Camshaft choice - especially 2S

Time Warp said:
If a serious question, it liquefies at low temperature.
The problem is with time they can corrode the valve itself leading to the head parting company.

I know there is at least one other Ford FE (390/428/427) fan here, even Ford who used those valves recommended replacement at short intervals.

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Nice "Jug" in the back ground.
 
acotrel said:
More radical cam timings often give a more pronounced power band. For an adrenalin rush, that is good. But not good when you need smooth power delivery, because you are tyre-dependent. A bike with a bump in it's power delivery is not good in the rain. Or in a very fast corner at high speed. You do not often see guys who ride two-strokes power through corners. With a Commando the next straight needs to begin as you enter the preceding corner. Get on the gas really early. A Seeley-framed bike often comes out of corners much faster than many others. It takes a lot of power on the straights to beat that.
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If you raise compression to compliment the cam grind it will increase cylinder pressure in the mid range, thus increasing torque giving you tractable power on demand as needed.. Increased CR broadens the power band and also give better fuel economy for road use.
 
Dan1950 said:
If you raise compression to compliment the cam grind it will increase cylinder pressure in the mid range, thus increasing torque giving you tractable power on demand as needed.. Increased CR broadens the power band and also give better fuel economy for road use.
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Raising the compression ratio has the same effect as advancing the ignition timing or leaning off the mixture - it increases power if your mixture is slightly too rich. It is the reason engine management systems give more power - they give much better control. Japanese bikes often have more valves in similar capacity motors which give a slight advantage. My mate owns Motec. He was in the UK years ago and fitted an EMS to a Honda, which I think was the one Barry Ditchburn raced against Hailwood at Mallory. Just by putting the injector nozzles in the carb bell-mouths and turning-off the fuel to the carbs - they picked-up a full second per lap.
 
When tuning motors, it is easy to delude yourself. Consider the number of variables in bike set-up, and then the number of variables in intended use of the bike. If you change one thing and then another, you usually get an effect. But in reality, it is the combination of ALL the variables which is important. If you do not have the gearbox, you are behind the 8-ball from the start. The bike must suit it's intended use and the rider adapts to the bike.
Mike Hailwood's Daddy bought him a world championship winning Mondial 250 for Mike to learn how to race. That is smart - let somebody else do all the crashing, and fixing. Marquez uses himself as a guinea pig.
 
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Are
Dan1950 said:
Nice "Jug" in the back ground.
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are you still on about sodium-cooled exhaust valves ? Previously I did not even think about detonation being caused by a hot valve. But I never race using petrol. I knew the Brits used to get their Manxes going quicker on pool petrol than our guys could using methanol in Australia. But I did not think about how they would achieve that. I only ever had one Triumph 650 on petrol which I managed to lean-off, and it became faster. But I did not think much about it. In those days jets were not so easy to buy. The difference between 0,106 and 0.107 needle jets is really big.
 
Fast Eddie said:
Indeed.

I learnt a long time ago that everyone’s favourite cam is the one they’ve got.

And that they all ‘run great’ and ‘pull like a train’ etc.
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As I have said, when I built my motor, I was not particular about the cam. Anything can be made to work well. All you need to do is adjust the rest - exhaust system and gearing, in particular
- and the advance on the cam timing, to suit the exhaust. With a 2 into 1 exhaust system, there is a lot to get resonating, so bigger bangs might be better.
The SS650 was probably the only road-going sports bike which Norton ever made. I suggest 2S cams might have been to Nortons what GP cams were to Triumphs - an E3134 cam was far superior.
The cam in my 850 works well enough - it does not matter to me what it might be. I think it might be SS650.
 
A well tuned 850 motor with a standard cam and megaphone exhausts should be strong enough for anyone. I would not like to race it - it might be too easy to crash. A rush of power when it is not needed does not help anyone. What happens at 5000 RPM in a slow corner might be important.
 
One of the problems with cams has been the closing ramps. At max lift the followers probably be come airborne. If the valve closes too rapidly, it can cause a dropped valve. The ramp on the back of the cam affects the closure rate - it catches the followers as the valve closes. Sometimes it is better to have less lift and longer duration with slower opening and closing rates. It depends on the revs you want to use. A cam which gives good power over 7000 RPM might not do much for a Commando. Longer duration can cause the motor to be peaky.
The flats which appear on cams might tell a story.
 
