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  • Gas tank vent

    I don't want an open-to-atmosphere vent because with temp changes it creates fumes, so I modified this tank vent to rest closed and wondered if I'm missing a reason why they wouldn't have this as an option for hot rodders.


    I'll post better pictures tonight, but basically there's now a spring (stolen from a holley carb) which holds the ball against the top of the vent. And before you ask, back before tank vents, the gas cap allowed pressure to escape around the seal on the gas cap - this allows breathing the other direction without fumes escaping when the tank has higher pressure inside then outside.
    Doing it all wrong since 1966

  • #2
    If I recall the vent prevents flooding and vapor lock when the pressure builds up from heat while parked.
    When driving the vent lets air in the tank to replace the gas used so the tank does not collapse.
    On the newer cars the vent goes to a charcoal canister then gets sucked into the engine while coasting controlled by vacuum now electronically by ecm.

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    • #3
      it can still breath, but it's just not always open to atmosphere. When the tank heats up, the fuel expand and some flashes to a gas - which gives the smell - my thought is by not leaving it fully open all the time, I'll slow down the evaporation and smell.
      Doing it all wrong since 1966

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      • #4
        I"ve been wanting to put a charcoal canister on one of mine, just to see if it helps that problem..
        My fabulous web page

        "If it don't go, chrome it!" --Stroker McGurk

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        • #5
          On my FJ40, I replaced all the stainless lines with ptfe lined fuel lines and that completely solved the problem.... in this case, I think I need more vent then what the cap can provide.
          Doing it all wrong since 1966

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          • #6
            IMO charcoal cans were one of the few good things the '70s emissions thing brought us, e-z to plumb and use, reduce smog, no performance penalty.
            ...

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            • #7
              Originally posted by Loren View Post
              IMO charcoal cans were one of the few good things the '70s emissions thing brought us, e-z to plumb and use, reduce smog, no performance penalty.
              I don't disagree, and Plastic one had the system - however, it's all missing on mine, so it's this.... unless it doesn't work, then it's that....

              as for smog - I think the fires have got you down, once the air clears, I know you'll be out filling it with Mopar smoke
              Last edited by SuperBuickGuy; December 12, 2017, 10:20 AM.
              Doing it all wrong since 1966

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              • #8
                The only smoke I've been filling the air with lately comes from a beater Dodge diesel, but it does a fine job of it. There's been a used pressbrake sitting in front of the Chal for some time but it's moved now so maybe next spring. Am wishing to go through the motor first, needs a couple things.

                Growing up in the downwind side of the San Fernando Valley during the worst of the L.A. air pollution period, I have a little pang of conscience every time I release a batch of unburned hydrocarbons (seems worse to me than regular old particulate matter) into the air, at least get that stuff burned good and set to some useful purpose first.
                ...

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                • #9
                  Venting a tank is easy and it will not smell like gas either most of the time.

                  1/4" hose ran above the top of the tank and put 3 loops about 4" diameter in the hose and secure it with a filter of your choice. The vapor's will be caught in the loops and no more smell.
                  Retirement is better than I thought!

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                  • #10
                    Originally posted by Loren View Post
                    IMO charcoal cans were one of the few good things the '70s emissions thing brought us, e-z to plumb and use, reduce smog, no performance penalty.
                    there is several versions too.
                    I even found my 96 truck with a bypass to goto "air cleaner"
                    now that more than half of america is suffering with what mane gets thrashed with..

                    don't need to use purge valve exclusively, there is always two options.
                    I only proved the cali version on purge valve alone is ridiculous.

                    I keep them both hooked up, the purge has computer codes, and still does what it functions.
                    Previously boxer3main
                    the death rate and fairy tales cannot kill the nature left behind.

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