I just put a new crate engine in my 70 chevy truck. It's a Gm 350 HO with a Holley 770 carb. I'm getting gas in my oil. Both GM and Holley say the carb is not too big. So it isn't the carb pushing too much gas into the engine. The guy from Holley asked if I had a vented gas cap. I did put a new locking gas cap on and I'm pretty sure it's not vented. He said all 70's had vented gas caps to prevent too much pressure building up in the tank. he also said that the pressure builds up and when the engine is shut off it continues to push fuel into the engine which ends up bleeding over? the rings and into the oil. Does this make sense?