Fuel return line

[340SHAKER]

Good morning all, This is a 71 340, do I need a fuel return line or can I get by with only the supply line? The car was apart when I purchased it so I don't know if the return was connected or not. By the looks of it I don't think it was. I don't even know what it should connect to. I am going to use a Thermoquad whereas the previous owner had a Holley installed. Thanks again for the help.

 

[Adam]

Yes, you can get by with it, as long as you have a vented gas cap. You may smell gas in the garage all the time. Usually the return line is for vapor and connects to the passenger side of the gas tank.

Thermoquads are good carbs, but sometimes the jet wells in the main body crack or separate along the bottom. If this happens it will run way too rich; you will have to replace the main body.

 

[340SHAKER]

Thank you. What should the other end of the steel line connect to in the engine bay?

 

[Adam]

Depends, on a 71, I think it was a connected to a nipple on the valve cover breather, or a three nipple vapor separator. Later cars had a charcoal canister.

Do a search for 71 Mopar fuel vapor diagram, or ECS (evap control system) & fuel vapor separator. Basically, they didn’t want the fumes venting to the atmosphere.

 

[340SHAKER]

OK, great. Thanks.

 

[340SHAKER]

I decided I would install the vapor lines. Thanks for the advice.