Hot Rod article on 70 Barracuda trunk floor

Mopar Body and Trim

  1. azaustin

    azaustin FABO Gold Member FABO Gold Member

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    Today’s online posting in Hot Rod had a how-to on replacing a 1970 Barracuda trunk floor. They emphasize properly bracing the body before removing all the quarter panels, etc. When I looked at the article all I saw was braces on each door. When I did my ‘65 Dart trunk floor, wheel houses and rear half of the driver’s side sub frame I did a lot more. Besides door braces, I made a cross-brace that went between each rear door jam and triangulated to the driveshaft hump (!’d already replaced the floor pans). Then I made braces our of 2” x 2” x 1/8” wall square tubing with adaptor plates that let them bolt into the shackle mounts. After the floor was out, I made a cross-piece out the same square tubing that ran across the top of the frame rails. Since I knew I was going to replace the whole rear trunk surround I made cross braces that tied it together front to back and side to side. Then I made a piece that ran from the rear pan up to the drivers side wheel house, where it wasn’t going to be cut out. Before I did all this I checked every think out with a digital level across the package tray and along the inner rail along the windows and along my welded in cross piece over the sub-frame rails. I took pictures of the readings and compared them when it was all back in, and it was the same. The only thing that was different from the factory dimension diagram was the distance between the spring perch mounts on the passenger side. It was 3/16” short from the factory. Now I’m wondering if all that was necessary. I’m just a home restorer and not a body man, although I did work in a body shop many years ago, but only doing mechanical repairs on rebuilt totals.
     
  2. abdywgn

    abdywgn dismantler

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    better safe than sorry. their way of doing it sounds "production". yours sounds "craftsman". I'd rather have you way. Bob
     
  3. Cuda416

    Cuda416 FABO Gold Member FABO Gold Member

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    If what you did worked, and you feel good about thr work, it was the "right" way to do it.
     
  4. azaustin

    azaustin FABO Gold Member FABO Gold Member

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    I have read you need to be careful when disturbing the integrity of a unibody, so it was probably overkill, but it seems to be staying put. I still have to install the replacement quarter panels on each side, but I’m hoping they won’t be a problem.
     
  5. Cuda416

    Cuda416 FABO Gold Member FABO Gold Member

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    That's very true. A unibody can "spring" out of shape when it's cut apart. best to take it section at a time if possible.
     
  6. BillGrissom

    BillGrissom Well-Known Member

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    Yes, it can be tricky to structurally secure the body. I designed thrust stands for rocket engine tests. To support a rigid body in space requires 6 independent supports to resist 3 force directions and 3 moments. Ex. to secure the top seat of a 3-legged stool with (thin) legs bolted down (resists vertical motion and 2 tilting moments off horizontal) also needs 1 side support (resists 1 horizontal motion), and 2 side supports in other direction (resists 1 horizontal motion and a twist about the vertical). When a designer misses a support, whether building a thrust stand or bridge, things can move that shouldn't. People often miss supports needed to resist a twisting moment.

    That said, an early This Old House episode had them spend a lot of time supporting a roof before knocking out a load-bearing outer wall. After they did, they found the roof held up fine without the temporary supports, which is typical in a house with all the roof framing. People here have posted photos of convertibles which sat with the frame on the ground so the frame was totally rusted away, yet the body still somehow held its shape and the doors closed without binding. Perhaps the thick steel beams in the kick panels (convertibles only) were still solid.
     
  7. azaustin

    azaustin FABO Gold Member FABO Gold Member

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    I guess I’m going to find out when I get it all back together! My goal was to triangulate all the load paths I could see or think of. The factory frame chart has been a big help in measuring before/after, and so far, so good. Thanks to everyone for their input. FABO is a huge reservoir of user-friendly knowledge, and I do appreciate it.
     
  8. barbee6043

    barbee6043 barbee 6043 FABO Gold Member

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    I set them level and cut and weld, never had any problems. Guess I am lucky. But never done a vert.

    Better to be lucky than good any day!???? lol
     
    • Agree Agree x 1
    • azaustin

      azaustin FABO Gold Member FABO Gold Member

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      That’s why I rely on luck.
       
    • 70chall440

      70chall440 Mopar or No Car...

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      Depends on what you are taking out. I have done a number of E body trunk floors and have never braced anything. I also visited a resto shop and they cut away far more than I did without any bracing. All that said, do what you think you need to.
       
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