1971 Mustang Gas Cap

I searched but couldn't find specific info concerning the D1ZX 1971 gas cap.

Does anybody definitely know if it is vented? I need an OEM vented cap, I also have a 1972 D2ZX NOS OEM cap. I don't want to keep both, just the vented one.

TIA.

I had a disagreement about this issue in the past. I will tell you what I found. The gas cap on my 72 has a rubber gasket and a small hole in the center of the inside of the cap. When the cap was tested by the DMV inspector I was told the cap doesnt hold a vacuum. When the DMV checked on their computer, it showed 1972 gas caps did not hold vacuum and my car passed. Is this a vented cap? Seems to be matter of opinion. Our gas tanks ARE vented because I have changed my tank...and cleaned the tank mounted hole cover and the hose to the chacoal canister which is in the engine compartment. So when fumes coming out of a half full tank on a summer day they go thru the tank vent hose. And the fume canister has an additional hose that goes to the air filter housing thus drawing fumes into the engine and creating a slight vac in the gas tank. But, air is allowed to enter the tank through the gas cap to prevent air lock. So is it a vented cap? It is a cap for a vented tank, that is the reality.

My gas cap vented.

mike