Megacycle Cam clearance....
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Fast Eddie
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You mean “with Maney steel pushrods AND an alloy barrel” ?
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With iron barrel and std alloy pushrods , the recommended running clearances are 0.13 both inlet /exh, (checked on Old brits).
Yes indeed. Lack pf detail. Doesn't everybody have Maney alloy barrels?
Not necessarily, it depends on the specified clearance. The barrel doesn't expand at different rates to suit each cam
The cam has nothing to do with expansion of the barrels.
Stop twisting things, different cams have different clearances (you do realise that?) My full race cams use 8/10thou, so I set clearances at 2 and 4 thou
Maybe you should measure the expansion rate of the barrel and pushrods to see how much they grow by
So, the setting for a cam with 8/10 would be different from a cam with 16thou
I just followed Steve Maney's recommendation. So, argue with him jf you must.
I have known Steve for over 30 years
The recommendation is for his cams, but the barrel/ steel pushrod combo grows by approx 6 thou
Other cams specify 16thou clearance.........
What cam are you using?
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I check the tappet clearances when the motor is hot and set them at 2 and 4. Altering the clearances alters the cam timing equally at both ends of the duration. The closer the clearances are - usually the better the timing. If you use methanol fuel, the motor does not get as hot as it does with petrol. If I was using aluminium barrels, I'd have difficulty getting enough heat into the motor. With petrol, I'd sett the clearances a little wide, then ride the bike until the motor was really hot, then reset the clearances closer. It is what works which is important -not the theory.
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What you need to be careful of are 'ramp cams'. Quietening ramps confuse the issue. They usually run with wider clearances. But I have even run those close.
Another consideration is the type of head gasket. If it settles, the clearances might become reduced and the valves might not seat properly. The specified clearances are probably worst case scenario.
Another consideration is the type of head gasket. If it settles, the clearances might become reduced and the valves might not seat properly. The specified clearances are probably worst case scenario.
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I doubt that that the cam manufacturers specify a lash clearance capriciously. I am not a cam expert, but it stands to reason that lash setting determines when and where the tappet makes contact with the cam's profile which then defines the point where the cam begins accelerating and ends it's decelerating.
I can also understand that a builder who employs a barrel and/or pushrods made from material different from "stock" will probably cause the builder to alter the lash settings.
If, like me, you are not an expert in camology I suggest following the manufacturers instructions. If you choose to venture into this area without anything more than good intentions I suggest that you seek advice from someone who is an expert before your good intentions turn into good riddance.
Best.
I can also understand that a builder who employs a barrel and/or pushrods made from material different from "stock" will probably cause the builder to alter the lash settings.
If, like me, you are not an expert in camology I suggest following the manufacturers instructions. If you choose to venture into this area without anything more than good intentions I suggest that you seek advice from someone who is an expert before your good intentions turn into good riddance.
Best.
What theory? The ally barrel grows by 6 thou. Reduce your clearnace by 6 thou and you will be correct
Different cams have different ramps. A 4S is spec'd at 16thou clearance, a standard one isn't
My grandmother already knows how to suck eggs
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