Dave, from what I have read on the subject, the space or clearance between the top flats of the piston and the flat of the head is called quench or squish and for best performance should be .050" but not less than that. My 292 is equipped with propane pistons for 9:1 compression in a stock engine. The block was decked about .030" which brought the piston tops at tdc .015" below the deck. With the advertised gasket crush thickness of .040" that gives me a clearance of .055". I allowed some extra so that any errors in my calculations would not get me below that magical .050" clearance. The head was milled just enought to true up the surface. Regards!
