Fuel pump - Chevelle Tech
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post #1 of 13 (permalink) Old Feb 27th, 20, 12:01 PM Thread Starter
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Fuel pump

my ls5 car the fuel pump isn't doing well I ordered a summit brand mechanical pump not thinking my car has two lines coming from the tank and the new pump will only have one line going into it. question is should I send the pump back and just get a stock style or change the sending unit to a single line and not use the return thanks

1970 LS-6/M22 no stripe Monaco Orange
1970 LS-5/M22 no stripe Tuxedo Black
1987 Chevy K20 with 496
1986 GMC k3500 454
1986 Chevy K30 454
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post #2 of 13 (permalink) Old Feb 27th, 20, 3:05 PM
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Rick
 
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Re: Fuel pump

If it is street and near stock, I would get the stock replacement.
I do not think Chevy put return lines on with mechanical pumps. I think it was a vapor return. Hopefully some purists will chime in.


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post #3 of 13 (permalink) Old Feb 27th, 20, 3:34 PM Thread Starter
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Re: Fuel pump

Quote:
Originally Posted by mrpaticular View Post
If it is street and near stock, I would get the stock replacement.
I do not think Chevy put return lines on with mechanical pumps. I think it was a vapor return. Hopefully some purists will chime in.

its got a bigger than stock cam headers intake etc all the cars ive had in the past someone has either gotten rid of the second line or the car didn't come with it.

1970 LS-6/M22 no stripe Monaco Orange
1970 LS-5/M22 no stripe Tuxedo Black
1987 Chevy K20 with 496
1986 GMC k3500 454
1986 Chevy K30 454
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post #4 of 13 (permalink) Old Feb 27th, 20, 4:50 PM
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Re: Fuel pump

If you have a return line I would try to use it. I believe it returned from the fuel filter back then on certain engines. It helps with vapor issues for a street car. The fuel pump was the same as far as I know.

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post #5 of 13 (permalink) Old Feb 27th, 20, 4:57 PM
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Re: Fuel pump

https://www.chevelles.com/forums/13-...ical-pump.html

some reading.

If you have a bunch of rubber fuel line get rid of it and run steel line.
I used to think there was no difference and then i checked fuel pressure at the carb. 5PSI.
I then removed the 4 feet or so of 3/8" rubber fuel line throughout the system and replaced it with steel 3/8" line.

Fuel pressure at the carb went to 7.5 psi.
Eye opener.
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post #6 of 13 (permalink) Old Feb 27th, 20, 5:28 PM
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How ‘bout rubber w/SS braid over it ?
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post #7 of 13 (permalink) Old Feb 27th, 20, 5:58 PM Thread Starter
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Re: Fuel pump

the car still retains the steel line from the back of the car to the front every high performance pump I've found only has two fittings on them I have a single line sending unit I could eliminate the 1/4 line but id like to use it. i'm confused as to what that one person was saying tapping into the carb for a return.

1970 LS-6/M22 no stripe Monaco Orange
1970 LS-5/M22 no stripe Tuxedo Black
1987 Chevy K20 with 496
1986 GMC k3500 454
1986 Chevy K30 454
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post #8 of 13 (permalink) Old Feb 27th, 20, 6:01 PM Thread Starter
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Re: Fuel pump

i'm also in the middle of building a 496 for the car so i'll need to address this eventually anyhow

1970 LS-6/M22 no stripe Monaco Orange
1970 LS-5/M22 no stripe Tuxedo Black
1987 Chevy K20 with 496
1986 GMC k3500 454
1986 Chevy K30 454
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post #9 of 13 (permalink) Old Feb 27th, 20, 6:29 PM
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jeff
 
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Re: Fuel pump

Run the regular line to the carb install a T fitting in the line and stick the return line on the T but install a regulator on that return line.
Set it at say 7 PSI if you want 7PSI at the carb.. anything over 7 goes back to the tank if your return goes to the tank.

