i don't think its your vent i have tried it like that with no problem i also had it with just small hole drill in the cap. what you will find in the archives is flow check gals hour flow i cant remember but you will find that its in the achieves all have went to 3/8 line or better 3/8 i feel is plenty. also if you add a faucet type pump in line is wrong it has a check valve in the pump use this type for transfer only i was lucky it did not quit on me i was thinking it would give me redonece!!!!!!!!!!!!! wrong !!!!!!!!! also use the old universal fuel filter old mopar type of the 70s
mac