compression ??

The gasket should run about .039" or so if it is the common composite gasket. With the piston at top dead center, how far is it from the blocks deck, to the piston top? I see .204" mentioned, but that is a number I have never even seen close to on any I have measured. How are you getting your measurement? The bore size you know is .040" over, and we know the stroke. A good piston-deck measurement and we can give you a close guesstimate, assuming the 80 cc head measurment is accurate.