i have a 1984, it has a 302 bored .020 over, victor jr heads, intake and a holley 650. my question is: why would i have pressure in my fuel tank?? i put on a holley electric fuel pump with 3/8 fuel line. the pressure is enouph to blow the cap about 2 feet away from the car, when i hit the last thread on the cap. i have heard of a vaccum but not pressure. Please help me out, getting ready to sell it and buy a chevy.

 

Maybe you need a vented gas cap.