devwolf

When I first got my car, it was fine. Was about 10 years old, but it was running great and the body was outstanding. As the years went on, I would notice, every time I opened the tank to fill it, it would make a puff. As if it was venting pressure. By 2017, this was a 4 or 5 second long vent that would continue as I screwed off the the cap. I could literally see the fumes coming out of the tank, they make those heat wave shadow things on the car. I'm now rebuilding the whole car, including the engine, and going for a Pro-Flo 4 XT with the return style pump. Im worried that the return style and increased fuel usage (we are doing bore and stroke) will start to cause some rather dangerous pressures In the tank. Does anyone know why the tanks do this? I know there is a vent on the tank that tends to get old, but im not sure how it would be this badly plugged up; im hoping its the regulator because thats one of the parts that comes with my kit. If it is the vent, what have you guys done to replace them? Is there a place that sells OEM tank vents, or does anyone have the GM part number?

RBob

iTrader: (1)

Tank pressure is controlled by the canister purge vapor control valve. It is located near the canister inline with the hose that goes to the gas tank. It opens at a little under 1 psi to allow fumes from the tank to enter the canister.

The mushroom vent by the rear axle is mainly to allow air into the tank as the fuel is consumed. Although, if the CCP vapor valve gets clogged or stuck the mushroom vent will open at a pressure slightly higher then 1 psi.

RBob.