Using factory fuel lines for EFI
Thread Starter
Racer
Joined: May 2020
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Using factory fuel lines for EFI
I am looking at Holley’s Sniper EFI TBI set up and was wondering if I could use the factory inlet and return fuel lines with their in tank fuel pump on my ‘79? I would much rather use metal lines - instead of rubber lines most kits come with - without having to re-bend all new metal lines.
Race Director
Joined: Aug 2004
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From: Duvall, WA
You'll need to replace what little rubber line there is with Holley's VaporGuard line. The stock return fuel line is too small of a diameter, but you can get around this by using the fuel pump that doesn't require a return or by using Holley's filter/pressure regulator near the tank and doing a short return from that.
Filter/Pressure regulator
Filter/Pressure regulator
Last edited by rcread; Aug 19, 2020 at 05:48 PM.
Racer
Joined: Jan 2012
Posts: 321
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From: Ontario
I have FiTech EFI on both my Corvette and Camaro. The factory return line is too small.
On my C3 I replaced the factory fuel lines with 2x new pre-bent 3/8" stainless lines. I made connections at the tank and EFI with stainless braided PTFE lines.
On my Z28 I reused the factory supply line as a return line, making connections to the tank with stainless braided PTFE line. For supply I ran a new stainless braided PTFE line from tank to filter to efi.
Both have in tank fuel pumps.
On my C3 I replaced the factory fuel lines with 2x new pre-bent 3/8" stainless lines. I made connections at the tank and EFI with stainless braided PTFE lines.
On my Z28 I reused the factory supply line as a return line, making connections to the tank with stainless braided PTFE line. For supply I ran a new stainless braided PTFE line from tank to filter to efi.
Both have in tank fuel pumps.
Race Director
Joined: Aug 2004
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From: Duvall, WA
I'm using 3/8 supply and return for the Sniper EFI on my '72 LeMans with a Pontiac 400 and it works great. Holley recommends a 3/8 supply line and 5/16 return. Corvettes have a 1/4" return line.
Team Owner
Joined: Jan 2006
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From: Crossville TN
I can't imagine that the stock 'delivery' line would be too small (same fuel rate use, if you didn't change or drastically upgrade your engine); but you might have to replace (or install) the return line with larger than stock size. You can use Cunifer (nickel copper) line for that purpose. It is still all metal, but much easier to form. It is more expensive than plain steel, but well worth the over-cost due to the easy of forming and assembly.
Dr. Detroit
Joined: Mar 2012
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From: New Braunfels Texas
But if you run their in tank module......you need no return line at all.....it self regulates at the pump.....
Jebby
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Racer
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Not sure it's a good idea to use 40 year old lines that were never designed to have any real pressure run through them. Feed line to pump had virtually no pressure in them. Return line pressure was very low. These lines rust from the inside out. You're going to be running around 50 psi on the feed and around 10 on the return. Not worth the risk to me, especially after the money investment you have in the system and extras. Like 7t1 said, the copper nickle lines are the way to go. Very easy to form, virtually rust proof and designed for brake systems so should be good to 1500 psi.
Is my vette stock?? HAHA
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i will be using my stock lines and the Holley in tank module. It pumps out at 58psi and returns right into the tank like Jebby says. If 58 psi is an issue, then you should replace your lines. If you have a sealed tank and it gets hot the pressure will probably get higher that that. I see plastic tank inflate and pop the cork a lot
Last edited by Rescue Rogers; Aug 21, 2020 at 12:47 PM.
Racer
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From: Ontario
Burning Brakes
Joined: Feb 2016
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From: Round Hill Virginia
i will be using my stock lines and the Holley in tank module. It pumps out at 58psi and returns right into the tank like Jebby says. If 58 psi is an issue, then you should replace your lines. If you have a sealed tank and it gets hot the pressure will probably get higher that that. I see plastic tank inflate and pop the cork a lot
Is my vette stock?? HAHA
Joined: Oct 2015
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From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
I'll be installing mine starting next week and Ill do a thread. I'll be using the in tank sender with the pump attached. I'll use Earls rubber fuel line from my sender to the steel fuel lines as Holley instructs with fuel injection rated clamps. At the engine compartment end Im cutting the flare off the line and using Earls clamp on conversion to and AN-6 line. Then run it through my fuel cooler and a 10 micron secondary filter before it goes through the pressure gauge to the front of the EFI. Out the back I will run the return line from the stock regulator as a back up. If the in tank regulator fails I'll have the stock return line as an emergency return. I have a AN-6 to 1/4 inch liine so I can use the stock return and Ill eventually have a new fuel pressure gauge in the cabin so I can monitor the pressure....Guess I still have a paranoia over fuel pumps failing. As for the intake Im using the RPM inake thats on there with a 1 inch spacer which should take care of any issues with the divider and the MAP sensor. If it gets wonky I make take an inch out of the divider or switch to a TM-1 tarantula I just scored off of EBAY
Ill be running the Holley supplied relay and fuse. As well as a MSD distributor locked out and controlled by the MSD box and the EFI
Ill be running the Holley supplied relay and fuse. As well as a MSD distributor locked out and controlled by the MSD box and the EFI
Last edited by Rescue Rogers; Sep 3, 2020 at 05:46 PM.
Melting Slicks
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From: MA/NH Seacoast
I've run a few LS swapped cars with the stock steel lines. Just replace the rubber sections with fuel injection rated hose and good clamps. I even got fancy and installed flare nuts and flared out the ends of the stock steel line to hook them to AN braided hose, which went up to the rails.
I personally like using the Corvette style regulator mounted near the tank so I only need to run a feed up to the engine, and not a return.
I personally like using the Corvette style regulator mounted near the tank so I only need to run a feed up to the engine, and not a return.
Race Director
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From: Deep in the Pisgah National Forest
Use the stock steel lines in their current size but convert to EFI rated (high pressure) hose between. EFI pumps go to 100 psi then the pressure regulator bleeds off some fuel to the return line. It's not a lot of fuel going back so 1/4" should be fine. It is with my big block Ford project and I converted that five years ago.
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From: Deep in the Pisgah National Forest
Burning Brakes
Joined: Feb 2016
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From: Round Hill Virginia
I think theres a whole new sender unit that fits the stock Corvette tank that has the sender, pump, and regulator/return etc. Just plug the feed line into the steel line (assuming good steel line and proper hose and clamps) and connect the gauge/ground wires. I also hear running a relay in line with wiring is recommended - though I don't know what that does. 
Last edited by nix1981; Sep 3, 2020 at 08:31 PM.
Race Director
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From: South Western Ontario
LS3's can do 600+hp with a single 3/8" feed line and no return. Size the line to the engine power and it'll be fine.
Race Director
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