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Greetings!

My 1970 el Camino has a single fuel line from the tank to the fuel pump. I'd like to add a return. Do I want to get a new primary line and use the existing as the return, or do I just need to add a return line?

Second question, where would the return line feed back into my tank?

Thanks in advance.
 

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Re: Return fuel line on 1970 el Caino

Why do you need a return fuel line? Are you changing the engine to a fuel injection system such as what a Chevy LS engine uses that needs a return?

Rick

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Discussion Starter · #3 · (Edited)
Re: Return fuel line on 1970 el Caino

Why do you need a return fuel line? Are you changing the engine to a fuel injection system such as what a Chevy LS engine uses that needs a return?

Rick

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How does this help answer the question?

[Edit] That sounds a bit snarky, doesn't it? What I mean is does the type of conversion make a difference to the type of return? I didn't even know there were options. Does an LS conversion (not that I'm doing one) have a different return than, say, an aftermarket EFI?[/Edit]
 

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I can't directly speak for an aftermarket EFI but a stock carbureted engine usually does NOT need a fuel return line back to the tank. Carbureted setups run a quite low pressure fuel pump (maybe 5-6 PSI) so there's no need for a return. An LS engine definitely needs a fuel return because its fuel injection system operates at 55-60 PSI at the fuel rail. LS engines have return line plumbing at the in tank fuel pump access port on top of the tank - usually two 90 degree bends in the tubing - one going out and the return going in. The return also helps keep the fuel cooler to prevent vapor lock depending on how close your fuel lines run to a hot exhaust pipe.

I'm also learning a lot about this while reading two books on LS engine swaps. One book was written in 2011 and the other is fresh up to date in 2017 with all the latest aftermarket stuff but I have many learned things . . . a lot of expensive things to buy . . . from both books. My 5.3 LS / LM7 Chevy truck engine sits in the corner of the shop waiting to go in someday. However, I have to get through sheet metal repairs first before I can start spending money on an engine installation. But 1300 bucks for a good running LM7 engine with good, 170 PSI compression and the heads rebuilt 3000 miles ago and its 4L60E transmission still mounted was too nice of a deal to pass up. The truck ran well and moved under its own power throwing no codes until it got yanked out three weeks or so ago - truck was totalled for sheet metal damage. I also got the powertrain control module, the wiring harness, the MAF and all intake plumbing, etc. Deal of The Century from a shop that I trust.

Rick
 
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Discussion Starter · #5 ·
But 1300 bucks for a good running LM7 engine with good, 170 PSI compression and the heads rebuilt 3000 miles ago and its 4L60E transmission still mounted was too nice of a deal to pass up.
Rick
If I found a deal like that I'd have one sitting in my garage waiting...

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1970 El Camino SS396, VortecPro 467, ATI TH400, Moser 12 bolt /TruTrac 3:42, Hedman headers
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FWIW..My 70 El Camino SS has a 3/8 inch line to the fuel pump but it also has a smaller "return line" running along side of it, I believe the smaller line may have been connected to the fuel pump originally.
 

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Just some 70 Trivia:
If you have a fuel pump on your 70 with a 3/8" line and a 1/4" line.
First... ALL 1970 Chevelles have a Closed engine vapor system. What the hell is that?
ALL engine fumes, Crankcase, Valve covers, fuel system. All and ANY fuel or engine vapors are ENTERED into the engine and burned off and out the tail pipe.
Example: 454 engine, Left side valve cover is vented into the intake. R.S. valve cover is vented into the Air Cleaner. That Quarter inch Return line at the fuel pump. What is does is allow the gasoline tank fumes & vapors to travel to the fuel pump, Then the vapors are pumped along with fuel to the Carb. It is all burned off,,,,, Then-- EXITS Via. the tailpipe.
I call it a vapor line.
Bob
 

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Your making the right move with todays fuel..

Use 1/4" steel brake line tubing for your return. The new tubing is nice to work with..

Pick up a new sending unit with the return port or drill and solder a nipple into the existing.

Put a 3/8" x 3/8" x 1/4" tee on the supply side of the fuel pump.. Or use a fuel filter for a 1964 Pontiac Bonneville with AC.... The closer you can get the return pick up point to the carb the better..
 

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Saw a video of a guy that did it to stop vapor lock problems, and it does seem like a good idea as you will end up with cooler fuel to the carb, I was curious and asked around but just got post's about carbs not needing it, but I say go for it, when I re do my fuel tank I'm going to add a return line to the sending unit or maybe use one of the EFI conversion tanks from tanksinc.com
https://youtu.be/YUmaAQoHggM
 

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FWIW..My 70 El Camino SS has a 3/8 inch line to the fuel pump but it also has a smaller "return line" running along side of it, I believe the smaller line may have been connected to the fuel pump originally.
Saw a guy that tried to use the smaller line for EFI fuel return, it seems there is some sort of restriction somewhere in the line so it only works for vapor as Robin mentioned.
 

