I had two sets of Indy heads with Max Wedge ports, CNC 440-1 and a set of Max Wedge SR heads, there was 50 HP differences on my old pump gas Duster motor on the same dyno the same day.
There was 65 HP difference on the 526 C.I. race motor with higher compression and race gas Both sets of heads were either 75.0 or 76.0 CC, CRS No other changes, same cam, same compression ratio, same intake and carb. same ignition and timing. More air and fuel makes more power.