Flip fuel cap on Duster need to be vented?

Just bought a flip top gas cap to put on my 1972 Duster. I bought a delrin adapter, and installing it is not the question, but rather function. The current standard cap on my a Duster is clearly vented, and my new to me flip top gas cap is not vented (smooth version, not the version marked “FUEL”). If I install a non vented flip top gas cap on my Duster will I be creating a new problem because it’s not vented?