Fuel Supply System

[SlyGuy]

Making slow progress on my 72 Challenger build. Need some advice on fuel supply. Two things that I don't quite understand: First, is a fuel return line necessary? Second, proper venting of the tank.

The original tank that came out had the four hose connectors for the emissions I believe. My replacement tank, however, does NOT have any hose connectors. I think it is actually a replacement for '70 Challenger. My sender has a 3/8 hose connector, and a second smaller hose connector. I am going with mechanical fuel pump, and carb. I have the supply line ran from the sender to the engine compartment. The only other hose connector that I see is at the top of the filler neck just inside the quarter panel. So, what all do I still need to make this work?

Do I HAVE to run a return line to the second nipple on the sender, or can I use that nipple for venting, or can I simply cap it off and use the nipple at the top of the filler neck for venting?

[Brads70]

Nice carb!
You could use the nipple on the filler tube for a vent. Mine does not have that? Maybe because mine is a 1970 with CA emissions? Be warned the sending units are notorious for not reading right.
Yes you could use the smaller line on the sending unit as a return. What are you using for a fuel pump? Stock or Electric?  How " correct" are you trying to be or does that matter to you?
I'm not much of a purist....

Found these pictures for the internet....

Roseville moparts is a sponsor and give us a discount( just mention it when ordering)

https://www.rosevillemoparts.com/product/fuel-vapor-line-bulkhead-70-74-b_e-body/

https://www.rosevillemoparts.com/product/70-71-vapor-fuel-line-challenger-5_16-2pc-oe-steel/

[SlyGuy]

Thanks. The carb is a Quickfuel SQ-750 with an Edlebrock Air Gap intake. Sounds cool to say, just wish I understood all of this a little better lol. The engine is a junkyard 360 magnum. We did get lucky on the engine, as it turned out to be really clean inside and bored out .040 already. We still tore it down, sent it to the machine shop, and put new EngineQuest heads on it. It's been fired up once for break in, and sounded really good. I am a first timer to all this, and definitely NOT a purist. Honestly, just want it done and drivable.

Back to the fuel question. I am trying to build an old school muscle car that I can drive and have fun in. The fuel pump is mechanical, engine is carbureted, and I got the most basic fuel tank I could find (with none of the nipples for emissions stuff). Since I got a tank for an older model, should I have got a sender with only one line? I don't understand fuel return, and if I need it on my set up. and if so, what does it hook to up front? Thanks again.

[7212Mopar]

If you go to the resource section, you should be able to find the manual. You will see the 72 and 73 has an external "collector" that the tank vent to, one line will go to the engine bay charcoal canister. The charcoal canister I think connects back to the air cleaner. It sort of act as a vent. There is a diagram in the manual that illustrate that. If you no longer have the canister, then you don't need to run a line to the engine bay, unless you plan to have fuel injection in the future. If your tank is not a 72, 73 then no need for the canister. For the unused port at the sender, you can use a short piece of fuel hose and plug with a bolt inserted and tighten with hose clamps. The tank can be vented per the pictures post by Brad. I don't recall if there is difference between 72 and 73. Also, I have a locking gas cap and I drilled a 1/8" small hole in the rubber gasket to help vent the tank.

[Brads70]

I'd suggest mounting a fuel pressure regulator ( on firewall?) that has a return line on the firewall. Make a fuel line from fuel pump to regulator then reg to carb and a return line.
Benefit of a return line is it goes a long way preventing fuel boiling issues.
I have used   this website various time , plumbing up a few cars and a few stock cars over the years. Never had an issue.  Price is right too IMO.  https://www.frozenboost.com/index.php?cPath=219&osCsid=6dd5cc73b412f25e6949c519f71b64d3

[SlyGuy]

Thanks guys. I REALLY appreciate the input. I went ahead and used the rubber hose (with a bolt clamped in) to cap off the return nipple on the sender (thank you for that idea). I also procured (from Roseville), and installed, the vent tube kit that runs from the top of the filler neck down to the frame rail (thank you for that idea as well). I also installed a half inch phenolic spacer under the carb. My understanding is that should help to prevent fuel boiling?

The last piece of the puzzle (I think) is fuel pressure. I read the fine print on my carb, and it says that it needs 6.5 psi. I read the fine print on the mechanical fuel pump that I have, and it say that it supply's more like 8 psi I think. Not sure if that is a big enough difference to require a regulator or not. Wish me luck lol.