Fuel Pump: 2 Line VS 3 Line.

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kygaca

Apprentice
Jul 3, 2018
52
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Annapolis, MD
Hey y'all, background info:
1972 Olds 350 being put into a 1987 El Camino. The El Camino has three fuel lines, and an in tank pump. On the new engine, I have installed a 2 line mechanical fuel pump.
My question:
What are the three line vs two line uses? Without having to buy and install a different pump, what modifications may I have to do to use the two line pump in the 3 line car? How would I remove the in tank pump and set up the tank for a mechanical two line system?
 

69hurstolds

Geezer
Supporting Member
Jan 2, 2006
8,089
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AC DELCO 40712 aka GM P/N 6470330 or equivalent aftermarket.

CARTER M6109
DELPHI MF0006

Just make sure to get the 3 line version.
 
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MrSony

Geezer
Nov 15, 2014
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Des Moines, Iowa
3 lines. as said, vent, return, feed. not all had all 3.
 

Ribbedroof

Comic Book Super Hero
Supporting Member
Jan 4, 2009
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Wellston, OK
Sounds like the Camino was injected, which is likely going to be more pressure than a mechanical pump can handle. Either use the in-tank pump and regulate the pressure down to 6 pounds, or pull the pump/sender and install an earlier sender without pump for a carburated application, using the mechanical pump on the Olds engine.
 
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xylorex

Master Mechanic
Aug 2, 2018
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New Orleans, LA
Last edited:
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Oct 14, 2008
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I have used these in both 2 and this 3 line with good results. https://www.summitracing.com/int/parts/crt-m6109/make/oldsmobile You can use the inline tank and regulator or add a higher pressure pump for an aftermarket EFI. With a 454 TBI with factory Qjet intake adapter, 307 CCC distributor and even just a sbc 350 prom or whole computer, you can run TBI on your Olds 350, especially if you are running the stock cam. I can tell you, the timing needs advanced about 20 degrees over stock to run the sbc swirl port tune.
 

herb

Not-quite-so-new-guy
Feb 10, 2018
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9
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the original factory 3 line purpose is to help keep the fuel supply cooler,,

,less knocking ,less boiling of fuel in stop and go driving
and not pressure change related,,,however,, corvette and hi-po 350s pumps did have a slight pressure increase as in the old 2 line pumps,,
also,,the pumps exit -entry line direction vary ,per application , which would mean a new steel line to carb,, if you mis-order..
so better off going to napa-autozone, oriellys etc, for fast return,,turnaround,,visual inspection,, and if not in stock, you can look at their screen for pics of pump bottom to gauge outlet directions...
 
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