whenever I remove the gas cap on my '73 4.5 in the summer, there is a release of pressure. I know the tank has a charcoal filtering device, but I am unsure if it is supposed to be under pressure, or whether something in the filter system is blocked. Thanks to anyone who knows the answer.

Everything is fine.it is a pressure cap like you would have on your cooling system. if you didn't have a pressure cap it would be hard to draw fuel from the tank. it keeps pressure on the fuel or is its like pushing it down or holding it down so the pump can pump good.

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Jake

93 300E 2.8L
72 Chevy Nova
74 Chevy Nova Custom W/Corvette Motor 70K