quote:Originally posted by PanteraDoug:
The procedure for determining piston to valve clearances is a standard/known procedure.
You don't calculate it, you measure it with clay.
For safety a "standard" number is used. I think it is .080" on the intake, .100" on the exhaust.
US pistons are all made with those considerations and you don't get close until you are around .650" lift.
So that really puts the "Pro Stock" and NASCAR type engines in danger with .700+ lifts.
And I tried to "refocus":
quote:Originally posted by René #4406:
I do'nt agree, the minimum clearance may occur a bit before or a little after the top dead center, I checked it on other engines where I was using a camshaft with a lot of overlap and very fast openings and closures.
Anyway, I never asked how to check that, I know how to do it, I just said that having the lift curve facilitates this check.
My subject was above all the supply of lift curves by cam grinders in order to really compare camshafts with each other.
But George agrees with me, we have to check a bit before and a little after the top dead center, not just at the top dead center.
George, do you know why cam grinders usually refuse to communicate the lift curves?