I bought the Nov issue of Hot Rod Deluxe for the Yblock build-up article. They show dyno charts for the same engine with two size carbs and with and without headers and a step-up the the Blue Thunder manifolds. Unfortunately the dyno charts start at 3000 RPM and they do not give the compression ratio of the engine or a manifold vacuum value. The TAKE AWAY for me was going from a 465CFM Hollry to a 710CFM Holley gave SIGNIFICANT IMPROVEMENT at 3000 RPM and up. All of you that keep repeating advice of using a 390CFM Holley should read this article. If you have a performance cam then if you don`t use a carb that will support it, you are wasting your money. AS always my opinion. Pete