If you use that formula with your size motors C.I. then it gets harder to make 2.0 HP per C.I. My pump gas 518 C,I. street stroker motor made a best of 775 HP with a set of CNC ported 440-1 heads that flowed 370 CFM, my 526 C.I. race gas bracket motor with the same heads and carb. made 845 HP missing due to the header flanges being to small for those heads It might have made another 5 to 20 HP , not near enough to get 2.0 HP per C.I.
I've built and dyno tested several roots blown 426 Street Hemi type motors that both made over 2.0 HP per C.I. at or above 10 lbs. of boost