Vented gas cap question


Active Member
Jul 15, 2003
My buddy just picked up a 67 FB and is having all the symptoms of an unvented fuels system (stalls after running a bit, top of gas tank is collapsed) and according to the service manual, these systems were vented through the gas cap. The PO replaced the tank and sending unit and the cap that is on it looks new as well, but aftermarket. This is the cap that I believe is on there:

So my question is, how do you tell if a cap is vented or not? His cap has a rubber gasket on it and seems like it is sealed very tightly, so am guessing it is not vented. Before he orders a replacement, want to make sure he gets the right one.
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