Why do people block fuel return lines??
Thread Starter
Pro
Joined: Oct 2006
Posts: 542
Likes: 3
From: Vilnius, Lithuania
Why do people block fuel return lines??
What is the reason, why some owners block the fuel return line on their Corvettes?
I previously had '73, now I have '68, and they both came from US with fuel return lines blocked (return line disconnected from the bottom of fuel pump and both ends have a screws inserted). Should I leave it the way it is on my '68? Now the engine is running without any problems.
Thanks...
I previously had '73, now I have '68, and they both came from US with fuel return lines blocked (return line disconnected from the bottom of fuel pump and both ends have a screws inserted). Should I leave it the way it is on my '68? Now the engine is running without any problems.
Thanks...
Safety Car
Joined: Oct 2000
Posts: 4,282
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From: Lake Wylie, South Carolina
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Melting Slicks
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Drifting
Joined: Aug 2005
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From: League City TX
What is the reason, why some owners block the fuel return line on their Corvettes?
I previously had '73, now I have '68, and they both came from US with fuel return lines blocked (return line disconnected from the bottom of fuel pump and both ends have a screws inserted). Should I leave it the way it is on my '68? Now the engine is running without any problems.
Thanks...
I previously had '73, now I have '68, and they both came from US with fuel return lines blocked (return line disconnected from the bottom of fuel pump and both ends have a screws inserted). Should I leave it the way it is on my '68? Now the engine is running without any problems.
Thanks...
On a Quadrajet, fuel can siphon out of the float bowl past the needle and seat leaving you with an empty carb when you go to crank the car after it has sat for a while. Disconnecting the return should stop that problem because the fuel cant drain back through the return. Of course it can cause other problems too.
I would recommend reconnecting it and seeing how it works when set up correctly.
Le Mans Master
Joined: Jun 2005
Posts: 5,447
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From: Syracuse NY
) has a paper on building a fuel system with a return line. BarryK might have it on his site as well.PM me if you don't know where Lars posts these days.
Team Owner
Joined: Apr 1999
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
I've always used wood 1/2 to 1 inch four hole spacers on single plane intakes.
As for how to route a return. I've done several BB cameros at the shop. Run a small diameter return like 1/8th from the back of fuel log to the tank. For stock type tanks you drill correct size a hole high up on the filler neck Feed the return line down into the bottom of the tank.
On the back of the fuel log you use a 1/8th flare to A/N fitting. The problem is depends on how much fuel flow your pump has. Generally these are all electric pumps with a high Gallon rating. If you can't get your regulator to get up to desired pressure you have to restrict even a 1/8th inch line. A holley jet is a very good restrictor device. I think my last job used a 70 jet size. At 7 PSI that is still enough flow to keep cold fuel in the fuel log -NO Vapor Lock and the pumps last much longer because they are not pumping against a wall.
Safety Car
Joined: Oct 2000
Posts: 4,282
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From: Lake Wylie, South Carolina
Thanks! Yes he posted a response with a pic on another forum. I was not aware of the tech paper though. I will have to look into it.
Racer
Joined: Jan 2004
Posts: 273
Likes: 0
What is the reason, why some owners block the fuel return line on their Corvettes?
I previously had '73, now I have '68, and they both came from US with fuel return lines blocked (return line disconnected from the bottom of fuel pump and both ends have a screws inserted). Should I leave it the way it is on my '68? Now the engine is running without any problems.
Thanks...
I previously had '73, now I have '68, and they both came from US with fuel return lines blocked (return line disconnected from the bottom of fuel pump and both ends have a screws inserted). Should I leave it the way it is on my '68? Now the engine is running without any problems.
Thanks...
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
I agree. The ones I have seen blocked were done so because the fuel pump was on its last leg and needed replaced. I think it was pretty common back then when a car would not run higher speed the first thing guys would do was to put a clamp on the return line and if that helped it was time for a new fuel pump or fuel filter in the carb. Problem was some guys considered blocking off the return and actual repair. And one other thing about blocking it I believe the added pressure will lift the fuel filter off its gasket allowing unfiltered fuel into the carb.