Re: Fuel Cap

Posted by TxGoat On 2024/4/10 10:01:28

I use a cap like the one on the right (low pressure) on a 1972 Ford pickup, and it definitely causes some pressurization. As I recall, it had a label of some sort attached to the flattened area at the center of the chrome cap.
While it requires very little vacuum to open the vent, it requires significant pressure open it, and when it opens, it makes a honking sound. The '72 Ford pickup cap does fit my '37 Packard, and looks similar to the original. Putting a pressure/vacuum cap on a car in storage might help keep condensation out of the tank and prevent decay of ethanol-adulterated gasoline. I'd prefer an original type cap, but the low pressure type cap ought to work, and they do have a good gasket that is not affected by ethanol. ANY restriction that can cause negative pressure in the tank will aggravate issues with fuel delivery, especially in hot weather, and any pressure cycling of an old tank could aggravate any tendency to leak. With a sound tank, some mild over pressure should not cause any problems, and it could help with vapor lock problems in hot weather.