..............................Sigh................................
OP: Suggest you go over to MyMopar and download a free 73 service manual, and read and find out how the vent originally worked
Then download a 69 manual and find out how THOSE worked.
Then download a 70-71 manual and not the differences between those and your 73.
You say you have a "vented" cap. Are you sure? Or do you have the factory "pressure vacuum" cap which is NOT truly vented, but rather for pressure relief under both pressure and vacuum.
You can pull the cap immediately after a drive and see if there is vacuum in the tank
Be careful. The easiest way, if the smog stuff was intact, would be to leave the original 1/4" vent going up to the engine bay "open" up HIGH in the bay to prevent siphon. Others have suggested plumbing that line into the air filter bonnet to prevent smell.
By removing/ plugging "stuff" you can easily end up with a non-vent situation.
I DO NOT LIKE VENTED CAPS!!! The 69/ earlier were sealed, and the vent in the filler worked GREAT
The tank vent DOES NOT HAVE anything to do with filling the tank. That is done by the baffle in the filler tube.
