70 b body gas tank vent lines?

Fuel and Air Systems

  1. luis9995

    luis9995 Well-Known Member

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    My 70 b body leaked a little gas when parked on incline. Of the two lines at the end one goes into the trunk the other is small. Would it be ok if I block off the small one ?
     
  2. Jerry Hall

    Jerry Hall Well-Known Member

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    One is supposed to be a vent line and one is a return line. If you're not using a return line then cap it off. 70 was supposed to have a 1/4" return line.
     
  3. PurpleBeeper

    PurpleBeeper Well-Known Member

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    Hmmmm, my '70 never had a return line, so maybe that's a California emission thing???

    I believe the big loop that goes into the trunk is an expansion tube or something like that (?). The little short line, about 6" long & bent, is the tank vent. It is attached with one screw & a tiny bracket at the rear shock absorber upper bracket.

    I would not block that one off since in '70 the gas caps are non-vented. Under high fuel demand, it could cause the engine to starve for fuel and/or collapse the gas tank. If it's THAT one that's leaking, just check the hose and/or bend another one (in my opinion). If you do plug it off, make sure you have a vented gas cap.

    Hope This Helps!
     
  4. 440+6

    440+6 FBBO Gold Member FBBO Gold Member

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    The one that goes into the trunk is a vent for the front of the tank the little j-shaped one is a vent for the back of the tank, if you have a return line it would be in the gas sending unit, six packs and hemi had the return

    I capped both but I made a vented gas cap
     
  5. hsorman

    hsorman FBBO Gold Member FBBO Gold Member

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    And California cars had a return too. The CA cars have a "tube" in the trunk on the passenger side. This is a fuel capture device that has 5 lines coming out from it. One connects to the engine, and the others go to the special California gas tank.
     
  6. 440+6

    440+6 FBBO Gold Member FBBO Gold Member

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    Yes California tanks are a whole nuther monster with that big tube in the trunk and all the lines going into it
     
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    • Jerry Hall

      Jerry Hall Well-Known Member

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      My Superbird 440-4bbl has a return line and 440+6 is right the return line is at the sending unit. The line that goes into the trunk is the vent line. I guess my repro tank has no other vent, of course I finished its restoration in 04.
       
    • dadsbee

      dadsbee FBBO Gold Member FBBO Gold Member

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      My 440-4 Bird has a return line.. and it returns in the sender. Vent line to trunk/frame rail and another small vent to shock mount. Vents are the same as my '69 Bee which doesn't have a return line to the sender.

      As noted by 440+6 the trunk vent is for the front of the tank and the small vent to shock mount bulkhead is for the rear of the tank. Maybe the OP's lines are hooked up backwards and the little vent is hooked to the tank front line.

      Tank vent tube closest to sender should be the trunk line (front of tank) and furthest over the short vent tube that connects to the internal tube to the rear of the tank.

      beerestoration2018 157.JPG beerestoration2018 158.JPG beerestoration2018 163.JPG
       
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      • Bill Monk

        Bill Monk FBBO Gold Member FBBO Gold Member

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        The long vent tube that goes into the trunk should be attached to the short line in the tank. The short "J" tube connects to the long line in the tank. Some of the reproduction tanks reversed the tubes in the tank so if this is not original, that could be the issue. The only way to know for sure is to take a light and look in the tank. I guess you could reverse what you have and see if that cures the problem.
        The car has a non vented cap. Don't plug those vent lines unless you can find a vented cap that will work!
         
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        • BubbaMope

          BubbaMope Well-Known Member

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          I have the California gas tank here in Bossier City, Louisiana... I'm fixing to drop and replace my original tank. I've been wondering where all those hoses go. I bought about 20 feet of 1/4 and 3/8s fuel line to replace all that crap! I'm about to make the jump to TB Fuel Injection. I'll be asking questions about that project.
           
        • hsorman

          hsorman FBBO Gold Member FBBO Gold Member

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          The CA tanks have four vent lines that connect to the trunk mounted cylinder. These are short runs just between the edge of the tank and the four lines that protrude from thee cylinder. The other cylinder line connects to the breather cap on the engine, which in turn connects to the carb. Below are some pictures of my car before it was restored. Hope this helps...

          Hawk


          Engine bay (no engine) showing the vent line
          IMG_1940.JPG


          Vent Cylinder in trunk, viewed from below. The connected line is the vent from the engine. The other four go to the tank
          IMG_1780.JPG


          An original CA tank. Spectra still makes reproductions of these.
          IMG_1569.JPG

          Engine picture showing breather with vent line going to the CA Holley carb.
          IMG_0693.JPG
           
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          • BubbaMope

            BubbaMope Well-Known Member

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            Thank you! I'm looking at systems that are return and returnless. What I'm reading is the return line should pump back into the tank below the fuel level as opposed to spraying in from the top through the sender to prevent aeration. Can the vent tubes on the side of the tank be used as a return line inlet? I'm not sure if there are baffles etc. in the tank where the vent tubes go.
             
          • hsorman

            hsorman FBBO Gold Member FBBO Gold Member

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            I strongly suggest a return type if you can do it, it will keep your fuel cool. I have this type in my car now, and it has worked great. I purchased two Hemi fuel lines for my car and routed them together. One is the supply and the other is the return. I also bought a custom gas tank with an in tank fuel pump.

            Details are on my restoration thread if you would like to check it out.
            https://www.forbbodiesonly.com/moparforum/threads/hawk-rod-the-restoration.65096/

            Hawk