Add return line to tank

[MNorby]

My 71 didn't come with a gas tank. A guy gave me a tank but it doesn't have a return. Has anyone added a return to one of these or have any other tips?

[snj8198]

When I converted to EFI I drilled a hole through the sending unit parallel to the supply line and welded a chunk of 3/8 hard line in place. Becareful of using too much heat here and beware of possible sender failure. I bent the line parallel and welded a brace strap to the pickup, and at the bottom I bent it to discharge away from the sock. You could also install an AN bulk head fitting instead of hard line if your going for looks and don't mind spending a little money. -steve

[MNorby]

sweet, that was my best idea I came up with too. I will get some metal line and put a 90 in the top and weld it in there.

[VinceY]

Originally Posted by snj8198

When I converted to EFI I drilled a hole through the sending unit parallel to the supply line and welded a chunk of 3/8 hard line in place. Becareful of using too much heat here and beware of possible sender failure. I bent the line parallel and welded a brace strap to the pickup, and at the bottom I bent it to discharge away from the sock. You could also install an AN bulk head fitting instead of hard line if your going for looks and don't mind spending a little money. -steve

I did the same thing. Soldered not welded.

[BobbyK]

I made a "T" and ran my return into the fuel fill tube.

Been working fine since my TPI swap back in 2000.

[MNorby]

I thought about returning back to the section line before my fuel pump (elec pump on frame as close to tank as possible) but was worried about warm fuel going back to engine and running out of fuel it would cavitate pump instead of priming. Going to fuel filler or vent would work though

[snj8198]

Dumping the return fuel via the fill tube will work if you have a sump or baffleing in the tank, your pick up is on the opposite side of the tank, or you are running a carb. However!! When I first converted to EFI I plumbed my return into the filler neck for ease. My tank does not have a sump or baffleing so when the return fuel splashed into the tank it airated the fuel creating lean spots which hiccupped the motor enough to wipe out a cam lobe on my fresh 496. I could tell I was running extremely lean but didn't know why. I swapped in a new cam, fattened up the mixture with the EFI controller and triied again but wipped out that cam too. After a good cuss session I found my problem.
If I had a sump or baffleing the fuel within that area would have been protected from airation. If the pickup tube was directed to the other side of the tank it would have been far enough from the puddling fuel. If I was running a carb, the fuel in the floats may have sufficiently fed the motor, however I believe this to be true only if the tank remains atleast 1/4 full and minimal fuel sloshing which we all know is not practicle.
Moral of the story, do it right the first time! -steve

[Jason915]

Originally Posted by snj8198

Dumping the return fuel via the fill tube will work if you have a sump or baffleing in the tank, your pick up is on the opposite side of the tank, or you are running a carb. However!! When I first converted to EFI I plumbed my return into the filler neck for ease. My tank does not have a sump or baffleing so when the return fuel splashed into the tank it airated the fuel creating lean spots which hiccupped the motor enough to wipe out a cam lobe on my fresh 496. I could tell I was running extremely lean but didn't know why. I swapped in a new cam, fattened up the mixture with the EFI controller and triied again but wipped out that cam too. After a good cuss session I found my problem.
If I had a sump or baffleing the fuel within that area would have been protected from airation. If the pickup tube was directed to the other side of the tank it would have been far enough from the puddling fuel. If I was running a carb, the fuel in the floats may have sufficiently fed the motor, however I believe this to be true only if the tank remains atleast 1/4 full and minimal fuel sloshing which we all know is not practicle.
Moral of the story, do it right the first time! -steve

Interesting, I did the same thing on my TBI conversion and it's been working just fine. I did take some tubing and routed it as far into the tank as I could before I connected it to the tee on the outer side of the filler though.

[snj8198]

Two reasons we experienced different findings Jason:
1) i did not run a tube down into the tank to ease the fuel back in (stupid mistake), now it's plumbed through the sending unit to the bottom.
2) MPI is a high pressure system, TBI is low pressure. I'm speculating the that nature of TBI may be more forgiving than MPI however I am unsure the technical reason why.
Regardless it was hard lesson learned but finally walked away with quite a bit of info and a great running motor in the end. Good Luck! -steve