knighthawk

'69 Cutlass S , the gas tank has 2 lines comming out at LR corner, to a common vent. One is 1/4 and the other is maybe 3/8. Can I use ther 1/4'' line to run a return fuel line from the engine up front ? like from the fuel filter bypass ? Do both lines at the tank need to used as the vent ?........thank you

rcorrigan5

I wouldn't mess with the vent hoses. They are put there for a reason. I don't fully comprehend the reason but you will most likely create a real mess if you start running a return line through one of those hoses. You'd be much better off using the appropriate sending unit (has connections for both the fuel feed line and the fuel return line).

Randy C.

InfoJunkie

What mods have you made that require fuel to be retuned to the tank?

compedgemarine

I may be wrong but I believe the two vents are in different locations inside the tank. using one as a return may cause more problems than its worth. as was stated you should really get the right sender with the return line built in.

knighthawk

you're probabley right, I'll take the sender out, try to look inside, just to see what's there., will maybe modify the sender, or replace it with the other style........ just thinking.....it is 40 years old .......... , maybe I should replace now anyway.... any one know what car model or part number will work ????

Indy_68_S

I'm curious about this too...

My '68 'S' (350 4bbl) has only a single line. I know that the BB cars got a return line (& maybe W-31s) & I've heard that the return line was to keep fuel circulating to keep it cooler in the engine compartment area.

Seems like the only parts needed would be the return line itself, the proper tank sender unit, & the proper fuel pump....and now is the time to do it since I'm rebuilding the chassis..

What say CO ? Any tangible benefit to a return line ??

rcorrigan5

It was my understanding as well that a single fuel feed line was used on all engines except the high performance engines, where a return line was also used. The single line sending units had just one lead, whereas the feed and return line sending units had two leads. In any case, if anyone is changing out their fuel lines and the body is off the frame, that is the time to do it. I changed mine out with the body on the frame and it was a royal pain. We actually had to loosen all the body bolts and lift the back end of the body a few inches above the frame to have enough room to install the new fuel lines. And we had to start our installation by running the fuel lines through the passenger rear wheel opening, between the frame and the body. It took a little manipulation of the lines, but the new fuel lines were bent in the beginning (to be boxed and shipped) so massaging them to fit in place wasn't that complicated. I've heard a number of people say that the fuel lines can be changed out with the body secured to the frame, but it's my belief (from actually doing it) that you would have to cut and patch new fuel lines if you were going to install them with the body secured to the frame.

The old GM part number for what I believe to be the dual lead gas tank sending unit (uses a return line) is 6428005. Its usage is for 400ci V8, except station wagons.

There are 2 other sending unit part numbers which I believe all to be for cars without fuel return lines. They are:

6427682 (6cyl & 350 V8 except station wagons)
6427768 (6cyl & 350 V8 station wagons)

There is another sending unit, p/n 6428004, which is used on station wagons but I am unsure of their application (possibly with the 400ci turnpike cruiser engine?).

Randy C.

jaunty75

Rockauto has fuel tank sending units specifically for this car. Cost is about $40, and you can get them with one or two lines.

http://www.rockauto.com

On my car ('67 Delta 88), the two-line units were used on cars with air conditioning while the single-line units were used on cars without it. When I replaced the sending unit on this car, which does not have A/C, I had to use a unit made for early '70s full-size Olds's as sending units are not made new for my year. All units for those years had two lines, and I just capped the unused one.

knighthawk

well, I know that a return fuel line allows a constant flow of gas thru the system , almost toatlly eliminateing "vapor lock'' due to heat build up the the engine compt as most fuel lines arn't to far from the exhaust stuff....thanks again guys