My heads are cut .100 to make 452 heads closed chamber. I have access to machinery... or I did. Im to cheap to replace pistons and deck the block. I do it cause they say it cant be done. I also made my own cut to fit push rods. It just sounds like the oil pump is bad when you rev it up and the lifters rattle... I guess I can tell the chevy guys my cam is wiped while they see my tial lights and smell my tires.