I just recently acquired a 1950 Chevy 3100 and I replaced the gas cap with a new one from LMC because the one on the truck was dented and the rubber seal was disintegrating.
However, now when I remove the gas cap, there is a loud pressurized sound - not sure if it sucking air in or pushing air out. I could understand there being a little bit of pressure in the tank, but I am concerned that it is a lot of pressure. Is there supposed to be some sort of tank vent? The old gas cap didn't have anything built into it, but the new one looks like it has some sort plastic vent thing in the middle inside.
