This AVL job is a little different than the Iron Barrel Fireball.
It leans a bit harder on compression and combustion efficiency, and a little bit less on air flow. We accentuated the strengths of this somewhat more modern head design, as compared to the different strengths of the vintage Iron Barrel head.
It was a very interesting exercise, and a lot was learned because we were not afraid to push the envelope. And now, the performance envelope for the AVL extends somewhat further than previously thought
I think for higher rpms than 6000, or for 535 displacement, more flow from higher lift would be appropriate. But, for a 500 with mods only in the head/intake/exhaust, and nothing down below, it is quite a bump, especially in the torque department. I should think that this will be popular, partly because it is an easy install, basically just a head swap.
Based on reasonable estimation criteria of a 15% compression increase yielding 15% torque increase, and that there is enough breathing to get to 6000 rpm, we can calculate thus:
28.75 × 6000/5252 = 32.84 hp at the crank.
For 6500 rpm it might be more like 35 hp at the crank.
And if the breathing adds more torque than just the 15% compression increase , then the hp will also be higher yet. Depending on the rpm and torque figures, we may be looking at anywhere from 10-15 peak hp increase.
So, those would be some rational estimates which are probably in the ballpark. More would be possible with cams and/or ratio rockers.