1970 GTX quarter panel crack

Exterior Body, Paint, Trim, Chrome

  1. Fm3 Dart

    Fm3 Dart Well-Known Member

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    No, it is not from body twist.
    It is from the lead separating from the metal. This is joint where the windshield pillar is welded to the cowl. The factory did some gobby welds, then covered up the mess with lead. Which would have lasted had they actually neutralized the acid used to tin before leading the seam.
    You will see this same issue at the rocker to quarter joint and the roof pillar joint on painted roof cars (vinyl top cars got bondo, yes bondo, from the factory).
    I can assure you that body twist is almost a non issue in a 68-70 Mopar B body. You want to see body twist, look at the GM full frame cars. unibody cars are so much more rigid than any body on frame design.
    The crack by the door also has zero to do with body twist. It is from the stress of the door being slammed a thousand times, and road vibration adding to the cracking.
     
  2. beanhead

    beanhead FBBO Gold Member FBBO Gold Member

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    Wow ok...that's the first time I've heard that. I thought that's why when adding power we like to tie the subframes, add torque boxes etc(like the factory did on higher HP cars?)...I agree with you on the quarter cracks that's why I stated my 318-equipped car had them on BOTH sides
     
  3. Fm3 Dart

    Fm3 Dart Well-Known Member

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    Yes, adding torque boxes etc is definitely a good idea, and does add strength, no question.
    But Chrysler was also pro-active with Hemi cars and other high performance models. Adding torque boxes and reinforcements to Hemi and Six Pack cars and 340 A bodies, and convertibles was a preventative measure more than necessity. Kind of like putting Dana 60's in 440 and Hemi 4 speed cars. A bit overkill, but it made warranty issues from hard driving hooligans almost non existent.
    And Hemi hardtops got the door jamb cracks too...
     
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    • Photon440

      Photon440 Well-Known Member

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      Not quite. It's true that a plastic filler was used other than lead, but it wasn't bondo. It was Plastisol, which is a polymer that doesn't use an additional hardener to cure, instead it hardens with heat once it reaches 177c. becoming waterproof but still slightly flexible. After it was smoothed onto the seam, the oven baking process for the paint hardens the filler.

      This is why it's easier to replicate leaded seams on a car, most people don't have either the material or means to properly bake the product.
       
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      • Fm3 Dart

        Fm3 Dart Well-Known Member

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        Good point. I should have said plastic filler, rather than bondo.
        Bondo is a brand name that I shouldn't use generically anyway.
         
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