I figured the comp. would probably be a little less than 10.6 because I didn't know what cc the valve releifs were so I just figured it with none. I was just trying to get a ballpark idea for now. The heads can only be cut to 62cc's I think, so maybe I will cut them to 68cc;s and moc the engine up with checking springs and check the valve clearance. Then I can order thicker or hopefully thinner gaskets. I think Cometic makes some .027 gaskets. This short block has ben in 3 different cars in the last 15 years. I've run a 312/590 and a 324/650 cam in it, both with 1.6 rockers and had plenty of clearance. This engine has also seen a LOT of NOS over these years. The car it is in now has a 350hp fogger on it. Years ago everyone said to run low comp. with NOS, but now that seems not to be true. Just about everthing that I have always been told to do in a engine is the wrong thing to do now