Crane cams literature from years ago stated that moving the cam 2° would change the power band 50 rpm. Advancing the cam would peak it 50 rpm lower and retarding it 2° would raise the peak power 50 rpm. They probably knew what they were talking about, so unless you need to make more power lower or later for your combination or you are looking to operate the engine in a specific rpm range you will never notice the difference.
And that test was specific to that engine with that cam. You really cannot extrapolate much from that test. Engine Masters did a similar test.
