Squish is to loose. I would like to see it at around .045 to .055. With 17cc domes you should have way more compression than that. The thing prolly runs like poo right now huh....... If I had to guess I would say you have to thick of a base gasket on right now. I dont remember anymore but I think the 421's are supposed to have a real thin base gasket like .012 or something like that.