70-'72 fuel lines

[Goose]

Anyone replaced the vapor return fuel line in the 70-'72? This is the 5/16th in. line from the fuel pump to the tank? Can I do it without draining the tank first? There is fuel in the line since it is leaking from a hole in the line - just didn't know if that was residual fuel captured in the line or something else. Retailers offer a stainless replacement line as well as steel. Any significant advantage one way or the other? Thanks.

[dwaite72lnghrn]

That would be the fuel return line. Excess fuel from the pump returning to the tank. Some will bypass the fuel pump and will always be in the line when the truck is not running. You will have to plug the main line or fuel will leak all over. If the tank is full it will syphon out off the tank into the return line.

[badpeanut]

Not to hijack the post, but somebody told me only AC-equiped trucks got this return line. Is this true?

You could probably eliminate the line if you went to a 2-hole fuel pump without the return line provisions?

[Goose]

Good info guys. What is a "two hole" fuel pump. My truck did not have factory air ... looked to me like the return line was stock in 70-72 regardless of configuration. But if I don't need the return line it would certainly speed up the fix.

[dwaite72lnghrn]

Stock steel line is the cheapest (brake line) comes in different lengths. It lasted for 35 year the first time. If you eliminated it you would probably need a fuel regulator for the carb and it would really shorten the life of the fuel pump. If the tank is low, run a short rubber hose from the fuel supply side to the fuel return side as the pipes come off the fuel tank underneath. This would allow you all of the time you needed to change the return line and only loose the fuel in the pump and lines.
I would change both lines as if 1 leaked from rust the other is going soon.

[Goose]

Good suggestion on routing the fuel lines. I think a good tight hose clamp will make up for the od size difference between supply and return. Leak was caused by header rubbing the line and I didn't catch it quick enough ... or did I! Could have been lots worse. Thanks again.

[dwaite72lnghrn]

That rubber hose loop was to replace the lines without loosing the tank of fuel. DO NOT run crossed over between the lines, as fuel will still be running through the holely pipe.

[badpeanut]

Goose,

As I understand fuel pumps, there are three basic styles for SBC:
1) 2-hole short body
2) 3-hole short body
4) 3-hole tall body (taller in vertical direction making line to carb different shape)

2-holes = 1 line from fuel tank, and one line to carb
3-holes = 1 supply line from fuel tank, one return line to fuel tank, and one line to carb

My local parts store stocks all three. When I asked for a fuel pump for SBC they brought all three out and asked me which one I wanted.

[Goose]

Thanks badpeanut! I thought I knew what the hole arrangement meant, but I've learned not to assume too much. No dwaite72lnghrn, I won't attempt to run with crossover tube in place. The crossover tube is a great suggestion during this repair process though. I appreciate it.