Re: Fuel Cap

Posted by TxGoat On 2024/4/10 9:58:19

Modern pressure/vacuum type gas caps are not suited for use on vehicles made prior to about 1972. Earlier vehicles use a vented gas cap in almost all cases. While some modern-type caps may fit, they will likely cause problems similar to what an original cap with a clogged vent will cause.

(It may now be illegal to manufacture or import vented fuel caps here in the Land of the Free)

Older model gas tanks are not designed to hold any significant pressure or vacuum, and old style fuel pumps mounted on the engine will not perform as they should if the gas tank is under any negative pressure. One solution would be to add a vent to an old tank. This would need to be done with care to prevent problems with contaminants entering the tank, and to prevent gasoline from being expelled from the tank under some conditions, and to avoid any chance of allowing gasoline vapor to enter the car body, including the trunk area. Attaching a 3/8 fitting and hose to the upper part of the fill pipe and capping it with a larger style inline filter gas filter and outlet hose might be a good solution, at least on older models. Avoiding dust and road splash at the vent exit would be a must, and the exit would need to be kept as high as practical. Drilling out or otherwise defeating the pressure/vacuum mechanism in a modern style cap might be easier, but that would also need to be done carefully to avoid problems with contaminants or water being able to get into the tank or with gasoline splashing out when making turns with a full gas tank.