I'm having problems with a vacuum in my gas tank that's not allowing fuel to the carb. When I open my gas cap, its sucking in air. Does anyone know where to get vented gas caps for '72 Cuda 340? I found one place online, but shipping is more than the gas cap
Thanks.
Like most have pointed out, it is not supposed to be vented. It is supposed to be a "pressure vacuum" cap like said above. It is only designed to vent in or out in a malfunction of the vent system to keep the tank from rupturing. It does not vent enough to drive the car on.
And it is normal and preferred to have a slight vacuum or pressure when you remove the cap. It might be a vacuum or it could be pressure too. Either way it is normal.
You don't want the cap to be vented because then you may be able to smell gas in your garage when parked and the temps change and the cap will leak when the tank is full and you accelerate.
I am sure you have another fuel delivery problem and I can be sure it is a restriction on the suction side of your fuel pump.
Easy to rule out a non vented fuel cap, just remove it temporary if things are not working right or loosen it.
And a 3/32" hole is not enough to vent a fuel tank, if it appears it is then your tank is venting else where also. Is a 3/32 steam of fuel enough to keep your engine running at highway speeds?...No.
The vent should run up front to the your engine compartment and terminate on top of the engine. It can be hooked to the valve cover breather, to a charcoal canister, to the air cleaner housing or to nothing at all, just up on top of the engine.
My 74 E body has had the vent line open up on top of the engine now for years and I driven the car a lot and have driven it very hard and long out at Bonneville salt flats. The ultimate fuel delivery test.
This is my factory vent line with the rubber hose on it the keep it off the alt. It normally goes from here to the air filter and charcoal canister. I was gonna connect it to my air filter housing and never got around to it. It does not smell here as the gas fumes are heavy and stay down inside the line for the most part. Important to terminate the vent line on top of the engine. Not saying this good just that has worked for over 10K miles for me. It is how your 72 would be run.