Im leaning towards a .060 thick gasket and machining the pistons down .020. I too have the means to do it myself. In theory It should give me .040 quench. Im only finding readily available gaskets in a 4.080 bore.
If you machine the pistons down .020 and use a .060 thick gasket you lose .020 valve clearance.
If you use an .080 thick gasket and leave the pistons alone you keep that extra .020 of valve clearance in case you need it later.
Both ways end up with same piston to head clearance, and both are equally correct procedures. But thicker gaskets cost about the same as thinner ones, so using the thicker gaskets is cheaper and easier. Both ways need the gasket ordered larger than block bore diameter. A 4.04 bore block uses 4.07 or larger gasket bore. The gaskets are actual size, not correct size for the diameter listed. A 4.04 gasket will likely overhang a 4.04 cylinder bore.
Call these guys and discuss the gaskets. They are a Cometic dealer and will help you get what you need. FBO Ignition - Home of the HRR688
