72 Project

I plan on using fuel injection. Do they require a return line? How large does the fuel line need to be? How large does the return line need to be if needed? I WILL be running about 600 rear wheel bourse power if everything works out.

Thanks

Jim

Tiger Joe

Yes fuel injection needs a return.


Just bought a Holley sniper setup haven't installed yet but I believe it uses 3/8" for both the feed and return.

jim2527

Some people use the existing carb supply line and convert it to a efi return line. That way all you need to is an efi supply line.

mrvette

My car runs 40-42 lbs, 355 engine, DPFI, 3/8 supply from pump in back, return line to top of tank is stock 5/16? diameter.....

runs well.....'72 vette

hugie82

Edelbrock now makes an adapter for your fuel system. It's feed by your regular fuel pump into a small tank and then there is a high pressure pump in that tank that ramps it up to 45-50psi. The excess fuel going through the bypass circulates back to the small tank. The hardest part is finding a spot for the gallon and half tank. Or you can get an 82 tank with the return built in for FI

GUSTO14

Edelbrock Universal Sump Fuel Kits 3605

https://www.summitracing.com/parts/e...FdKEswod9AkJGA
The Edelbrock EFI kit provides you with a Sump Style Fuel Kit. The Sump Style Kit is designed to provide the engine with the necessary high fuel pressure required for an EFI conversion. The complete self-contained bottle system can be installed under the hood of your classic Ford. Edelbrock designed this system to deliver a constant fuel pressure of 49 psi or 60 psi, which is ideal to properly run an EFI System. This will not require a fuel return line.

GUSTO

lionelhutz

The Edelbrock kit saying no return line is somewhat deceiving. There is a vent line that must go somewhere. The instructions say to route the vent to the charcoal canister, fuel tank vent or back to the fuel tank.

A solution for the fuel system without changing the tank has been around for a long time.

Get a small $50 tank off Ebay and an external electric pump suitable for your engine and EFI system.

Cap the return line on the mechanical fuel pump or change the mechanical fuel pump to one without the return line fitting. Put the output of the mechanical pump to the new tank and take a fitting off the top of the new tank back to the existing return line.

Use 2 other fittings off the bottom of the new tank to feed the electric pump and for the EFI return.

The mechanical pump will keep the new tank full so the electric pump always has fuel available to feed the engine. The return line back to the main tank coming off the top of the new tank means that any air will be pushed back to the main tank.

It's not as convenient as the Edelbrock system since you have to figure out the details yourself, but then it won't cost you $600 either.

SteveG75

Return vs returnless...that discussion is almost as old as Chevy vs Ford.

Bottom line, return is not required if the system is designed right. LS motors have used returnless for years.

I originally used a return system on my 496 BBC with FAST XFI and was having issues with the returned fuel getting hot and vaporlocking the pump. I now run a 1/2" feed returnless system with no issues. My pump is in the tank and regulator is right below the tank. Short return from regulator to tank. Regulator set at 42 psi and not vacuum referenced. No issues in two years with this setup.

lionelhutz

So, your return line is just short....

SteveG75

Yup, basically LS style. This way I am avoiding heated fuel back into the tank which was causing vapor lock.

gdh

I would be more apt to use a C5 regulator like Steve does but if you really want a surge tank, lionelhutz's method will be an excellent inexpensive route or look into a RobbMc Powersurge sump (@$280).

72 Project

Do I need a 1/2 inch feed line? Did any C2 or C3 come with a 1/2 inch feed line? What size are the feed and return lines on a 72 BB?

gdh

Your original 3/8" will be fine. What efi system are you looking at? I believe that the bb rtn (vapour) is 5/16" same as the sb. Just looked in the AIM and it doesn't state anything different btn the sb and bb.

lionelhutz

You think the pump was actually sucking vapor? Getting the fuel in the tank to around 200*F is quite a feat.

You certainly won't vapor lock the high pressure side of an EFI fuel system. The fuel would have to be something like 350*F to vaporize at 42psi.

USAFVeteran

My LS-5 build is about 550hp, running a FAST fuel injection system. I ran a new 3/8 feed line (Teflon lined braided) from the new in-tank pump I installed to the throttle body, and I used the original supply line (not the old return, it's too small) for the return. I have had no fuel supply or return issues.


Good luck

72 Project

I'm thinking of using 2 of the stock feed lines, together in the stock location with an in tank pump. For EFI unit either the Sniper or the Fitech 600 hp. Would the 2 stock feed line idea work?

USAFVeteran

Depends on the size. A 3/8 line would work for either feed or return. But a 5/16 I don't think is a good idea. But, it's your car. I want all the fuel to and from I can get, to not have a chance to create a problem

Zip Corvettes

Don't make it more difficult then it needs to be. Just run -6AN fuel line for feed and return. You have to have a return coming from the regulator, this is how it keeps the correct fuel rail pressure. It is too easy this way to try and re design it into a C5 setup which still has a return, it is just very short. If you think you will be more the 600HP then you may want to make your feed line a -8AN, but you will need some serious pump to be able to flow this amount a fuel at 4 bar if that is what your Holley system is requiring.

USAFVeteran

That's what I said....didn't I?

SteveG75

FYI, I am running an Aeromotive Phantom 340 in tank pump to an Aeromotive Regulator and Filter. From there, it is -8AN all the way up to the fuel rails and there is a -8 line connecting the rails at the front. I also run an Aeromotive fuel pump controller.

This is heading a 496 BBC making 413 rwhp. Tuner says I am choked by my sidepipes and could easily make more.

I am using the Goodridge 810/911 (or it might be 811/910) line from Pegasus Racing. Easy to use fittings and flexible PTFE liner makes running lines a breeze.