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#1 |
Senior Member
![]() Join Date: Nov 2022
Location: Kansas City
Posts: 497
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Gas vent tube?
Hi. Is this fuel line supposed to be like this?
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1971 C10 manual cab. 76 4x4 chassis. Cut short frame. Carbureted Blueprint 350, automatic 700r4. ~ James |
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#2 |
Registered User
Join Date: Jan 2001
Location: Orem, Utah
Posts: 8,022
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Re: Gas vent tube?
There are no fuel lines that are open to the atmosphere...
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I have sworn upon the altar of God, eternal hostility against every form of tyranny over the mind of man. - Thomas Jefferson |
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#3 |
Not a bad nut after all..
Join Date: Dec 2000
Location: ND
Posts: 1,760
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Re: Gas vent tube?
Are these fuel lines on the underside of the gas tank?
I would guess one could be supply and one could be return, but I've never seen a return on the bottom.
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'05 Chevy 2500HD 4x4 '72 GMC LWB 4x2 driver '72 Chevy LWB 4x4 plow truck '71 Blazer 4x4 driver '70 GMC LWB trailer |
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#4 |
Senior Member
![]() Join Date: Nov 2022
Location: Kansas City
Posts: 497
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Re: Gas vent tube?
Yup the one closest to the tank runs through the floor and then into the front of the truck. The one going through the floor closest to the seat runs through the floor and is cut off. 8n the cab in the cab it runs to the roof in a cavity and then returns to the tank.
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1971 C10 manual cab. 76 4x4 chassis. Cut short frame. Carbureted Blueprint 350, automatic 700r4. ~ James |
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#5 |
Registered User
Join Date: Nov 2009
Location: Sherman, ME
Posts: 2,373
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Re: Gas vent tube?
That vent line (that currently ends off under the floor) originally ran up to a charcoal vapor recovery canister in the engine compartment. The canister stores up gas fumes that evaporate from the tank. A purge line ran from the canister to the carburetor to draw out the fumes (and burn them in the engine) when running.
The loop that runs up inside the cab is a liquid-vapor separator to keep any liquid gasoline from making it's way into the vent line / canister. |
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#6 | |
Senior Member
![]() Join Date: Nov 2022
Location: Kansas City
Posts: 497
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Re: Gas vent tube?
Quote:
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1971 C10 manual cab. 76 4x4 chassis. Cut short frame. Carbureted Blueprint 350, automatic 700r4. ~ James |
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#7 |
Senior Member
![]() Join Date: Feb 2022
Location: Ca
Posts: 715
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Re: Gas vent tube?
I am all for pollution control but I think this venting system is some what over doing it relative to net gain in environment protection given how dirty these motors actually run. Unless doing a full restoration,I would cap the line, run a vented filler cap and call it a day. If you are already running vented cap then this system is worthless. If you are running nonvented cap you can convert by removing the spring and rubber valve. Though this mod to the cap may be an issue in a roll over as it could leak fuel.
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#8 | |
Senior Member
![]() ![]() Join Date: Feb 2009
Location: Northern Nevada
Posts: 7,385
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Re: Gas vent tube?
Quote:
That truck probably wasn't equipped with a RETURN line, they started that business in 72. Your vent line appears to be wide open, and perhaps a tad dangerous? I recall someone recommending a valve of sorts for that situation, though post 7 looks like a good idea.
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Tony 71 Custom Deluxe, SWB, 2WD, 402, A/C. I developed an assembly guide (kit) for restoring this truck from the ground up, complete with details including full hardware descriptions. Much of the info. applies to all 67-72 GM. My build thread, with some info. about the assembly kit https://67-72chevytrucks.com/vboard/...d.php?t=730025 |
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