I have many widely varied interests and am active on multiple forums for these interests. Access Norton is far and away the best of them all, being a great source of knowledge and technical information.... with the possible exception of this thread.
 
I read all of these posts with interest. With these various Norton cams there never seems to be any very distinctive differences. With Triumph 650 cams, the E3134 race cams from the 1954 race kit were fitted to the inlet of the 1959 Bonneville with an E3275 Tiger 110 cam on the exhaust. It gave good performance. When the race cam was also fitted to the exhaust, performance was even better, but a bit exciting. The BSA profile cams did not seem to be as good as the E3134.
With Nortons, there seem to be very few subjective or objective comparisons of the various cams. That might be due to the torque characteristics due to the heavy crank. If you inprove the torque output of a Commando motor, the only way you can realise it is by raising the overall gearing which causes the motor to pull harder and makes the bike faster without increasing the revs.
When you fit race cams to a Triumph, the usable rev range usually goes higher and stronger. You do not need to change the gearing.
I have often felt that my bike was not geared high enough. It always seemed to spin-up at the same rate regardless of the gearing.
I think it is better than any Triumph 650 but it works in a different way.
 
With my bike, I use very high overall gearing with close ratio gears. That removes the throttle response problem. When you do not lose as many revs on up-changes, you get there quicker. If you lose revs on up changes, you tend to use the tapered part of the carb needles more, which richens the mixture. I use slow-taper needles. With a wide ratio gearbox, you lose too many revs. A better cam might do a bit, but the bike can already do what is required. I think the cam I use is a 650ss - it seems to be good enough.
 
I would not say this thread has been a waste. I have learned a bit more about sodium cooled exhaust valves. In my lifetime, I have met some very astute tuners. Most of them would never tell you much. I am not like that, I share anything I know.
 
Deckard said:
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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To be clear, Web makes a 312 cam that is analogous to a stock Commando cam and they make the 312a that is considerably more cam than the 312. The performance cam that COMNOZ would recommend is the 312a. The attached plot is something COMNOZ posted here years ago.
 

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It is not rocket science to get a cam which gives more power at high RPM. But with a Commando engine it might be wise to keep the revs below 7,500 RPM, even with a rebalanced crankshaft. The timings can move the power band. But a gentler cam with more lift might be better. I do not use my Seeley 850 like a normal road race bike. I don't get around the corner and then gas it. As soon as I am inside a corner, I gas the motor full blast. With more trail, the bike can be flicked into the corner, and when it is gassed the back depresses, the bike stays more upright and self-steers in the correct direction - the direction of lean. If I rode the bike like a normal race bike, it would be too slow. It took me a while to twig to what it does. A normal idiot does not gas the bike so early in corners.
When I raced my Triton 500, I tried lots of things to get it to handle. I could ride it quickly, but never as fast in corners as the Seeley 850. I don't usually get involved in drag races down long straights. Neutral handling bikes are often committed to doing that.
 
WZ507 said:
To be clear, Web makes a 312 cam that is analogous to a stock Commando cam and they make the 312a that is considerably more cam than the 312. The performance cam that COMNOZ would recommend is the 312a. The attached plot is something COMNOZ posted here years ago.
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He has switched his fuel injected big valve 924 back to the stock profile cam.
Apparently that gives the strongest midrange power of all the available profiles. It will also be the easiest on valve gear.
It says a lot about Doug Hele's abilities that with all of the decades since and multiple attempts to get the magic cam profile for a hot road going Norton twin, for both durability and good road performance, Doug Hele had already drawn the thing in 1960.

Glen
 
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Just for the heck of it, some back on topic drivel.

There is no uncontrollable hit in power developed using a 2S cam. The cam comes into a range at 4000 RPM and up where it seems to work optimally, but it's far from uncontrollable in an old 750 twin. I doubt it would be that much different in an old 850 twin, but I've never ridden one. The lack of torque in the wrong gear never bothered me. When I used the 2S I rode in a gear where the engine sounded good and made usable power at the speed I was traveling at. Probably doing it all wrong. :rolleyes:
 
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