Gator81

This question is directed to those among you who've converted your C3 to fuel injection, although the '81 and '82 owners may know about this, too.

My '81, with its stock fuel system, has two lines between the tank and the fuel pump. The larger of the two is the supply line. I can only assume the other one is a return line. I don't understand why a carbureted car with a mechanical pump running, like, 6 psi of fuel pressure needs a return line. 'Splain, please? :confused:

And here's the real question: If I were to ever get a serious wild hair about converting to EFI (I've always wanted to put a TPI on my crate motor!) would that second line be adequate as a fuel return line for the EFI system? Being able to keep my mods in the engine compartment would be a significant simplification to the conversion, it seems to me...

TIA! :flag

Fevre

The stock return line is too small but the vapor cannister return line is large enough, it is on the drivers side in my 73, not sure if got one in your 81.

TJKirby82CE

1981 I thought that year was a computer controled fuel injected car.

Smokehouse69

Many 'vettes had a return line as far back as 1968, that I know of. Some of the mechanical pumps had a return line built in to them and some cars (my 69) had a small return line exit the filter. I assume that this was part of the pressure control on the pump itself.
I've been led to believe that the line itself is too small to work as a return line for a TPI conversion.
Some 'vettes actually have another line returning to the tank that is large enough, it is exit the charcoal canister. I think Zwede used this line for his return when he converted to TPI last year. I considered a TPI conversion in the past, I planned on using the old feed line for the return and add a new line for the main fuel line.
Some people have used stainless steel braided armored hose for fuel line, it is easy to use and fairly secure, at least much better than rubber fuel line. The other alternative is to replace with steel tubing, it can be done with the car still on the frame but it will take some creative manuvering to do it.

mrvette

I have found the 1/4 inch carb return line to be just fine for the return to the tank....no pressure/delivery problems from using the stock steel lines that were on my '72....now I use Erols hose double clamped on the steel lines..and adaptor fittings on the TPI setup....

GENE

PatsLs1vette

I changed mine to 5/16 since i already was changing to new lines.

lone73

Or you could run new 1/2" braided line beside the stock supply line as a new F/I supply line and return using the stock fuel supply tube. That's what I did on my '73 and it works fine. That also leaves your vent line and cannister intack and functional.
good luck
dr

Fevre

Got any post of your set up? Sounds very interesting.

Tom73

'81 was a computer controled carb. The FI came in 82.

tom...

shawn_cake

Don't use a small line for the EFI return. Use the same size line as the feed from the fuel pump. Use of a small return line will cause problems at low RPM / low engine load conditions..

I found out the hard way!

:crazy: :banghead: :crazy:

AndyAA

My opinion is that the return line was desgned to circulate fuel to keep it cool and avoid the dreaded vaper lock problem.

Andy Anderson