Dynamic valve clearance question

[73 Mike]

I've been following along with 69427's threads (yes, I have engine envy) and a question occured to me.

What really is a reasonable valve to piston clearance? The only "spec" that I've seen is .080 from Eric. It occurs to me that even if you do the clearance check with clay on a bolted up engine with soft springs you are not allowing for any dynamic "float" beyond the actual lift height. I presume this would only apply to the exhaust as the piston would be closer to BDC when any overshoot would occur in the intake valve.

Is .080 enough? Would it be spring pressure or valve lift dependant? Different for solid and or roller lifters?

Paranoid

 

[TimAT]

there's a bit in the old Chevy Power book about that. I'll dig it up next time I get home.

 

[mrvette]

I have a general engine design question.....for a street machine, one that is high performance and subjected to rather high rpm and abuse....much less granny's grocery getter....

why would any engineer EVER allow ANY engine to have ANY chance of the valves hitting the pistons???

under ANY circumstances???

to ME, it's a senseless risk of premature cat ass trophic failure....and a lousy design reputation as the result....