Quoting Edmund Villasana <edmundv@xxxxxxxxx>: > I'll check the heads when we pull them, but I have a question. What are > 915 > heads and why would it be good that I had them? (sorry, like I said, > I am > new to the world of Imperials and big blocks) > Eddie > Villasana > As Dick B. said, the later (906) heads had larger diameter exhaust valves (1.74 from 1.60, significant increase) and the intake ports may have been enlarged a bit more. As a result, the 906 should be better for upper end performance at the possible expense of some low speed throttle response. D^2