stock valves vs. aftermarket

i'm rebuilding my 420a. whats the difference between expensive valves and stock ones? is any power goin gto be gained with the more expensive ones?

Hey bud, first of all this one should be under the Performance section of the forum. i personally want to rebuild my head also, not for fun but cause i need to. Anyway look on there and there are like 3 other threads on this subject IIRRC.

Unless you are going to be running nitrous or a lot of boost I dont think its necessary. Even then, I dont know exactly how needed they are.