Have a question: My '69 (originally 307)has just a fuel line, no vent. It's a 3/8" line. I bought a repro sending unit and didn't notice until I got it home that it had a vent line. Any problem just attaching a vent line to it and venting it somewhere in the back underneath? Thanks.

Noel

HI Noel, my car came with the dual lines, but one of my lines is capped with piece of hose and clamp and a bolt in the hose and clamped, when someone used a single line fuel filter. I bought the double line filter and have the 2 line sending unit, but still have it capped off and my engine runs fine. Its meant to help cure vapor lock by returning unspent fuel to the tank but seems to work fine without it attached.
That dual line sending unit is getting more valuable too. harder to find these days it seems.

You will find the return fuel line most often on cars equipped with A/C. A good thing to have if you plan on running headers.

Thanks for the replies! The car was a factory A/C car. But there were no return lines when I bought it. As far as I know it was an untouched original. I think the fuel and return lines ran parallel from the factory. The fuel line clips on my car are only the single ones. If I decided to run the return line, does it juct run from the backside of the fuel rail at the carb? Thanks.
Noel

The return line ran from the fuel filter on the front of the engine (between fuel pump and carb) back to the tank. From everything I have read, this setup was on the L48 350 cars and the L35/L34 396 cars. Something about the fuel filter serving as a supplemental fuel reservoir on the Q-Jet-equipped engines.

So, with the right 3 piece line kit and filter, you could run the dual lines on any engine except the 6.

I'd most likely swap the dual line sending unit out for a single line unit, but that's me.

The return line ran from the fuel filter on the front of the engine (between fuel pump and carb) back to the tank. From everything I have read, this setup was on the L48 350 cars and the L35/L34 396 cars. Something about the fuel filter s

As eric points out the only '69's to get the fuel return line are the LM1 (350ci/255hp), the L48 (350ci/300hp) and the L35 and L34 (396ci/325&350hp) equipped cars. I don't think it had anything to do with air conditioning.

I believe (could be wrong on this) that all single line cars gas tanks were vented with a line that stayed back by the tank and used a non vented cap.

The LM1 engines also had the dual lines setup as they used the Roch. 4 barrel setup. You can see the filter in this pic with the return line making a sharp U turn down and back to the return line on the frame below the fuel pump.
http://www.brainerd.net/~knudsen/69RS/UnderHood/350wRoch202aa.JPG

I may wrong on the 69 Camaro, but I do know my 70 Chevelle has a return line off the fuel pump and the car has A/C. This was put there to deal with the vapor lock condition caused by the extra engine compartment heat generated by the A/C.

gmranch, Im sure the a/c added heat to the area but from what Ive seen in LM1's and guessing the other engine configurations as well, that they all had the dual lines with or without a/c, it had more to do with the 4 barrel setup and vapor lock issues. Surely a/c made the problem worse but non a/c cars also had the setup with the 4 barrel Roch. carbs.
Ive seen quite a few pics of dual lines over the last 2 years here, and about half were non a/c cars.
Its always fun to try to get into the heads of the designers from 35 years ago and wonder what their logic was then. smile.gif

Yes, I've seen some of their amazing "logic" too. smile.gif