincidence of evolutionary features that made it a mega success, rather than anything "revolutionary" ?
They did work on bumping up the compression a bit though.

The 1930s saw all sorts of engine designs appear, searching for that magic formula to success - a whole slew of square 4s, v-twins, narrow angle v-twins, supercharged 3s and 4s, you name it On top of a slew of different designs in the 1920s
Almost all of forms them have persisted in one form or another through to the present day.....
Triumph have made it a long running formula for success though.

Re: head design
scott garland #824391 09/21/20 10:21 pm
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...regarding the hemispherical heads; is not that what HD and almost all the USA cars had?

Regarding success; besides the racing; marketing etc Triumph had the best looking bikes no doubt. If you check Nortons; they had couple of models or years that were appealing but if you look closer, do not have details; the engines are rough and crude; no subtleties; no nice lines compared with Triumph models. In fact the Triumph 5T from 1938 is one of the best looking motorcycles in all the parts and details.
BSA; well; with those egg shaped bottom ends and top pans how they can attract the customers back then? Not possible to compete with Triumph.
You look at the front mudguards...3 inches from the tyre! and many do not even follow the circumference...
The design department also did not understood the changing squared lines of the 70s but Triumph, yes.

Re: head design
scott garland #824395 09/21/20 11:28 pm
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The A10 was one of the best looking twin engines in my opinion.
Trouble with triumphs was they changed their look as you rode them and more bits vibrated off.
The gold star was a lovely looking bike and the most successful club racer of it's day.
The manx was also beautiful but open valve gear was not really road practical, on the track it
was superb and went on for way longer than it should have really.
Thinking regarding engine design changed and the early design of deep hemi's became old hat
in favour of flatter pistons and shallow 4 valve heads. Things move on.
It all depends on what you're looking for in a bike, triumphs were cheap and plentiful that's what killed 'em.
Nortons were more expensive and stuck to the pre-unit design, beezers went to the Egg shape which
was very strong but not very appealing, Take your pick.........

Re: head design
scott garland #824410 09/22/20 1:09 am
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Bike styling is a long long long way from "best cylinder head design".

Rudge in 1930 had a 4 valve design of bike that was soooo superior to anything else,
it was 45 years before the rest caught up. (and the brits never really did ?).
It came 1st 2nd 3rd in the 1930 IoM TT races, just to demonstrate how superior.

There are folks who have suggested Triumph simply mostly copied this (whole) design,
but substituted a parallel twin for the twin pipe 4 valve engine.
[Linked Image from sunbeamland.com]

I'd suggest this is where the "best cylinder head design" is to be found...
And note the little 'guaranteed 100 mph' at the bottom there.

In this era, they (all) had open valve gear.
In the mid 30s, it became all enclosed - so more civilised.

Re: head design
scott garland #824421 09/22/20 5:53 am
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Yes, they were fitting 4 valve heads on ww1 aircraft engines to get the performance out of them back then.
Probably cost was a factor in the designs, Rudge were an expensive bike in the 30's and it was only just
post depression really. My father reckoned it was all he could do to afford his 500 matchless back then.

Re: head design
scott garland #824428 09/22/20 7:46 am
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He was probably doing well to have been able to afford a Matchy.
My dad bought a late 20s Norton, a new one was well out of reach ..
On the dirt roads common of the era, he said it was a bit of a handful..

I was going to comment that Rudge peaked with a supreme design right at the wrong time.
At the peak of the Depression was not really a good sales opportunity !
And by the time the slump was over, Rudge were rather financially strapped.
If only ...

Of course, this may not sit well with Triumph enthusiasts - but we don't want them to get too uppity !
They definitely had the sales at the end of the 30s to show who was leading in the showroom stakes.
There was a mad scramble after WW2 to produce parallel twins.
And also red motorcycles, another very strong sales trend.
Telescopic forks also became about mandatory.

Re: head design
Rohan #824451 09/22/20 1:29 pm
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Originally Posted by Rohan
Originally Posted by Stein Roger
In the words of David Minton, the hemi head as used by Triumph was about as revolutionary back then as are modern engine management systems today.

I'd take that statement with a grain of salt - hemi heads had been around for DECADES before T.
Nothing in my post suggests that Triumph invented the Hemi or that is was a new development.
The fact remains that it was a sound development for it's time, and the phrase "what were they thinking" from a former poster was totally out of place.

SR

Re: head design
scott garland #824472 09/22/20 4:52 pm
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Triumph Ricardo apparently had a four valve head.

Defining "Best head design" for classic Brit bikes is a wide brief. Velocette.

Re: head design
scott garland #824499 09/22/20 10:40 pm
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The Triumph hemi head was no miracle of design in the 30’s, it was just a part of an engine layout that proved highly successful into the 80’s.

Few engines can claim such a long pure pedigree (I can’t think of another).

So if there’s something you could really criticise about it, it must be that it largely remained the same, which must say something about the original design.

That it could develop from a humble 500, through hot 650 to sturdy 750, without fundamental redesign, says an awful lot.

It doesn’t matter to me that the design needs more ignition advance than BSA or Nortons, so what?
The important thing was that the Triumph was in front of the others on the road!

And though this of course is not an invariable fact, it does apply in most comparable situations.

That will stir up a bit I suspect! Good old bar room banter!

Re: head design
scott garland #824503 09/22/20 10:57 pm
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Just keep making it bigger until you go bust eh?
What a fantastic development philosophy.
Seemed they were not alone in their way of thinking though.

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Re: head design
NickL #824504 09/22/20 11:05 pm
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the side valve is a more practical head .
Quiet and maintenance-free .
it won ww2 ... used on motorcyles and jeeps ...my lawn mower has one .

Re: head design
scott garland #824505 09/22/20 11:10 pm
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Oh yes, nuts to fuel consumption and performance eh?
So practical everyone now uses them?

Sorry but even HD went away from side valves in when,,, about 2018 wasn't it?
Same time as they went to foot change?

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