Dyno testing at work we did a comparison, m1 then the air gap made 15hp over the m1 and the indy made 25 more then the m1. Testing was done on a 360, 12.8:1 mech cam, w2 heads and 650 carb. Class engine and that was the carb that needed to be used. 525hp with m1 550hp with indy, just for fun we put a 850 on it and it made 600hp +.
Trevor
