Comsidering all 12 port heads what is the approximate HP gain by using one? Raw numbers? percentages? I'm talking actual street HP for a GMC, the 261 and the 292. I'm wondering what it would be for a non temperamental, regular hot rod motor for the street, not something you always gotta tune and mess with to get it right so you can drive it to the next rod run.
Anyone with any thoughts?
