Within Stock rules???

Originally Posted by Rick Leininger Jr.

Then why do all the newer combos (COPO, Cobra Jet, Drag Pak) go quicker when "gone through"?

So modified heads are the only way to make power? The engines are not sold completely blueprinted it is still a manufactured product. it's made like that so owners/engine builders can finish the engine anyway they see fit within the rules. Same thing that has been happening since the early 60's

There is no other way to improve a combo? Tuning, testing ect? Just do the heads and let it rip?