440 heads.....
I recently bought a 72 440 HP block that is bored .030 over and a set of 346 heads. The reason I purchased these heads instead of the 906 or even the 915 is because of the fact they have hardened seats in them for unleaded gas and the fact that they have a cooling chamber around the spark plug. This is a street car and with the better cooling and the right seats, I figured this was a good way to go. I know I can get more horses out of a set of 915 heads because they are closed chamber heads, but what about availability, they are hard to find. My question is, how much of a performance difference is there between the 906 heads and the 346 heads? What about horsepower difference?