I just recently rebuilt my 1978 pontiac firebird 350 motor. It was running good untill i noticed the breather was smoking on the left head. I was also leaking oil. I took the air cleaner off and dumb me realized i forgot to tighten down the intake manifold. Anyways i fixed the oil leak but the left head still smokes bad out of the breather but the other head doesn't, what could this be. Is this just oil burnoff? Thanks, Jim