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Ok so I'm in the process of figuring out my fuel system to install FAST EZ EFI on my 79. I'm planning to use the stock supply line and run a new 3/8" return line. The stock return line is only 1/4". My question involves the return line fitting at the tank. This fitting is only 1/4". Do I just get an adapter to run a 3/8" line to this fitting ? Or is that no good because the fitting will still be the bottle neck since it's the smallest point ? See pic below, the return line is the fitting on top.
If I DONT just use an adapter to run a 3/8" line to the 1/4" fitting, how do I go about installing a 3 /8" fitting on top of the tank ?
I have had DPFI on my SBC for some 20 years, and the pump is under the tank, tied to the chassis rail with a chunk of rad hose and a hose clamp, high pressure FI hose to the stock 3/8 OD steel line forward, and after the regulator on the engine, return is 5/16th OD to the top of the tank on pass side.....fuel pressure can go down to 33 psi, and that indicates plenty of flow to tank, I run engine at ~42 psi.....
Are you sure you HAVE TO have a 3/8" fuel return line for this fuel system?? Generally the fuel return is smaller than the supply line....that is why I am asking.
IF I HAD to do this. I would remove the sending unit and remove the pipes in it an sliver solder in new lines or fittings so I can attach my hoses to them. Possibly look at bulkhead fittings also and make sure that they can seal up well IF I used them and did not sliver solder the new hard lines back on.
I also would use a sending unit out of a 1982 so my fuel pump would be in the fuel tank and I also would fabricate up a reservoir on the sending unit to the fuel pump always had a source to draw fuel from so when making turns the fuel could not slosh around and possibly starve out the pump. And in doing this I would modify that sending unit so I could have good fitting on it to handle the higher fuel pressure and not use hose clamps
Not knowing exactly what you have or what you are doing if you are using an external fuel pump...then it is what it is. If you are using an external fuel pump just make sure your wire gauge is what the manufacturer specifies and do not use a smaller gauge wire. Bigger is better in that scenario.
As DUB has suggested, you need to change the inlet and outlets to 3/8.
Unless you do, you are restricting the input and output to 1/4 through the fittings even though your lines are 3/8.
My 69 return line is 5/16, not 1/4. If I were doing this I would hook up my new pump to just the existing lines and measure the pressures as you are currently set up. That is exactly what I did with my car, although it runs at lower pressures. Do the instructions with the system you are installing require this or just suggest it? A lot of work to change out that line otherwise.
As to the tank mods, tanks that have had gasoline in them scare me. DUB probably has experience modifying tank fittings and I would defer to most anybody on this subject.
I just finished installing an 82 sending unit, Walbro high pressure in tank pump, Holley hydramat, new Earls 3/8” Vaporguard pressure line, & 5/16” Earls Vaporguard returnline.
Just use a section of 3/8” rubber line from the steel line on the back fender to the 1/4” fitting on the sending unit (or whatever size it is) and use a good appropriate style clamp.
Adam
Last edited by NewbVetteGuy; Aug 26, 2018 at 06:01 PM.
Are you sure you HAVE TO have a 3/8" fuel return line for this fuel system?? Generally the fuel return is smaller than the supply line....that is why I am asking.
IF I HAD to do this. I would remove the sending unit and remove the pipes in it an sliver solder in new lines or fittings so I can attach my hoses to them. Possibly look at bulkhead fittings also and make sure that they can seal up well IF I used them and did not sliver solder the new hard lines back on.
I also would use a sending unit out of a 1982 so my fuel pump would be in the fuel tank and I also would fabricate up a reservoir on the sending unit to the fuel pump always had a source to draw fuel from so when making turns the fuel could not slosh around and possibly starve out the pump. And in doing this I would modify that sending unit so I could have good fitting on it to handle the higher fuel pressure and not use hose clamps
Not knowing exactly what you have or what you are doing if you are using an external fuel pump...then it is what it is. If you are using an external fuel pump just make sure your wire gauge is what the manufacturer specifies and do not use a smaller gauge wire. Bigger is better in that scenario.
