73 Charger - Vapor Separator?

[Hilljack68]

There's a brass shuttle valve in there that keeps fuel from flowing the wrong way.
It can stick.
If it doesn't rattle, it's stuck.

As I was getting the mower out of the barn (uughh, it's that time of year again), I gave the separator a shake... it rattles!

 

[multimopes]

(Is that the only difference between the '72 and '73?)

Not Sure, my car is kind of an abortion, and I don't have all of the specks and details of who did what. I also had a leaky fuel sender from the tank; so, while I had it up on blocks, I decided I wanted a stainless-steel sender. I got one from Summit Racing. Unfortunately, they only had one in 3/8" instead of 5/16". Then, I had trouble getting a hose adapter. I didn't want to use a coupling & threaded adapter, so I ended up ordering a double barbed, one-piece brass 3/8" x 5/16" from a marine supply as even searching on multiple Autopart's &/or racing suppliers yielded nothing. The next issue was that the stainless-steel lock ring was too thin to seal at the tank. I ended up using the original steel lock ring and all was well. Nuthin like fun N"Games!

 

[68BabyBlue]

(Is that the only difference between the '72 and '73?)

Not Sure, my car is kind of an abortion, and I don't have all of the specks and details of who did what. I also had a leaky fuel sender from the tank; so, while I had it up on blocks, I decided I wanted a stainless-steel sender. I got one from Summit Racing. Unfortunately, they only had one in 3/8" instead of 5/16". Then, I had trouble getting a hose adapter. I didn't want to use a coupling & threaded adapter, so I ended up ordering a double barbed, one-piece brass 3/8" x 5/16" from a marine supply as even searching on multiple Autopart's &/or racing suppliers yielded nothing. The next issue was that the stainless-steel lock ring was too thin to seal at the tank. I ended up using the original steel lock ring and all was well. Nuthin like fun N"Games!

I used that same double barb in a different setting, joining different sized air lines to run the pneumatic vibrators I used to unload sticky material from the bulk tankers I used to pull. I bought them in the plumbing supply section of Lowe's and Home Depot.

 

[72 charger]

On my 72 charger I couldn't tell if mine was any good or not and didn't have much luck at the time finding one so I ended up taking fuel hose and looping from one nipple back to the other for all 4 and bought a vented gas cap. I don't believe it has caused me any issues. Sometimes I wonder if I should run them out somewhere higher for vents as the only vent for the tank is through the cap then.

 

[multimopes]

In your case, at least the Dodges had the filler neck projecting upwards through the rear quarter panel. On the Plymouth models, (like mine), the filler neck is much lower, behind the rear license plate.
Venting there would present more of a problem. Not to mention, fueling up these days with newer type of sliding nozzle, it's a pain in the ars to fill as it want's to puke out some gas when nearing the end of pumping & trying to "top it off"!

 

[Hilljack68]

The next issue was that the stainless-steel lock ring was too thin to seal at the tank. I ended up using the original steel lock ring and all was well.

I had the same issue on the aftermarket tank and ring on my 68. The ring was too thin, and I had to by a factory ring off one of the guys here on the forum. It fit like a glove!