If i throw a set of 243s on my stock 5.7 bottom end what will the hp gain be if i get them milled so the cc size is the same?

 

probably anywhere from 15ish-30ish hp.. but im not a dyno

 

well im asking that just to get a start i am going to add more stuff than whats in my sig like
1 7/8 LTS, lS2 intake, 90MM TB, TSP 100mm Lid (when it comes out lol j/k)
Small Cam, and going to mill the crap out of heads....hoping for 420hp area after tune.