I have a problem with on of the bowls on my holley 700dp overflowing because of pressure in my fuel tank. I drove my car around yesterday some. I have the factory in-tank pump with mallory bypass regulator. I noticed after the car was shut off that fuel was still coming out of the lines. I opened the gas cap and it seemed like there was either pressure or vaccuum. After I relieved the pressure it stopped. Has anyone every had this problem?

 

What did you do with the charcoal vapor canister?

 

Unplugged and unbolted it. Should I plug up the vac line that went to it or leave it open?

 

The vacuum line goes to the engine. If you mean the line from the gas tank that goes to the canister, the best approach when there is no canister is cap the line and use a vented gas cap.

 

A "vented" gas cap will still allow the fuel tank to build about 1PSI of pressure before the valve opens (it uses a spring loaded valve). It's an emissions thing to reduce evaporative emissions, and it can cause fuel to be pushed out the fuel lines even when the car is turned off, although 1 PSI shouldn't normally cause the inlet valves on the carb to unseat.

Your stock gas cap is not vented but there is an equivalent pressure vent down by the tank behind the rear axle that performs the same function.

Take the vent line that comes from the tank to the charcoal canister and leave it open on the end. That should prevent ANY pressure from building up in the tank.