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Customs Ground Clearance Fuel Tank

Discussion in 'The Hokey Ass Message Board' started by FAKKY, Jan 13, 2019.

  1. FAKKY
    Joined: Sep 9, 2016
    Posts: 180

    FAKKY
    Member

    Whats generally accepted for ground clearance on fuel tank.

    Reason I ask is deciding behind or in front of axle. Seems like for the behind the rear axle option - as long as its above the rear diff (when the diff lead springs is compressed on top of a jack) .... no issues ?

    Same for front ?
     
  2. F&J
    Joined: Apr 5, 2007
    Posts: 13,177

    F&J
    ALLIANCE MEMBER

    A hamber lost his mid 30s mopar coupe to total fire loss from a rear wheel fell that off, and the tank dragged on pavement. It was a poly tank as I recall, but a sheetmetal tank would have ground through at those highway speeds he was traveling that moment.

    The term "scrub line" when building, is when tire goes flat and nothing should touch the pavement, including things like suspension parts and trans crossmember as well, not just the fuel tank
    .
     
  3. BamaMav
    Joined: Jun 19, 2011
    Posts: 3,254

    BamaMav
    Member
    from Berry, AL

    Nothing should hang lower that the bottom of the rear wheel rim. Higher is better.
     
  4. FAKKY
    Joined: Sep 9, 2016
    Posts: 180

    FAKKY
    Member

    So higher than the rear diff and higher than the rear wheel rim (bottom) .... coincidently thing they are about the same.

    Side question ..... if I wanted to relocate the fuel tank to the other side of the truck ........ any concerns in running an extended fill neck pipe over the top of the driveshaft ..... closer to the rear axle ? Havent seen people do this ...... but cant think of a reason not too as even when fully loaded on travel in suspension - the driveshaft cant hit .....

    (reason is using an offset 8.8 explorer rear end for a better braking/strength unit). But makes a fuel tank tight on the passenger side.

    Guessing weight/balance will be an issue with driver/fuel on same side ?
     
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  5. FAKKY
    Joined: Sep 9, 2016
    Posts: 180

    FAKKY
    Member

  6. gene-koning
    Joined: Oct 28, 2016
    Posts: 1,309

    gene-koning
    Member

    The fuel tanks on both my coupe and my new truck are both on the driver side, and both are inside the frame and ahead of the rear axle. It adds difficulty making a dual exhaust, but I have no concerns about the tank dragging on the ground. Both tanks are 16 gal. Pic of the frame under the "new" truck. The coupe is similar. Gene
     

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  7. The tank on my Fargo is inside the frame on the drivers side, no issues


    Sent from my iPhone using H.A.M.B.
     
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  8. FAKKY
    Joined: Sep 9, 2016
    Posts: 180

    FAKKY
    Member

    Thanks guys !!
    I never like to assume as I generally find out I'm wrong about something .........

    So if it had to go onto drivers side for clearance ........ just run the fuel tank intake tube to the neck filler over the top of the driveshaft --- to other side ---- but high enough to not be able to be hit my driveshaft under axle compression ?

    Rather not relocate the filler ..... but again .. *shrug*
     
  9. F&J
    Joined: Apr 5, 2007
    Posts: 13,177

    F&J
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    In case you didn't know already, you need the large venting hose run to the filler neck that lets air out of the tank during filling. The only negative thing I can think of with a longer filler pipe setup, would be the rare event where you stop to fill the tank up, (it sure will be very full to react with the nozzle trigger), but then you park a long time at a place right after filling on a hot Fla summer day.... and then the gas will expand & overflow as the gas was cooler underground.
     
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  10. gene-koning
    Joined: Oct 28, 2016
    Posts: 1,309

    gene-koning
    Member

    Both of mine have the gas fill on the driver side as well. Its not that hard to relocate the gas fill door, and patch the location it used to be in. My coupe used to gave the gas fill in the rear fender, now its behind the drivers door. It shows pretty clearly in this picture. I cut a section of metal around the gas door, cut a hole in the side of my car, then welded the gas door in place. I used the piece I cut out to fill the old gas fill hole. Gene
     

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  11. FAKKY
    Joined: Sep 9, 2016
    Posts: 180

    FAKKY
    Member

    Thanks guys.
    Good tips and input.
     
  12. FAKKY
    Joined: Sep 9, 2016
    Posts: 180

    FAKKY
    Member

    Actually just clarifying this ........ I thought I understood this ... but :)
    Its obviously just a vent to relieve pressure as you say. But then most custom tanks come with a vent of some sort and some have two.

    A rollover vent
    And a tank vent.

    Also a remote vent like https://www.summitracing.com/parts/...IMqfEzY-92QWioxNRSG51mUGCAh2FtwIaAlxaEALw_wcB


    So guessing the rollover vent is exactly that -- vent under normal circumstances and close when you upside down.

    But question is ...... if you already have the vent in the filler neck tubing ....... do you need these other vents ?
     
  13. Bandit Billy
    Joined: Sep 16, 2014
    Posts: 5,353

    Bandit Billy
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    ^^^^A gas tank has to be vented either with an external vent like you mentioned above or a vented cap. As the fuel leaves the tank and is swallowed up by your carbs an unvented tank will actually collapse (implode) unless your car dies first from a vapor lock because it cant replace the volume of the dissipating gas with air to fill the newly vacated space. If the gas cap is non vented, and you are running a vent tube inside the filler tube only, you have no vent.

    The gas tank vent should be mounted higher than the filler, vented to the atmosphere (not the inside of your car) and have roll over protection. I prefer an external vent over a vented cap as my tanks are painted at the filler neck and I'd like to keep the paint on there for as long as possible.
     
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  14. F&J
    Joined: Apr 5, 2007
    Posts: 13,177

    F&J
    ALLIANCE MEMBER

    The vent or purge hose in the neck, only is there to let the air out of tank ...that air is being replaced by fuel during refilling.

    it provides a way for that air flow to get past the gas station filler nozzle tip, so that the nozzle won't keep tripping "off" like when a tank is full of fuel. If that purge hose is not there, it will take forever to fill the tank. That hose is at least 5/8" ID , most are larger than that. You really need it as your filler will now travel over to the other side, making it very difficult to fill the tank without that purge "vent" hose.
     
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  15. FAKKY
    Joined: Sep 9, 2016
    Posts: 180

    FAKKY
    Member

  16. Atwater Mike
    Joined: May 31, 2002
    Posts: 9,700

    Atwater Mike
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    Interesting line here, as the Calif Vehicle code jumped on this and interpreted it to their own advantage, so to 'ticket and fine' lowered cars in the late '50s:
    "No part of any vehicle shall be lower than the bottom of the highest rim."
    Cops were pulling over everything raked, with 'Big-n-Littles: Cop would take his flashlight, put the 4,5" lens against the outer rear tire sidewall. Slide it up and down, for another 1.5 inches...(8.20 X 15) then proceed to the FRONT of the vehicle, slide the light under...Anything that was CLOSE got ticketed!
    An angry cop 'rammed' his flashlight under my '48 Cad, busted the lens on the crossmember. I laughed, then he was ready to adorn me with bracelets!
    'Letter of the Law'! Argument that a blowout in rear couldn't drop the front? Deaf ears!
    Some folks never heard of this nonsense. HAMB history.
    In order not to wander off the subject of this thread... 'Tanks' for reading.
     
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