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I inherited a clusterfuck of a 78 Vette from my father who passed. I’m going to finish the car for him but give it some new tech. I had a 5.3 laying around and put a dorman LS6 intake and a LS9 cam I had laying around. I originally wanted to run a supercharger I had laying around but it ended up not fitting. So I’m putting together the fuel system and it came with 3/8” feed line and a 1/4” return line from the mechanical pump on the 383. I dropped the tank and swapping the sending unit for a 82 unit which had a in tank fuel pump. I have a aeromotive 340 laying around but figured that’s way to much pump for this 400-420hp setup and the small return. I am using a aeromotive external regulator that I had already and billet rails with 60lb dekas (overkill I know but I don’t have anything smaller). I could get a walbro 255lph and hope it flows less to not overpower the 1/4”
return. But I wanted to ask you guys before obviously commuting. FYI running new fuel lines on a C3 is a PITA and im not pulling the body off the frame. As you can also tell I’m. It trying to sink a lot into the car as the car needs ALOT of work. Remember the 82 sender I believe also has a 1/4” return at the sender so I don’t see how upgrading the return is worth it since it will still have a bottle
neck.
so 1/4” return with a 340 or 255... will it be too small?
future plans of forced induction prob in the form of a turbo or two Inless I can find another SC bracket that clears the hood and Aarm on this Vette.
I'm running twin 255's with a 3/8" feed and 5/16" return. I was able to turn both pumps on with the engine off and dial the fuel pressure down to 42psi. Are you running a rail mounted regulator?
I think you'll be ok...you can always give it a shot on a 255. worse case scenerio...you just run a new line.
The Higher base pressure of 58 psi will also help.
1/4" is small, it may be doable with a 255, but ideally you'd want larger.
And a higher flowing pump will only be worse.
Other option is to PWM the pump based on load, so the return itself will always be seeing less fuel anyway.
Thats what I figured I doubt for a long time I will want more than 400-420hp on this setup since the rear end and half shafts won't handle more than that or the 400hp if I hook for whatever reason. Neither of those options look cheap lol and pulling the body off to replace fuel lines is not fun on these cars since the lines are under the body and on top of the frame for the rear 50% of the car.
While I hate the corvette filter/regulator combo it might be a good idea on this car. I figure a 255lph and just run the stock line up to the motor. I hate only having 1 feed to the engine tho and I technically have the regulator already however the aeromotive regulators don't hold pressure for **** like OEM as I have the same regulator on my 87 trans am with a 5.3 turbo which is my "fast car". Only think besides the single line to the front engine is that I can't run 43psi to keep my injectors at 60lb, @ 58psi they will become 70-72lb which is wayyy overkill for a cammed NA 5.3.
For the PWM I think the holley term x does that right? I'm not sure what I'm doing for the EFI, I was going to run my stock PCM which runs a 2bar OS on HP tuners bc its free lol. But I could go Fitech or Term X but I need to power the stock tach so I think only the Term X has that ability.
Thats what I figured I doubt for a long time I will want more than 400-420hp on this setup since the rear end and half shafts won't handle more than that or the 400hp if I hook for whatever reason. Neither of those options look cheap lol and pulling the body off to replace fuel lines is not fun on these cars since the lines are under the body and on top of the frame for the rear 50% of the car.
While I hate the corvette filter/regulator combo it might be a good idea on this car. I figure a 255lph and just run the stock line up to the motor. I hate only having 1 feed to the engine tho and I technically have the regulator already however the aeromotive regulators don't hold pressure for **** like OEM as I have the same regulator on my 87 trans am with a 5.3 turbo which is my "fast car". Only think besides the single line to the front engine is that I can't run 43psi to keep my injectors at 60lb, @ 58psi they will become 70-72lb which is wayyy overkill for a cammed NA 5.3.
For the PWM I think the holley term x does that right? I'm not sure what I'm doing for the EFI, I was going to run my stock PCM which runs a 2bar OS on HP tuners bc its free lol. But I could go Fitech or Term X but I need to power the stock tach so I think only the Term X has that ability.
Keep in mind you can run Nylon OEM style line for a return if the 1/4" was really an issue. I ran lengths of 3/8" nylon fuel line with quick connect fittings.
I'm running twin 255's with a 3/8" feed and 5/16" return. I was able to turn both pumps on with the engine off and dial the fuel pressure down to 42psi. Are you running a rail mounted regulator?
I think you'll be ok...you can always give it a shot on a 255. worse case scenerio...you just run a new line.
The Higher base pressure of 58 psi will also help.
interesting.... My regulator will be external. I have the crossover set at the rear of the intake and regulator mounted to the front pass head. Not enough room on the front driver side or the rear pass side so that left me at the rear driver or front passenger but off the rail as all the throttle linkage is in the way. See pics, plus the OEM pressure and return line are right there on the frame rail so I was hoping to run short lines to the rails.
Keep in mind you can run Nylon OEM style line for a return if the 1/4" was really an issue. I ran lengths of 3/8" nylon fuel line with quick connect fittings.
I always liked the price point of the nylon lines but never understood the fittings and all that crap. Gotta be a way to make an AN attachment to nylon fuel lines. I was going to pick up some 3/8" nicop hard line and AN tube nuts to bend some tight lines under the intake for the driver side hookup of the fuel rail as I would run the line under the TB area. But If I ran the corvette filter assemble I wouldn't have to worry about that and could easily hook right into or run a new single feed.
I internet confirmed the new sending unit comes with a 3/8" feed and 5/16" return line on the sending unit. Those connections are hose barb for the TBI fuel pressures. I was going to run sythetic rubber 250psi rubber hose to AN at the steel line but they don't make 5/16" tube nuts and slipping 3/8" hose over 5/16 barb usually doesnt work so well.