I remember years ago running oldsmobile 455's you could get the dual line pump or the single line pump.
We would always get the dual line and plug the small extra one.
One old guy said you get just a little more PSI than the single line pump that way.

I never tested it ..My Olds had the return going to the tank. I just plugged it.
No issues for the 100,000+ miles I drove it. Sold it to sister-in-law she never had any issues.
Except fuel mileage
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post #10 of 13 (permalink) Old Feb 27th, 20, 6:48 PM
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Re: Fuel pump

My `72 El Camino has the return line running from the fuel filter. I don't know if that`s the way it was originally but it works fine.
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post #11 of 13 (permalink) Old Feb 27th, 20, 8:14 PM
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Re: Fuel pump

I do not know about your 1970-LS-5. My LS-5 has the two line fuel pump.
Why the two line fuel pump? It ia a vapor line FROM the tank. In 1970 the 454 Chevelle had a " 100% " CLOSED Emission System ". WADDA, YA mean?
ALL--Engine fumes--Fuel Fumes--Were entered into the engine and after the fumes & Emission gasses were burned off,, They would EXIT the tailpipe.
The fuel tank fumes on my 1970 LS-5/M-22 El Camino are vented into the 1/4" steel line at the fuel tank and then are pumped ( via, two line fuel pump) into the 7040205 Q-Jet to be burned off and sent into the atmosphere, VIA the tail pipe.
If you look at a correct 70-454,,, Engine fumes from the left side valve cover......... Where do they go?... Right side valve cover, Where do the fumes go? Also, Some 70s had Charcoal cannisters, Located engine bay, behind seats,.
Also: Do you need to operate you engine with the two line fuel pump, " NO ". Just so you know... On my FAKE//FRAUD--1970 SS 454 Sta. Wgn. I have the O.E.M. , long cannister fuel pump, WELL, What about the 1/4" vapor line?? So my FAKE SS looks real... I got a piece of brake line about 8" long, I soldered the end shut, Attached a piece of 1/4" fuel hose to the pump and then stuck 8" piece of 1/4" steel brake line with the end soldered shut, And stuffed it into the frame beside the stock 5/16" fuel line.
So when you look at my FAKE LS-5-SS,,,, BUBBA says,,, YEP its a real LS-5,,,, Its got the two line fuel system.
Its the joke about the " Book & Cover". In the early days of the " NEW EMISSION SYSTEMS",,,, Late 60s & Early 70s---- G.M.--Ford & MOPAR were ALL OVER the place with emission equipment !
The beginning of the end is near with " Horsepower "--late 60s & early 70s...........
Bob
P.S. Fifty years ago this month, I ordered my LS-5/M-22 at Sahli, Chevrolet, in Beaver Falls,Pa. The second week of March.. It will be " 50 " years old.


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1970 ( FRAUD) SS 468 Station Wagon - Driver.
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post #12 of 13 (permalink) Old Feb 27th, 20, 10:38 PM
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Re: Fuel pump

Trivia: Be careful when buying the long canister fuel pump. WHY?
Some Corvettes of that era use the long two line fuel pump. The steel line to the Q-Jet will NOT LINE UP using the Vette Pump. the fitting on the Corvette pump in in a different location than the Chevelle pump.
I was about to start bending my lines,...... Then I said this is Bu!! Ship! Just make sure its a Chevelle pump.
Bob


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1970 ( FRAUD) SS 468 Station Wagon - Driver.
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post #13 of 13 (permalink) Old Feb 28th, 20, 8:00 AM Thread Starter
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Re: Fuel pump

I bought a aftermarket two line pump I knew the 1/4 line was for vapor and I really don't need it but the car has the two line sending unit which I had just replaced in the fall so I don't know what to do with the unused vapor line

1970 LS-6/M22 no stripe Monaco Orange
1970 LS-5/M22 no stripe Tuxedo Black
1987 Chevy K20 with 496
1986 GMC k3500 454
1986 Chevy K30 454
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