Originally Posted by Not yr uncle Bob
Originally Posted by AndyF
Probably just need a vented gas cap for your make and model.


FWIW after some study I gave up and ordered a vented cap based on your advice, and this note in Ehrenberg's auction: Great upgrade for pre-'73 A-bodies: Two-way check valve solves tank venting problems forever. All vent lines on tank can be capped off!



That is exactly the type of cap that made my gas tank oil can as it heated up and cooled off. I'd pass on it, not to mention tha tif you have any kind of emissions inspections capping off the vent lines would likely fail the visual.