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Bill
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Just some 70 Trivia:
If you have a fuel pump on your 70 with a 3/8" line and a 1/4" line.
First... ALL 1970 Chevelles have a Closed engine vapor system. What the hell is that?
ALL engine fumes, Crankcase, Valve covers, fuel system. All and ANY fuel or engine vapors are ENTERED into the engine and burned off and out the tail pipe.
Example: 454 engine, Left side valve cover is vented into the intake. R.S. valve cover is vented into the Air Cleaner. That Quarter inch Return line at the fuel pump. What is does is allow the gasoline tank fumes & vapors to travel to the fuel pump, Then the vapors are pumped along with fuel to the Carb. It is all burned off,,,,, Then-- EXITS Via. the tailpipe.
I call it a vapor line.
Bob
Wrong. There is a 1/4" return line on a three port fuel pump or a 3 port fuel filter depending on the year. It returns a small amount of fuel back to the tank to help prevent vapor lock. This keeps fuel from sitting in the line between the pump and the carb and getting hot. It does not vent the tank. A tank vapor line goes from the tank to a charcoal canister, if equipped.
 

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Bill
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Greetings!

My 1970 el Camino has a single fuel line from the tank to the fuel pump. I'd like to add a return. Do I want to get a new primary line and use the existing as the return, or do I just need to add a return line?

Second question, where would the return line feed back into my tank?

Thanks in advance.
Feed line should be 3/8", return line is 1/4" in a factory carb set up. HP fuel systems use a larger return line in a bypass regulator setup. The factory return setup has a tiny hole restriction so anything bigger than 1/4" would just be a waste.
 

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Wrong. There is a 1/4" return line on a three port fuel pump or a 3 port fuel filter depending on the year. It returns a small amount of fuel back to the tank to help prevent vapor lock. This keeps fuel from sitting in the line between the pump and the carb and getting hot. It does not vent the tank. A tank vapor line goes from the tank to a charcoal canister, if equipped.
So, it could be used as a return line for a mechanical fuel pump? I thought this was the case too but others have talked me out of it. I know it didn't work for one guy but he was using a high pressure electric pump. Does the line return to the tank or the vent box? Thanks.
 

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Bill
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So, it could be used as a return line for a mechanical fuel pump? I thought this was the case too but others have talked me out of it. I know it didn't work for one guy but he was using a high pressure electric pump. Does the line return to the tank or the vent box? Thanks.
Some cars came with this 1/4" return line that goes back to the tank, yes for a mechanical pump. They make a tank sending unit with this 1/4" return line connection. I was fighting vapor lock problems and added this return line to mine. I won't say that it fixed my problem, but it was one of the many things I did and they all seemed to make it better.
 

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Not sure about other 1970 SS 454s-with a 4 speed. The 454 I have has the three port fuel pump. My 454 has no charcoal canister.
I have a question? If you do not have a charcoal canister attached to your 1970- SS 454, What happens to the fuel VAPORS ?
We all know they "do not" exit to the Atmosphere, My question is, Where do the fuel vapors in the fuel tank " GO " on a 1970- LS-5 ?
The answer is ........................................................................ ?

Bob
Trivia:
The 1/4" port on the three port pump. To make my 1970 Sta.Wgn. ( Driver ) 454 Engine look like a Real factory LS-5 with the LS-5 -3 port pump.
I attached a piece of rubber hose to the fuel pump and then shoved a piece of old brake line into the other end of the rubber hose installed the correct spring clamps, Then I shoved it back into the frame rail. NOW my fuel system " LOOKS " like a factory LS-5. :thumbsup:
My FRAUD car ( with papers to prove it) SS 454 Sta. Wgn. has been driven over 38.000 miles, And so far I have not seen any fuel come out of the small line ( That is laying on the frame, and goes nowhere. beside the org. 5/16" -307 fuel line,) On my 3 port long canister fuel pump.
Also , For a driver / Cruiser, my 468 runs and operates just fine on the org. 307-5/16" fuel line.
 

