Do ALL 71 Chevelles have a fuel return line? - Chevelle Tech
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  #1  
Old Nov 6th, 12, 5:18 PM
rel3rd rel3rd is offline
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Question Do ALL 71 Chevelles have a fuel return line?

Wasn't able to find any definite answer anywhere I tried looking, and hopefully this is the correct forum to ask...

I was just curious if ALL 1971 Chevelles have (or came from the factory with) a fuel return line on them?

Mine is plugged (capped off) because it has an aftermarket pump which doesn't have a port for use as a return. I don't recall any of my other Chevelles having one, but it's been quite a few years since I had one, so....
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  #2  
Old Nov 6th, 12, 5:26 PM
toofastforyou toofastforyou is offline
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Default Re: Do ALL 71 Chevelles have a fuel return line?

Quote:
Originally Posted by rel3rd View Post
Wasn't able to find any definite answer anywhere I tried looking, and hopefully this is the correct forum to ask...

I was just curious if ALL 1971 Chevelles have (or came from the factory with) a fuel return line on them?

Mine is plugged (capped off) because it has an aftermarket pump which doesn't have a port for use as a return. I don't recall any of my other Chevelles having one, but it's been quite a few years since I had one, so....
Mine has one, but I don't think it's a return line , but rather a line going to the front mounted charcoal canister. I don't think any of these carburetor equipped cars had a true return line like today's fuel injected cars...
My car also has the vent box mounted behind the rear seat...
Hope this helps,

Claude.
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  #3  
Old Nov 6th, 12, 5:50 PM
rel3rd rel3rd is offline
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Thumbs up Re: Do ALL 71 Chevelles have a fuel return line?

Quote:
Originally Posted by toofastforyou View Post
Mine has one, but I don't think it's a return line , but rather a line going to the front mounted charcoal canister. I don't think any of these carburetor equipped cars had a true return line like today's fuel injected cars...
My car also has the vent box mounted behind the rear seat...
Hope this helps,

Claude.
Thanks Claude. I guess that would explain why I couldn't find any info on a "return" line...lol.
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1971 Chevelle SS "439" 11.63@115, 1.60 sixty foot
InCar Street Cruise: http://youtu.be/MXDr5-PZouo
InCar 1/4 mile: http://youtu.be/h9sI1zcOTKE
Burning rubber: http://youtu.be/ZHMy7idIEjY
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  #4  
Old Nov 6th, 12, 10:53 PM
SamSnyder SamSnyder is offline
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Default Re: Do ALL 71 Chevelles have a fuel return line?

If your vapor lines are capped and your charcoal canister is history, make sure you have a vented gas cap. Stock with vapor lines and canister was nonvented. I used to get a massive vacuum suck when I popped the cap for fuel till I figured that out. Don't know if it would ever be enough to collapse the tank, but I imagine it was also making it harder for the pump to draw fuel.
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Old Nov 6th, 12, 11:33 PM
Hi-po SS 454 Hi-po SS 454 is offline
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Default Re: Do ALL 71 Chevelles have a fuel return line?

My 71 has one line going to the pump. Also has the canister line.
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Old Nov 7th, 12, 10:15 AM
Schurkey Schurkey is offline
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Default Re: Do ALL 71 Chevelles have a fuel return line?

Quote:
Originally Posted by rel3rd View Post
I was just curious if ALL 1971 Chevelles have (or came from the factory with) a fuel return line on them?
First Guess: Just the ones factory-equipped with A/C.

1/4" tubing, considered a VAPOR RETURN rather than the sort of return used with a fuel pressure regulator where the return line is flowing nearly all the fuel back to the tank.

The OEM vapor return is typically restricted in the fuel pump to a .060 orifice, or near that size.

Primary purpose of the OEM vapor return system was to reduce tendency for vapor lock of fuel pump due to excessive under-hood temperature.
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Old Nov 7th, 12, 11:12 AM
rel3rd rel3rd is offline
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Default Re: Do ALL 71 Chevelles have a fuel return line?

Quote:
Originally Posted by SamSnyder View Post
If your vapor lines are capped and your charcoal canister is history, make sure you have a vented gas cap. Stock with vapor lines and canister was nonvented. I used to get a massive vacuum suck when I popped the cap for fuel till I figured that out. Don't know if it would ever be enough to collapse the tank, but I imagine it was also making it harder for the pump to draw fuel.
Never have gotten any vacuum or hissing when removing the gas cap. Maybe mine is already a vented cap? It doesn't say anything on it though.

Quote:
Originally Posted by Hi-po SS 454 View Post
My 71 has one line going to the pump. Also has the canister line.
Mine definitely has two...one that is 3/8" and one that is 1/4" right next to each other on passenger side right near fuel pump.

Quote:
Originally Posted by Schurkey View Post
First Guess: Just the ones factory-equipped with A/C.

1/4" tubing, considered a VAPOR RETURN rather than the sort of return used with a fuel pressure regulator where the return line is flowing nearly all the fuel back to the tank.

The OEM vapor return is typically restricted in the fuel pump to a .060 orifice, or near that size.

Primary purpose of the OEM vapor return system was to reduce tendency for vapor lock of fuel pump due to excessive under-hood temperature.
You may be on to something Schurkey. My car is factory AC car and I also found this replacement pump just now...which definitely has a return/vapor line on it.

http://www.ss396.com/mm5/merchant.mv..._Code=FUELPUMP

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1971 Chevelle SS "439" 11.63@115, 1.60 sixty foot
InCar Street Cruise: http://youtu.be/MXDr5-PZouo
InCar 1/4 mile: http://youtu.be/h9sI1zcOTKE
Burning rubber: http://youtu.be/ZHMy7idIEjY
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  #8  
Old Nov 8th, 12, 3:25 PM
SamSnyder SamSnyder is offline
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Default Re: Do ALL 71 Chevelles have a fuel return line?

Rather than vapor lock issues, I think the vapor lines are primarily to reduce emissions into the atmosphere from evaporation, which is why the gas tank has a nonvented, i.e., sealed cap. The system works by sucking fumes out of the gas tank, through the vapor canister, into the intake, according to specified parameters (mostly on startup I think). I've read somewhere that a parked '65 Mustang emits more pollution just sitting there than a new Honda does while running.
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Old Nov 8th, 12, 4:30 PM
Schurkey Schurkey is offline
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Default Re: Do ALL 71 Chevelles have a fuel return line?

Quote:
Originally Posted by SamSnyder View Post
Rather than vapor lock issues, I think the vapor lines are primarily to reduce emissions into the atmosphere from evaporation,
Define "vapor lines".

The vapor return plumbing from fuel pump back to the tank is ABSOLUTELY for reduction of vapor lock.

The plumbing from tank to charcoal canister to carb/throttle body inlet is for evaporative emission reduction.
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