another j head question

63dartman,
You check at the high point of the piston which in this case is the outer edge. As for the heads being this small use a .055 gasket and hopefully the piston is .090 or more in the hole, and if it is then this engine will fly as I did one a few years back and was one of the faster engines on pump gas. Mine was .105 in the hole and dished pistons and a .055 gasket I think that I came in around 9.8:1 or so, but I know I ran it on pump premium gas. My heads were 47 cc's.
With these heads and a zero deck piston and alcohol and a .040 gasket and look out, fun is just around the corner.