what size cam???

Big cams have needs. Compression, gearing, converter if you have an automatic. That's just a start. Over camming can often give you a car that performs worse than stock. The only way to reply to your question is if you give us very detailed information on your car set up, intended driving style, and stats on the engine the cam will be going in.

Really, with the info you have given its impossible to give you an answer.