Fuel pump??
Thread Starter
Le Mans Master
Joined: Jan 2006
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From: GA "When I grow up, I'm gonna get a Trans Am and run from the cops". Direct quote from my 4yo son.
Fuel pump??
I need some advice on a fuel pump. Swapping my engine and will put on a new fuel pump. The ones through Summit have no provision for the return line ('80 model). I've heard of vapor lock problems when not using this line. I need at least 6psi fuel pressure according to info that came with the motor GMPP350/330 horse. Thanks
Tech Contributor
Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
If you're running a BG or a Holley carb on that engine, you can run a fuel return line off the end of the fuel inlet log, and run the line down to your frame rail to pick up the stock return line. This type of system works very well and allows you to use any pump without a return provision.
Lars
Lars
Burning Brakes
Joined: Feb 2006
Posts: 1,024
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From: AL
well, since that one was answered, how about for the case where a Mk V is installed (no provision for mech pump) on a 74 with a Q-jet? the original mech pump had a supply and vent(?) line. will it work to install a factory AC type elec pump and plug the vent(?) line? thanks
Thread Starter
Le Mans Master
Joined: Jan 2006
Posts: 5,921
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From: GA "When I grow up, I'm gonna get a Trans Am and run from the cops". Direct quote from my 4yo son.
Originally Posted by lars
If you're running a BG or a Holley carb on that engine, you can run a fuel return line off the end of the fuel inlet log, and run the line down to your frame rail to pick up the stock return line. This type of system works very well and allows you to use any pump without a return provision.
Lars
Lars
Tech Contributor
Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
Sure. Just install a "T" fitting in the line close to the carb inlet. Use the one branch of the "T" for the return fuel. I like to weld the hole in the "T" closed and then drill it out to about a .030" hole to restrict the return fuel flow a bit when using a near-stock mechanical pump. This will keep the pressure up at the carb while allowing a steady return fuel flow to eliminate vapor lock and hard starting.
Tech Contributor
Joined: Aug 1999
Posts: 14,356
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From: At my Bar drinking and wrenching in Lafayette Colorado
Originally Posted by S489
well, since that one was answered, how about for the case where a Mk V is installed (no provision for mech pump) on a 74 with a Q-jet? the original mech pump had a supply and vent(?) line. will it work to install a factory AC type elec pump and plug the vent(?) line? thanks
Burning Brakes
Joined: Feb 2006
Posts: 1,024
Likes: 1
From: AL
Electric fuel pumps don't like to be dead-headed: It increases amp draw and increases operating temperature of the pump (with a corresponding decrease in pump life). If you can install a return fuel system your electric pump will be much happier...
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Pro
Joined: Nov 2000
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From: Tucson AZ
Lars is indeed correct about a return line with an electric pump. 
Here is where I mounted my pump (body on now, everything clears good)
The line running on top of the frame is the return line. The 'T' fitting supplies return fuel to the pump for priming purposes. That compression fitting that transitions the braided line to the hard line leaked at pressure test so I now have it sleeved and flared.
This shows how I routed the supply and return lines
They terminate at frame mounted bulkhead connectors
and connect to engine mounted bulkheads via braided line.
Craig
Here is where I mounted my pump (body on now, everything clears good)
The line running on top of the frame is the return line. The 'T' fitting supplies return fuel to the pump for priming purposes. That compression fitting that transitions the braided line to the hard line leaked at pressure test so I now have it sleeved and flared.
This shows how I routed the supply and return lines
They terminate at frame mounted bulkhead connectors
and connect to engine mounted bulkheads via braided line.
Craig
Pro
Joined: Nov 2000
Posts: 594
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From: Tucson AZ
Originally Posted by S489
Craig,
what mods were required on your tank?
does return go to tank of suction side of pump?
looks good!
what mods were required on your tank?
does return go to tank of suction side of pump?
looks good!
. Owned her for 11 years and I've almost forgotten how it feels to drive it 
I drilled the tank and mounted a 6AN male for the return line to connect to:
And welded an 8AN male on the tank pickup:
I know from others experience here with high pressure fuel systems that I will have a problem with fuel pickup when the tank is less than 1/4 full. I plan on setting up another tank, with a sump, and installing it in the future.
Craig
Melting Slicks
Joined: Sep 2004
Posts: 2,412
Likes: 3
Vapor lock? Que? I've been running a mechanical fuel pump with no return line for almost a year now, no problems. I'm using a Carter Strip pump, it makes about 7psi, sometimes a little more. The Carter street pump only made about 5psi, despite what the description claims. If I were you I'd just buy the strip pump with a holley fuel pressure regulator and set it at 6spi, the regulator will have a return port built in and you can send that to your return line. You should be able to buy both for about $100.