Fuel return line
Thread Starter
Instructor
Joined: Nov 2023
Posts: 166
Likes: 28
From: Western new York
Thanks for your input guys, Was reading post about Hard starting when the engine was hot. One of the Problems was vapor lock, and the fuel return line helped solve that, Noticing I have a fuel return line was looking to prevent future problem!
Dr. Detroit
Joined: Mar 2012
Posts: 10,095
Likes: 4,026
From: New Braunfels Texas
But if you want one.....a real easy way is the GF-432 AC Delco filter for L46 350/350 application.....just cut and flare your line to it.......the 180 degree hard return line is available through Vette vendors.....it is closer to the carb too.....
Jebby
Race Director
Joined: May 2006
Posts: 18,692
Likes: 2,572
They were only used on Quadrajet applications to prevent vapor lock. Holley fuel bowls are separated from main body by two gaskets, metering block and float bowl so heat transfer from main body would be less than Quadrajet design where fuel is stored in main body.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
Safety Car
Joined: May 2001
Posts: 4,749
Likes: 1,642
From: Fairfax Virginia
Hello there JebbySan,
Just out of curiosity, Why do they run the fuel lines up front to just behind the radiator in all the hot air? It would seem that putting the fuel pump there alone is bad enough but to have hard metal lines and other parts right in the path of all the HOT air coming out of the radiator seems like a "bad idea" and this is why I tried to re-route them to keep them away from heat.
On the Holley Stealth Sniper the fuel comes into the throttle body on the passengers side either front or back. I don't have a return line with my Sniper system. I put a DEI tube insulation over the gasoline lines and then put a Fireproof jacket over the last 10 feet before the throttle body. So when I ran the fuel lines I ran them into the engine compartment from the rear of the right side of the engine. Having the entire fuel line insulated was done because cooler fuel is denser fuel.
Cooler Air, Cooler Fuel and you have a happy 12.25-1 Compression engine that can be driven on the roads of America. Only during the hottest months of the year do I have to activate my Water/methanol Injection system. I am setting up the Sniper to control the water/methanol injection system automatically.
In the 32 years I have had this C3 I have NEVER had it vapor lock or refuse to start when hot.
Just out of curiosity, Why do they run the fuel lines up front to just behind the radiator in all the hot air? It would seem that putting the fuel pump there alone is bad enough but to have hard metal lines and other parts right in the path of all the HOT air coming out of the radiator seems like a "bad idea" and this is why I tried to re-route them to keep them away from heat.
On the Holley Stealth Sniper the fuel comes into the throttle body on the passengers side either front or back. I don't have a return line with my Sniper system. I put a DEI tube insulation over the gasoline lines and then put a Fireproof jacket over the last 10 feet before the throttle body. So when I ran the fuel lines I ran them into the engine compartment from the rear of the right side of the engine. Having the entire fuel line insulated was done because cooler fuel is denser fuel.
Cooler Air, Cooler Fuel and you have a happy 12.25-1 Compression engine that can be driven on the roads of America. Only during the hottest months of the year do I have to activate my Water/methanol Injection system. I am setting up the Sniper to control the water/methanol injection system automatically.
In the 32 years I have had this C3 I have NEVER had it vapor lock or refuse to start when hot.
Last edited by ctmccloskey; Feb 4, 2024 at 08:22 PM.
Dr. Detroit
Joined: Mar 2012
Posts: 10,095
Likes: 4,026
From: New Braunfels Texas
Hello there JebbySan,
Just out of curiosity, Why do they run the fuel lines up front to just behind the radiator in all the hot air? It would seem that putting the fuel pump there alone is bad enough but to have hard metal lines and other parts right in the path of all the HOT air coming out of the radiator seems like a "bad idea" and this is why I tried to re-route them to keep them away from heat.
On the Holley Stealth Sniper the fuel comes into the throttle body on the passengers side either front or back. I don't have a return line with my Sniper system. I put a DEI tube insulation over the gasoline lines and then put a Fireproof jacket over the last 10 feet before the throttle body. So when I ran the fuel lines I ran them into the engine compartment from the rear of the right side of the engine. Having the entire fuel line insulated was done because cooler fuel is denser fuel.
Cooler Air, Cooler Fuel and you have a happy 12.15-1 Compression engine that can be driven on the roads of America. Only during the hottest months of the year do I have to activate my Water/methanol Injection system. I am setting up the Sniper to control the water/methanol injection system automatically.
In the 32 years I have had this C3 I have NEVER had it vapor lock or refuse to start when hot.
Just out of curiosity, Why do they run the fuel lines up front to just behind the radiator in all the hot air? It would seem that putting the fuel pump there alone is bad enough but to have hard metal lines and other parts right in the path of all the HOT air coming out of the radiator seems like a "bad idea" and this is why I tried to re-route them to keep them away from heat.
On the Holley Stealth Sniper the fuel comes into the throttle body on the passengers side either front or back. I don't have a return line with my Sniper system. I put a DEI tube insulation over the gasoline lines and then put a Fireproof jacket over the last 10 feet before the throttle body. So when I ran the fuel lines I ran them into the engine compartment from the rear of the right side of the engine. Having the entire fuel line insulated was done because cooler fuel is denser fuel.
Cooler Air, Cooler Fuel and you have a happy 12.15-1 Compression engine that can be driven on the roads of America. Only during the hottest months of the year do I have to activate my Water/methanol Injection system. I am setting up the Sniper to control the water/methanol injection system automatically.
In the 32 years I have had this C3 I have NEVER had it vapor lock or refuse to start when hot.
My L-88 Air Chamber hood on my 72' is definitely helpful.....I don't have it sealed but the air filter is up in the chamber......
Jebby
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
My dads 69' 427/390hp has the return line. It comes out of the fuel filter and returns back to the line on the frame.
I think it is a q-jet thing why they have them.
I say that your car had to come oem with the AC Delco 2 output and one input fuel pump with the return line to the tank. Good hearing from you again!
The 68 427/390 has the return line off the "big" filter that attaches to the smog pump bracket. A lot of folks who discarded the smog pump just have the filter hanging there. The fuel pump has an inlet hose that then has a hard line going to the filter and an outlet line going to the carburetor. The vapor line makes a complete 180* turn and goes back down to the main line near the fuel pump. Some of the vendors have great pictures of the line setup (Doc Rebuild for one.)
Q-Jet cars got the return line,..Holley cars didn't. The fuel return line was used to prevent vapor lock. This return line allows the fuel to circulate in a loop to prevent vapor lock. I'm guessing that since Holleys moved more fuel, perhaps VL wasn't a problem,..but don't know.
On the other frame rail, 1970+ cars had the EVAP line than ran from the fuel tank and eventually to the carb. This line didn't carry fuel,..only fumes from venting the tank.
This filter was only used on corvettes in 1968 and 1969 (It was also used in Camaros, maybe other chevys of similar years). In 1970 and later the fuel return line came right off the fuel pump. So a 1968/69 fuel pump only has one outlet, while a 1970 and later fuel pump has 2 outlets.