‘71 Dart with 340 motor stalling problem

Oldmanmopar said

Sounds like you have a common 71 fuel vent problem. Drive it with the cap off . Make sure the vent line coming to the engine compartment on the passenger side is open. 71's have a none vented cap and a sealed vent system that ends on the breather cap on the passenger valve cover. I have seen these lines plugged. and or crimped shut. Or rotted through at the vent tube and clogged with rust.

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Oldmanmopar,

This was originally a slant 6 car that I did a motor swap on. When I did the swap, I removed the little black can that sat on passenger side of engine compartment. I assumed the 1/4” line that came off tank to the can was a vapor return line and not a vent line, so I put a cap on it. Is it a vent line? Should I leave it uncapped? I’ve researched the gas cap I have and it is definitely not original to a ‘71. Someone has replaced the original with a ‘72-‘73 cap and obviously replaced filler neck as well. Assuming I probably do have a venting issue, but not sure how I should be set up to correct it. Tank has one barb that sits above sending unit which is connected to 1/4” line I referred to earlier (which I capped up in engine compartment). I don’t see any other way that I’m venting unless that ‘73-‘74 gas cap is vented.