piston to head clerance

[dirty dan]

What is the min; you know of ever used successfully without damage. ???is intended for large bore engines . but not limited to them. please specify Wich when replying thanks

[sanborn]

Piston to cylinder head clearance depends upon several things; rod stretch, piston growth, combustion heat, piston skirt clearance, piston skirt length.

Little limited, small bore(4.00"), low RPM engines can use deck clearance as close as .020" and never touch. The larger the bore, higher the RPM and hotter the chamber the more clearance needed.

For a large bore(4.375") engine, turning 8000 RPM with good billet rods, tight piston clearances(.0045"), on gas, you will need about .032" to .035" for the pistons to not touch the head. Try to use a long piston skirt, with a tall ring stack to eliminate as much piston rock as possible. You can run tighter clearances with methanol, gas ported pistons, and of course, an aluminum block.

[dirty dan]

Why an alum; block ? is there another reson other then heat transfer?

[DartGT66]

It will wxpand slightly more than an iron block, therefore the deck height will grow higher when warm. I have the same kind of experiences with the numbers as Sanborn.