DUB
Thanks for the info. Everything I've read reccomends a 5/16 or 3/8 return line. But this unit is supposedly also good up to about 650 hp depending on fuel pressure, so at my 400 ish level, I might be ok with only a 1/4" return.
I just finished installing an 82 sending unit, Walbro high pressure in tank pump, Holley hydramat, new Earls 3/8” Vaporguard pressure line, & 5/16” Earls Vaporguard returnline.
Just use a section of 3/8” rubber line from the steel line on the back fender to the 1/4” fitting on the sending unit (or whatever size it is) and use a good appropriate style clamp.
Adam
Ok so question on that, I'm using a Walboro external pump, so presumably the pressure from the tank to the external pump should be low (as in only a few PSI, so I don't need high pressure FI rated lines and clamps/connectors right?)
What about the pressure on the return side? Should I be using FI rated hose from the hardline to the tank, or is it all pretty low pressure in there?
Also one other dumb question, what kind of fitting is this ? Doesnt look like the normal -AN.
Part of that fitting isn't show in pic, there is also a collar that the hose goes into an then the part pictured screws into. If it says 3/8 return line modify to 3/8. My 6t8 has 1/2 pressure and a 5/8 return line. The 69 with a Holley sniper has both hi & lo lines in 3/8. As Dub suggested hose clamp connections at 60 psi isn't recommended. T
My 69 return line is 5/16, not 1/4. If I were doing this I would hook up my new pump to just the existing lines and measure the pressures as you are currently set up. That is exactly what I did with my car, although it runs at lower pressures. Do the instructions with the system you are installing require this or just suggest it? A lot of work to change out that line otherwise.
Since the 1/4" return line is already there, you don't have much to lose by trying this first. Put the pump in, loop the feed to return lines with a pressure gauge in the loop and fire the pump up. If you get less pressure then the FAST runs at then you actually can use the existing return line.
General rule of thumb is that the return line is no where near the pressure side. So even if you use a good FI rated hose due to it can handle higher pressure I would use it even though it is not under that high pressure.. In my head it is a safety factor.
I use that FI rated rubber hoses when I replace the hoses at the fuel tank for car like yours even if it was still a factory set up due to the cost of the hose is not that much more but it a better hose than a normal hose that I believe is rated at 50 psi.
Part of that fitting isn't show in pic, there is also a collar that the hose goes into an then the part pictured screws into. If it says 3/8 return line modify to 3/8. My 6t8 has 1/2 pressure and a 5/8 return line. The 69 with a Holley sniper has both hi & lo lines in 3/8. As Dub suggested hose clamp connections at 60 psi isn't recommended. T
gotcha, hadn't seen that before. I removed it and am just going to use the AN-6 Thread. I have a 3/8 braided SS hose that I will use for the connection from the 3/8 feed line to the throttle body. Still figuring out the return line, most likely will run a 5/16 hard line (assuming the stock return is 5/16 and not 1/4) from the throttle body to the original hardline.
Since the 1/4" return line is already there, you don't have much to lose by trying this first. Put the pump in, loop the feed to return lines with a pressure gauge in the loop and fire the pump up. If you get less pressure then the FAST runs at then you actually can use the existing return line.
True. The FAST system has a regulator on the return side, presumably it wouldnt be able to maintain 43 PSI (the recommended setting from FAST) If the return line was too small?
General rule of thumb is that the return line is no where near the pressure side. So even if you use a good FI rated hose due to it can handle higher pressure I would use it even though it is not under that high pressure.. In my head it is a safety factor.
I use that FI rated rubber hoses when I replace the hoses at the fuel tank for car like yours even if it was still a factory set up due to the cost of the hose is not that much more but it a better hose than a normal hose that I believe is rated at 50 psi.
I had this system... and I upgraded it to the FAST XFI with throttle body... I would suggest you do the same... a few hundred dollars more, but a LOT more flexibility in the tuning, and maps/data out for troubleshooting... you do not have this with the EZ.
Also, YES, the return line will NOT work properly with the 1/4" line, needs to be changed
Last edited by pauldana; Aug 27, 2018 at 03:29 PM.
Upgrading return line to 3/8"
