My 72 Challenger project is in the "shell" stage with sheetmetal work coming to an end. So basically the fuel system is completely out of the car at this time.
The car came with the gas tank that had the vent tube in the trunk and the tank with the 4 nipples.
I plan to put a big block in the car. It will be streetable and hit the strip from time to time. I would like to get into the upper 10's with it.
I don't want to put a fuel cell in the car.
My question is should I ditch the vent system?
Any suggestions on a good setup?

You should have some kind of vent system to prevent pressure/vacuum from building up in the tank.

You could go the way of the 70 non ecs and run a vent line from the top of the filler neck to inside the frame rail. Simple and may save about a pound.

But that pound would be over the rear tire so it would be a wash in my opinion.

My '72 'Cuda came with the same setup. When I got the car the gas in the tank was more like molasses than fuel. Even after a thorough cleaning I wasn't all that confident in the vent system so I plugged the four factory ones and ran a 1/4 in. line from the filler pipe in the trunk to the frame rail as someone else suggested. Works fine and I don't really notice any gas fumes. I also have a 3/8 in. sending unit with a return line fitting. I run a 1/4 in. line from the fuel block back to the return line fitting on the sending unit. I put a .040-.050 restriction in the return line.

This is what those 4 lines hook up to.
it sticks up in the trunk, there's nothing wrong with it, use it.



3 lines going to the front, I get them pre bent from Fine Lines, easy as heck to install.

2 lines go to the sending unit and the third connects to the rear vapor separator.

Sending unit hookup.

Your 72 should have this(read down below) style gas tank in it, maybe you have the wrong tank for your year car?

I just did the same install on my 74 challenger a few weeks ago and have driven the car over 500 miles since. Having a return even with a stock fuel pump helps a ton with todays gas. I use the factory hemi VS in front bolted to the fuel pump with a #57 nytrous jet stuck in the return fitting because the VS I have has a #42 hole in it.

I used a vapor line for a 74 so it was right for that year car.
But the other lines(suction and return)are for a 70 or 71 hemi or 440/6pak challenger which get's you the good stuff. I got hemi challenger parts on my 74 challenger!!





Put some spark plug wire heat sheild around the lines up next to the front frame rail by the engine, it's clamped to the frame rail.

This setup will insure your ready for a electric fuel too with a return. Return is where it's at nowadays, I'm telling you. The vent line goes up and connects to the crankcase of your engine, usually through the valve cover breather, that's the best way. And if you eliminate using those 4 nipples your car fuel tank will not be vented when the car is parked out of level in some cases. It's the wrong way to vent your gas tank with one nipple.


Here's my car running 2 nighta ago.
web page

Very early 72's used the big vent tube in the trunk just like the 71's. I'm not sure exacly when they went to the small vapor separator on the shock x-member. It had to have been very early in 72 production.

Thanks for everyones help!

I cut the top of my 1971 Duster gas tank off, those same four lines allow gas to fill up all the way into the top corners Take a mechanics mirror and light and look at yours through the filler neck Don't block them off if you want a full tank

Avgas is equally good for long term storage.

The tank/vapor separator changes for the E-body, as with the B-body, are described as “after March ‘72” in the parts cat. I interrupt that as production dates April 1, 1972 and later. Appears there were fuel tank/vapor separator changes on other platforms as well. The B-body filler neck and gas caps changed on April 1st as well, moving to the safety catch cap.

so how does that junction box in between the shocks on the crossmember vent? My friends 72 satellite has a new tank and is equipped with that junction box and we are having a vacuum problem with the tank,car is running out of fuel and when you twist the cap off a huge rush of air sucks in..........
yep im bringing this super old thread back from the dead :-)

Basically the Junction box is the 4 vent lines going in the bottom with a vent tube going out the top and up to the Charcoal Canister in the engine compartment.

Excess fuel that gets into the box should work it's way back into the tank through one of the 4 vent line and vapor goes up to the charcoal canister.

I am not sure if there is an orifice or check valve in there.

If you remove it, air should go in each of the 4 lower tubes and some should come out the top. If it's clogged try soaking it in Carb Cleaner.




Yes and no.

It was not meant for filling the tank but by simple physics if the tank is parked in any position other than filler neck higher than the rest of the tank, It will trap air in the tank if they are plugged. Not it's purpose but it will have an effect.

There is a check valve inside the vapor canisters. It's probably all rusted up inside and won't vent. Remove it and soak it in EvapoRust to clean the inside. Once it's clean, you should be able to block all but one of the four inlet nipples, then suck/blow through the output nipple and feel the valve working. The valve will only allow air flow in the middle of it's travel. If you suck/blow too hard, the valve will seat and not vent.