How would you guys adapt 5/16" hard line? You can't use -6 tube nuts right? I'm just trying to figure out if I had to upgrade the return it would have to be 3/8" or -6an PTFE style line.
Also I'm having a hard time locating the correct walbro 255 pump with the 11mm inlet (sock side) that way if I wanted to spend $150 on the hydramat I could get one that fits.
How would you guys adapt 5/16" hard line? You can't use -6 tube nuts right? I'm just trying to figure out if I had to upgrade the return it would have to be 3/8" or -6an PTFE style line.
Also I'm having a hard time locating the correct walbro 255 pump with the 11mm inlet (sock side) that way if I wanted to spend $150 on the hydramat I could get one that fits.
Summit number- Earl's AT165156ERL
I used these to adapt AN line to my stock sending unit, 80's GM too!
I used the stock lines and mounted the corvette regulator under the pass side frame rail. Then ran -6 an to the returnless rail. Its really easy and the car doesn't have issues but the body is off the frame.
Can also use dual fuel pumps if PWM isn't an option. Run a 165 walbro or even a stock fuel pump. Then have a 255 or similar inline pump kick on under boost. Or with a WOT switch. Pressure is a good thing for low buck setups. I run 70 base without the vac line. 80lb injectors and 19lbs on a small cam 5.3. Its barely enough fuel to squeak by on e70ish. (I run the flex fuel sensor). Also FWIW I run a surge tank filled by the OEM pump and tank. I run the regulator at the surge tank in the trunk and a single 1/2 line to the front of factory rails. It works well.
Bit of a cluster fark now that I went to a dual pump surge tank. But the previous single pump setup was pretty clean. Everything is mounted to it. Pressure sensor, filter, e85 sensor, temp, regulator etc... single AEM 380 got me 560whp and 600 ft lb on e60ish @ 12lbs. I feel like dead headed systems give up quite a bit in the flow department. My pumps never go as far as a proper return system it seems.
Last edited by Forcefed86; Sep 30, 2020 at 03:21 PM.
I used the stock lines and mounted the corvette regulator under the pass side frame rail. Then ran -6 an to the returnless rail. Its really easy and the car doesn't have issues but the body is off the frame.
That's what I was thinking of doing. I just don't like the idea of the corvette filter and the higher pressure. I guess it doesn't matter however all I have are 60lb Deka's at LS1 height and that's at 43psi. I wanted to mount the regulator to the frame as well but thought the mufflers tuck up there and it would have to be on the side of the frame? Would be easy to run a single 6an braided line up to the front of the car. My rails are billet but can be setup as returnless via a plug on one end.
Can also use dual fuel pumps if PWM isn't an option. Run a 165 walbro or even a stock fuel pump. Then have a 255 or similar inline pump kick on under boost. Or with a WOT switch. Pressure is a good thing for low buck setups. I run 70 base without the vac line. 80lb injectors and 19lbs on a small cam 5.3. Its barely enough fuel to squeak by on e70ish. (I run the flex fuel sensor). Also FWIW I run a surge tank filled by the OEM pump and tank. I run the regulator at the surge tank in the trunk and a single 1/2 line to the front of factory rails. It works well.
Bit of a cluster fark now that I went to a dual pump surge tank. But the previous single pump setup was pretty clean. Everything is mounted to it. Pressure sensor, filter, e85 sensor, temp, regulator etc... single AEM 380 got me 560whp and 600 ft lb on e60ish @ 12lbs. I feel like dead headed systems give up quite a bit in the flow department. My pumps never go as far as a proper return system it seems.
I like Swirl tanks/front fuel stations if you have basic fuel pump in the tank but need high HP fueling. Since this is considered low HP to me It would be overkill to setup something like that. A single 255lph will be more pump than this car will ever need.
So today I ordered the Walbro F20000169 255lph High Pressure Fuel Pump & Installation Kit which I got for $80 shipped. It has a larger 19mm OD inlet so I can't run a 11mm hydramat I guess. I'm gona rock it and see how it does. Got the new sending unit today and verified full SS (very nice) and has 3/8" feed and 5/16" return. Vent looks like 5/16" necked down to 1/4". If I ran the Corvette filter I would get a WIX filter and buy the fittings separate as it looks like everyone has kits but I read alot about failures even summit, tanks inc, ebays etc.If I convert the 5/16" to 3/8" barb I could run -6an for both to the regulator and then single -6an to engine.
Can also use dual fuel pumps if PWM isn't an option. Run a 165 walbro or even a stock fuel pump. Then have a 255 or similar inline pump kick on under boost. Or with a WOT switch. Pressure is a good thing for low buck setups. I run 70 base without the vac line. 80lb injectors and 19lbs on a small cam 5.3. Its barely enough fuel to squeak by on e70ish. (I run the flex fuel sensor). Also FWIW I run a surge tank filled by the OEM pump and tank. I run the regulator at the surge tank in the trunk and a single 1/2 line to the front of factory rails. It works well.
Bit of a cluster fark now that I went to a dual pump surge tank. But the previous single pump setup was pretty clean. Everything is mounted to it. Pressure sensor, filter, e85 sensor, temp, regulator etc... single AEM 380 got me 560whp and 600 ft lb on e60ish @ 12lbs. I feel like dead headed systems give up quite a bit in the flow department. My pumps never go as far as a proper return system it seems.
A dead head done right, should require less in terms of flow, because you do not need to accommodate the losses required by the FPR and them needing some degree of return.
Most efficient in terms of pump flow usage is a dead head with no FPR, and pump speed controlled to regulate pressure instead of a FPR.
Zero loss in that system.
I think Vaporworx offered something like that ? Or some modern OEM's do similar, but it's not overly common
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1/4” return with a 255 or 340 pump? 
