IMO, it can be argued a stone stock engine with a good tune (distributor curve kit and limiting total timing) makes an HP engine. Certainly if you add a 4 barrel and some headers and certainly if you optimize the camshaft timing using a compression gauge. Between "all that", I think close to an honest 50 or possibly a little more HP might be added, depending on "how bad" or how "emissions leaned" the tune was to begin with. I've DONE IT several time and I can tell you first hand they all went from not even squeaking tires to literally broiling the hides. A car that can lay two rubber strips through second gear from a dead stop doesn't have an "HP" engine? Horse hockey.