Camshaft choice - especially 2S

Nourish said:
Is sarcasm lost on the Americans?
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1709902751727.jpeg


Why yes, sometimes it is.

Webcam 312

I chose not to use it, went with stock.
 
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MichaelB said:
One has to be from certain generation to really appreciate Wally.. :D :cool:

Why not the 312?
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More so Eddie Haskell who was more interesting.

Like the original query about 2S, the Web 312 is stronger in the upper RPM's. It's well known the stock cam is very good choice for a street bike, so it's a matter of choice. There's not much to be sorry about with any of the cams mentioned, just that you need to balance higher lift/ longer duration cams with other engine enhancements.
I'm going with the 312 in my 750 rebuild. Comnoz liked it for my build with his flowed head, Keihin FCR's and Carrillo rods.
 
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You're right!!! Wally was the brother...
So much for the memory... :D
 
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concours said:
Serious question.
Yes, I know the science involved, Dad splained it to me when I was 10-12 years old.
Which of the FE engines used the sodium filled valves?


I think @acotrel has some very fascinating experience/knowledge that needs to come out and enlighten us.
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I recall the exhaust valves (might have) in the Tunnel port heads for the 427 and maybe the SOHC 427 used the sodium filled items.
I would imagine anything Nascar in the 1960's (Ford 427) got them but would be a guess at best and most likely changed out after every outing.

As far as ACotrel, he had probably experienced more than a lot of the stone throwers here, I read his postings. What is digested from them is up to the individual.

As far as the 2S camshaft, no thanks.
The stock grind is fine for a road bike.
If I was to replace the camshaft it would be the billet version (over chilled iron) from Newman Cams in the UK, if money was no object, it would be the JSMotorsport with the BSA lifters also in the stock spec.
 
Time Warp said:
I recall the exhaust valves (might have) in the Tunnel port heads for the 427 and maybe the SOHC 427 used the sodium filled items.
I would imagine anything Nascar in the 1960's (Ford 427) got them but would be a guess at best and most likely changed out after every outing.

As far as ACotrel, he had probably experienced more than a lot of the stone throwers here, I read his postings. What is digested from them is up to the individual.

As far as the 2S camshaft, no thanks.
The stock grind is fine for a road bike.
If I was to replace the camshaft it would be the billet version (over chilled iron) from Newman Cams in the UK, if money was no object, it would be the JSMotorsport with the BSA lifters also in the stock spec.
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This is supposed to be supportive but may not sound like it.

Getting the stock tappets radiused by Newman Cams and using the stock push rods would be fine for a JS0 cam in a maturely ridden road bike.
 
I was a teenager in the 1950s. I failed most of my Matriculation exams because of old racing motorcycles, then spent most of my life studying while working. Some of the older guys back then were worth talking to. I thought Baldo Meli was insane - he worked in the Triumph factory and got a 12th on a rigid Triumph on the IOM. But as I got older, I realised he was not mad. One of the guys inour local Japanese bike club, helped Ron Miles race. Ron was killed in the UK in the 1950s. There was a thing about Australian Manx Nortons - they had Symco con-rods and could be revved reliably to 8000 RPM.
I probably think a bit differently from other guys. I was trained to be a scientist by Nazis and Jews.
 
I have wondered if the con-rod lenght to stroke ratio in a Commando motor is similar to that of the short stroke 500 Manx. One of my friends had a long stroke Manx - the short stroke Manx was faster.
 
acotrel said:
I have wondered if the >>>>con-rod lenght to stroke ratio<<<< in a Commando motor is similar to that of the short stroke 500 Manx. One of my friends had a long stroke Manx - the short stroke Manx was faster.
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That would of course depend on the >>>>stroke and connecting rod length<<<<

Sunbeam 500 twin- 70 mm x 63.5 mm
Late Triumph 500 unit 69 mm x 65.5 mm
Norton Commando 750 73 mm x 89 mm
Triumph pre unit 650 71 mm x 82 mm

Even the OHC Sunbeam engine has a >>>>better ratio<<< than the Commando.
SB6.JPG


Edited with highlight >>> <<< for the folk who cant read or skim over posts. :)
Connecting rod ratio (connecting rod length divided by the engine stroke) equals slower into and out from TDC and more dwell at TDC.
 
