55 … from what you asked I was just saying what we did with another manufacturer and the gasket sizing. I would have started with that if I had thought of it as I didn’t think it mattered. My main reference was for the 2 mating surfaces are different for MLS gaskets than Felpro blue. I also wanted to show we lowered compression the gasket was .025” thicker. Cometic offers gaskets to .018” and a std Felpro blue is about .041 compressed. If an .018” was offered for the Y-block in the proper bore and I needed it, I would sure use them to raise compression…

56 Vic, B'Ville 200 MPH Club Member, So Cal.

AFIK the original shim head gasket is still available. It is .020.. I have had good luck with them

Although I'll be running iron heads (less movement), there's still the possibility that MLS head gaskets will require re-torquing. Ted prefers Best composite gaskets, but I've found that they are offered in just two bore sizes for Y, both of which would be greater than cylinder bore size + .030-.060 that Ted recommends. I know that I would like to avoid having to remove the rocker assemblies to access the head bolts, after the engine has been built and running.