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Some more trivia from an old guy:
What does the so called term vapor lock mean? Think about this: When you boil water it turns to steam or VAPOR, When you boil Brake Fluid it turns to VAPOR. In 1962 drag racing my C/G 38 Chevy. At the end of the 1/4 I had NO BRAKES. Kill the engine and in a few seconds I had a full pedal.
Cause: Headman Headers blowing hot exhaust on brake line.
When you boil gasoline it turns to VAPOR. A 7040205 will no operate on VAPOR, Must have liquid.
So I Call my Brother in law Bill, From Mich, He says call my friend BOB, I call Bob and answer many questions for this Bob guy. He tells me on the phone the problem with my 70 454. So I do what this Bob guy tells me to do.
After I follow Bobs instructions, I now have no more Vapor Loc.
FACT: My one owner LS-5 never got hot or had vapor loc. So what changed.
I had a BAD Eaton Fan clutch.
Fact #2: 1970 " A " body Chevelles all models had an Airflow Ducted engine bay. What the hell is that? I means, All the air that enters the engine bay is FORCED to EXIT ( By road speed or by the engine powered exhaust fan.)
Fact#3: A 1970 engine bay is designed to have the Super Heated Air Exit at the rear of the Lower right & Lower left cast Iron manifolds.
Fact #4: Changing any factory under-hood installed items (rubber seals and such) , So when you re/engineer your engine bay cooling system, And you also think a lot of what this guy just is a big load of Bull Sh!T.
All this stuff about duct work and sealed off engine bay stuff and moving " X " number of cubic feet of air per min. sounds fishy.
When your home A/C or your furnace is running. Use caution !
Remove the blower belt, ( You better have " Super Heat switches working " And then lets talk about Air Flow and Duct work.
Just some trivia, From an old Guy. :thumbsup:
Bob
P.S. So you know, My B.I. law Bill was a boss at FORD the Wayne Assmb. plant for 37 years. The Bob guy I speak of was a Thermal Engineer for Chevrolet for 39 years. It is not verbatem, But close.
 

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Not sure about other 1970 SS 454s-with a 4 speed. The 454 I have has the three port fuel pump. My 454 has no charcoal canister.
I have a question? If you do not have a charcoal canister attached to your 1970- SS 454, What happens to the fuel VAPORS ?
We all know they "do not" exit to the Atmosphere, My question is, Where do the fuel vapors in the fuel tank " GO " on a 1970- LS-5 ?
The answer is ........................................................................ ?

Bob
Trivia:
The 1/4" port on the three port pump. To make my 1970 Sta.Wgn. ( Driver ) 454 Engine look like a Real factory LS-5 with the LS-5 -3 port pump.
I attached a piece of rubber hose to the fuel pump and then shoved a piece of old brake line into the other end of the rubber hose installed the correct spring clamps, Then I shoved it back into the frame rail. NOW my fuel system " LOOKS " like a factory LS-5. :thumbsup:
My FRAUD car ( with papers to prove it) SS 454 Sta. Wgn. has been driven over 38.000 miles, And so far I have not seen any fuel come out of the small line ( That is laying on the frame, and goes nowhere. beside the org. 5/16" -307 fuel line,) On my 3 port long canister fuel pump.
Also , For a driver / Cruiser, my 468 runs and operates just fine on the org. 307-5/16" fuel line.
They go out the vent in the gas cap, not sure about 70 but 69 and later had vented gas caps and with a full tank on hard take off or right turns (Camino) fuel would spill out the tank.
 

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Some more trivia from an old guy:
What does the so called term vapor lock mean? Think about this: When you boil water it turns to steam or VAPOR, When you boil Brake Fluid it turns to VAPOR. In 1962 drag racing my C/G 38 Chevy. At the end of the 1/4 I had NO BRAKES. Kill the engine and in a few seconds I had a full pedal.
Cause: Headman Headers blowing hot exhaust on brake line.
When you boil gasoline it turns to VAPOR. A 7040205 will no operate on VAPOR, Must have liquid.
So I Call my Brother in law Bill, From Mich, He says call my friend BOB, I call Bob and answer many questions for this Bob guy. He tells me on the phone the problem with my 70 454. So I do what this Bob guy tells me to do.
After I follow Bobs instructions, I now have no more Vapor Loc.
FACT: My one owner LS-5 never got hot or had vapor loc. So what changed.
I had a BAD Eaton Fan clutch.
Fact #2: 1970 " A " body Chevelles all models had an Airflow Ducted engine bay. What the hell is that? I means, All the air that enters the engine bay is FORCED to EXIT ( By road speed or by the engine powered exhaust fan.)
Fact#3: A 1970 engine bay is designed to have the Super Heated Air Exit at the rear of the Lower right & Lower left cast Iron manifolds.
Fact #4: Changing any factory under-hood installed items (rubber seals and such) , So when you re/engineer your engine bay cooling system, And you also think a lot of what this guy just is a big load of Bull Sh!T.
All this stuff about duct work and sealed off engine bay stuff and moving " X " number of cubic feet of air per min. sounds fishy.
When your home A/C or your furnace is running. Use caution !
Remove the blower belt, ( You better have " Super Heat switches working " And then lets talk about Air Flow and Duct work.
Just some trivia, From an old Guy. :thumbsup:
Bob
P.S. So you know, My B.I. law Bill was a boss at FORD the Wayne Assmb. plant for 37 years. The Bob guy I speak of was a Thermal Engineer for Chevrolet for 39 years. It is not verbatem, But close.
I do agree with a lot of that, I'm sure people will poke a bit at your wording, but I can see where you are going with it,(I'm not very good at the wording as well). But the question at hand is about modifying old cars to work with parts they weren't even designed for, so sometimes it's back to basics or just pure testing to get them right or better. So good input on the way the factory system worked but lets be honest, they didn't always work very well back then even when they were new.
 
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