[AROWHED]

I've always struggled with fuel cap and filler neck vent line spillage and gas tank pressure with the 65 GP. Every vented aftermarket fuel cap I have tried leaked to some degree, and gas always came sloshing out the factory vent line even under moderate acceleration. I think modern gas blended for fuel injection is very quick to atomize and build pressure, more than the vent systems were designed for with 1960s fuel.

So currently my setup is a GM factory nonvented cap with the vent nipple on filler neck welded closed...so at least no more fuel-stained license plate and rear bumper. I welded a 3/8 steel vent line through the fuel level sending unit assembly. It connects to a large steel can fuel filter that is postioned vertically, also it is above the tank and rear axle, the idea was it would act as a liquid\air seperator for fuel thats getting pushed up the vent line. From there I used the original 3/8 fuel line along the frame as a vent line, where it terminates inside the engine air cleaner to capture and burn gas fumes. (No mechanical pump, car has an electric pump, return regulator, and separate delivery\return lines ran along passenger side.)

Unfortunately this venting method does not work if tank is more than half full, liquid fuel still gets pushed up through the inline vertical filter (which I bet can hold 1 liquid cup itself), and further up the line until it spills into the air cleaner. Every time i get out of the car, I can catch a whiff of gas, and the fuel tank is under a small degree of pressure until I slowly open the gas cap. I have used compressed air to check this vent line for restriction but it seems to flow freely.

I would like to know how others have addressed their problems of fuel spillage, and excessive fuel tank pressure.