I got a motor and I don't think it's putting out the power it was suppose to. Is there a formula to get an idea of what I have. It's was suppose to be a zz502 that was rebuilt and the cam specs from what I was told is the same but this motor has square port heads and the zz's have oval port. I took the heads off when I got the motor and had them shaved 30's so I thought it would be around 10 to 1 comp. but I don't think it is. Just trying to find out what my comp. is and get an idea what my hp's are near so i can decide what to do.

Dyno I dont know. The thing with HP is getting that number is theory, yes they can get a number but even still HP is not a 100% accurate science.

well.. its not that easy. first question is " what are you using to make this judgement about the power you have or don't have ? dyno , guessing by looking, how the boat used to go vs what it does now ?

as a base line a zz502 should make 500 hp give or take. if you have upped the compression ratio a bit then it will make a bit more.

but having said that you are talking about somebody's rebuild here. if they did a good job mechanically and used the correct parts then you can expect to see those numbers. if they did a poor job mechanically then the numbers can be much much worse. bad ring baps, poor bore sizing and finish, bad valve job, mis set cam timing... the list goes on.

if you want to know the answer, go to the dyno and find out the answer. guesswork like this is a complete waste of time.