Mech Fuel Pump
Racer
Joined: Apr 2008
Posts: 436
Likes: 2
I bought a Holley Mech pump for my ZZ454 and it only has an IN and an OUT. There isn't a provision for the return line. I couldn't find any pumps that had the provision and another forum member who has this engine used the same pump. What are my options?
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
1971 with Small block ... there are TWO OE pumps ...
3-way (in-return-out) for Quadrajet carbed L48 ...
2-way (in-out) for Holley carbed LT1
?perhaps GM engineers found Qjet required a return while Holley did not?
3-way (in-return-out) for Quadrajet carbed L48 ...
2-way (in-out) for Holley carbed LT1
?perhaps GM engineers found Qjet required a return while Holley did not?
Melting Slicks
Joined: Jan 2003
Posts: 2,712
Likes: 31
From: Shreveport LA
LA Events Coordinator
I too was looked for a 3 prong mech fuel pump and was unable to find one. I talked to a friend of mine who is a mechanic for a local Chevy dealership and he explained to me the reason for the return line (pollution control back in the day...something about the gas vapors or liquid going back to the tank....can't really remember exactly). He also told me how to properly and safely seal it off, which I did and have had no problems since (about 8 years ago).
Here's what I did: I went back from the pump far enough so the "fix" was safe. I removed the rubber line from the steel line and plugged the end (going to the tank) with a rubber plug to fit the ID of the line (I've heard of people using screws to plug the line) and hose clamp so it wouldn't leak...and then I proceeded to install my BRAND NEW HOLLEY fuel pump. I have an in-line fuel pressure gauge by the carb and I've been running 6 lbs of pressure since.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
T in the return on the line going to the carb from the pump. Use a .070 hole for the return or get a diff pump with a return.
Race Director
Joined: Jul 2001
Posts: 15,892
Likes: 42
That's incorrect- the third line has nothing to do with pollution controls. It allows recirculation of fuel through the pump to eliminate any possibility of vapour lock. Blocking off the line in order to use a two port pump is a step backwards.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
For BBC
3-way (in-return-out) fp
AC-Delco p/n 40770 , Airtex-Carter p/n 40770
---------------------------------------------------
For sbc
3-way (in-return-out) fp
AC-Delco p/n 41240 , Airtex-Carter p/n 41240
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Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,114
From: Crossville TN
While the return line wasn't specifically designed for pollution control, it did have the effect of reducing the amount of heat generated by the pump, since there was a route for 'excess' fuel to be relieved. That kept the fuel a bit cooler and reduced the tendency to have any boiling of the fuel and/or a vapor-lock situation.
Racer
Joined: Nov 2008
Posts: 315
Likes: 46
From: Chicago Illinois
3rd line
I too have changed my fuel pump to a Holley mechanical, Like FLYVIPER , 1 in and 1 out. What I did was purchase the fuel filter to a 69 it has the the extra outlet built into it, that way all I did was run a rubber fuel line to the steel return line. Threaded steel lines make a nice clean connection. This worked very well, and vapor lock is non issue on a hot day when traffic isn't moving.[IMG]/http://i818.photobucket.com/albums/zz103/WILLRIV713/Fuellines002.jpg[/IMG]
Last edited by CFD E59; Aug 17, 2009 at 03:00 PM. Reason: adding pic
Melting Slicks
Joined: Jan 2003
Posts: 2,712
Likes: 31
From: Shreveport LA
LA Events Coordinator
While the return line wasn't specifically designed for pollution control, it did have the effect of reducing the amount of heat generated by the pump, since there was a route for 'excess' fuel to be relieved. That kept the fuel a bit cooler and reduced the tendency to have any boiling of the fuel and/or a vapor-lock situation.
) and I drive in hot, humid Louisiana summers!Gonna look at the 69 fuel filter........
Racer
Joined: Apr 2008
Posts: 436
Likes: 2
1971 with Small block ... there are TWO OE pumps ...
3-way (in-return-out) for Quadrajet carbed L48 ...
2-way (in-out) for Holley carbed LT1
?perhaps GM engineers found Qjet required a return while Holley did not?
3-way (in-return-out) for Quadrajet carbed L48 ...
2-way (in-out) for Holley carbed LT1
?perhaps GM engineers found Qjet required a return while Holley did not?
Melting Slicks
Joined: Jan 2003
Posts: 2,712
Likes: 31
From: Shreveport LA
LA Events Coordinator