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I have a brand new Newman cams 2S cam (steel, not chilled iron) going cheap if anyone is interested (NOT because I don’t like 2S cams, just cos I’ve too many in stock)…
 
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Time Warp said:
That would of course depend on the stroke and connecting rod length.

Sunbeam 500 twin- 70 mm x 63.5 mm
Late Triumph 500 unit 69 mm x 65.5 mm
Norton Commando 750 73 mm x 89 mm
Triumph pre unit 650 71 mm x 82 mm

Even the OHC Sunbeam engine has a better ratio than the Commando.
View attachment 113059
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I suggest that ratio affects torque. My short stroke 500cc Triumph motor had the 71mm rods with 63mm stroke. It was all top end.
All that stuff is very old technology, however that does not mean it was not good. With different cams, it is probably possible to end up with a contradiction - one effect opposing another.
 
Since the topic seems to have shifted to rod ratios or possibly bore stroke ratios-

I suspect Al's Triumph had much longer rods than 71 mm. That is less than 3". That number has to be the bore for the 650 Triumph.
It appears that all of the ratios listed above, eg. Sunbeam twin 70 mm x 63.5 mm etc, are all bore and stroke ratios and really have nothing to do with rod ratios.

Iirc the stock Commando has a rod to stroke ratio of 1.68.
Some say this number is too small, others say it's about ideal for a road engine.
My Mazda 2.5 auto uses rod ratio of 1.54, substantially lower than the Commando ratio. The Mazda revs higher and makes a lot more power per cc than the Commando. It should continue doing that for over 500,000 kms, if our last Mazda is any indication.

I don't think there is anything wrong with the rod ratio of the stock Norton.
There are lots of successful engines that use a similar or lower rod ratio and many have a higher redline than the Norton.

The bore /stroke ratio of the Commando 850, 77mm x 89mm is not good for a high rpm engine, but the stock road engine isn't a high rpm engine.
The bore/ stroke ratio of the 650 ss is much worse than the Commando, however even that doesn't seem to matter for road use as the 650ss is a fun little, quite revvy engine.
The Sunbeam might have a " better" bore stroke ratio than the Commando but with 25 hp and a 75 mph top speed the Sunbeam is not an exciting machine, the Commando is.
 
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The rods in my 500 Triumph engine were 650 rods and all the other parts were 650, apart from the crankshaft which was a billet and had 63mm stroke. The barrels, pushrod tubes and pushrods were all 12mm shorter. In a featherbed frame with 4 inch megaphone exhaust, that motor was really dangerous. I learned a lot, but it is not the way to go racing. Even thinking about it does things to me. - Racing my Seeley 850 is dead easy when compared to that. It was really strange, that motor was good on a very large circuit, it seemed to keep on accelerating forever - but it really needed 6 speeds close ratio.
Percy Tait must have been a real hero.
 
With my Seeley 850, everything I have done has been about making it pull harder. With the increased trail on the steering, I can accelerate through corners from beginning to end, so I do not need so much top end.
If you pick the slowest corner on a race circuit and wait until you are half-way through it, then use more throttle - you will see whether the bike tends to either run wide, or steer more in the direction you want to go. If it runs wide, you need more trail. With more trail, you will find the bike will stay more upright in corners and you can gas it much harder. You need strong smooth power delivery. A Commando-based bike is very different to anything which is Japanese.
The cam determines the shape of the power band, a two into one exhaust can help cornering to be faster. It is the combination of both which is important. It probably does not matter which cam you use, you can make an exhaust system to suit it, but you do not need a big burst of power at 5000 RPM and nothing under it. You do not need a bike which might grab you by the throat, in a corner.
The gearing of the bike must suit the motor. My gearing is absurdly high, but the bike accelerates from the beginnings of corners. So the motor winds up for a much longer time. Close ratios are better. I change gears as I accelerate through corners.

I know I have to race again - I had them all cold the last time, with all the tight parts of Winton ahead of me, and the fuel line came adrift. The bikes in that class are mostly 4 cylinder superbikes of 1100cc capacity. Down the straights, they really get mobile.
 
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When I raced my 500cc Triton, I was terrified of being balked in corners. If I backed-off and slipped the clutch to get going again. the bike would always go sideways. If I race again, there is no way I would ever crash. My wife's fears are completely unfounded.
When you watch road racing, what you see is not what you get.
 

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