Case of the Missing Bolts

Discussion in 'Race car chassis tech' started by Dragdoc, Dec 3, 2018.

  1. Dragdoc

    Dragdoc Well-Known Member

    OK all you Hardy Boys, got a mystery to solve. In preparing for body removal before frame mods we found no body mount bolts in front of the rear wheel wells. Actually, just ahead of the lower control arm mount. There is an upper rubber biscuit, a hole through the frame, but as far as I can tell no hole in the body. No indications there was ever a lower rubber biscuit.

    Whaaaaaaaat??? Is this normal? Is it cuz this is a small block post car not a performance GS 455? Was this the last car assembled on a Friday afternoon before a major holiday?!?!?!
  2. Brad Conley

    Brad Conley Super Moderator Staff Member

    Could be either way, but many times the engineers tuned the ride by this method.
  3. Dragdoc

    Dragdoc Well-Known Member

    So a more flexible hard top would possibly have bolted mounts there, and a stiffer sedan/post may be “softened up” by the dummy mount? Kinda makes sense.

    Hoping the polygraphite body mount kit has provisions for a “complete” mount in this questionable spot.

    Anyone out there able to confirm that this mount is typically bolted in other body styles?
  4. DasRottweiler

    DasRottweiler -BuickAddict-

    My 70 hardtop has 4 pucks. Jim
  5. Duane

    Duane Member

    I don't know what year GS you are talking about,
    but for the 70-72 Buick cars it went like this
    4 Bolts at the firewall regardless if it was a coupe or convert.
    2 Bolts under the doors
    2 Spacers before the rear axle
    2 spacer above the rear axle
    4 Bolts after the rear axle

    Now from what I was told, the Buick engineers wanted a smoother ride, so they installed spacers before the rear axle so the frame could "move" a little.

    Chevy's put the spacer under the doors and used a bolt before the rear axle, so the frame would not move.

    W30's and W31's used a bolt at all locations, so frame flex was kept to a minimum.
  6. Dragdoc

    Dragdoc Well-Known Member

    Ah, perfect.

    Thanks Duane thats just the sort of difinitive answer I was looking for. I will turn spacers into bolted mounts if possible. Hoping the body mount kit allows for this.
  7. Duane

    Duane Member

    You will probably need to buy 1 extra pair of body mounts, and toss a pair of spacers.

    Bolting every body mount position along the frame rails is an old racers trick. This would keep the frame more rigid in relation to the body. The idea was if you kept it from flexing then that power would go to the back wheels.
  8. BrianTrick

    BrianTrick Brian Trick

    I am doing this same thing right now. I ordered a half set of bushings to give me a few more,so I can bolt all of them.
  9. tsgp51

    tsgp51 Well-Known Member

    Here is the 70 assembly manual page.Just Duane said. Cheers Tim IMG_20181204_170247366.jpg
  10. Brad Conley

    Brad Conley Super Moderator Staff Member

    And you doubted YoDAH?????
  11. Duane

    Duane Member

    Tim doesn't doubt me, but he does keep me in line.:D

    Tim is da man.
  12. Dragdoc

    Dragdoc Well-Known Member

    I should expect NO bolt holes, welded nuts, etc in the sheetmetal areas with spacers, correct?

    Whats the best way to add fastening ability? Im picturing welding a nut to a fender washer put that nut side into a hole in the sheetmetal and weld washer to body. Probably the easiest instead of welding a nut directly up in a hole in the sheetmetal (easy to burn through, hard to orient the nut).

    Open to suggestions!
  13. Buicksky

    Buicksky Silver Level contributor

    There should be no bolt holes or a place to put the bolts you didn't remove. It was designed and lasted 50 years the way you found it. The spacer is not going anywhere once you tighten the rest down. I would just replace with new body mounts and move on to the next step. Why cut extra holes and re-engineer a good design ? But that's just my opinion.
  14. Duane

    Duane Member

    I think the bolt hole with the captured nut is already in the body. The way GM made it's money was by using the same pieces for multiple cars, and for the most part they did this with the floor pans as well. That way each division could bolt their parts on and there was no reason to make extra pieces.

    Pictured below are shots of my 70 442 convertible getting an entire floor pan installed from another olds. I did this years ago. The design of this floor pan would fit any 68-72 GM a-body for a 2-door car regardless if it was a coupe or convertible. This particular one was from a bucket seat car with the Hurst Dualgate, which was exactly what was in my car so I didn't have to do anything except install it.

    If you look at the floor pan brace you can see the captured nut in the pic. This is the body mount we have been talking about in this thread.

    PS. You still haven't said what year GS you have.

    Picture 001.jpg Picture 002.jpg
    Last edited: Dec 5, 2018
  15. Duane

    Duane Member

    .............and if you wanted to know how the body was held together while I was doing this then look at this pic. I welded an entire roll cage in the body before I took it off the frame. The result was that nothing moved.:D:D

    Picture 004.jpg
  16. Dragdoc

    Dragdoc Well-Known Member

    Nice cage Duane! Very mad max looking. I did the same for a couple cars I chopped the top on.

    Are you asking ME what year GS? Not a money car! Its a low buck ‘72 Skylark two door post. Black steelies and dog dish caps. Shhhhhh! Motor will have a little more grunt than the original 350 2bbl - hence the frame boxing, etc.

    Attached Files:

  17. Duane

    Duane Member

    Just wanted to make sure it was a 68-72 car, that is what my material is referencing.
  18. Dragdoc

    Dragdoc Well-Known Member

    Body is off the chassis! The floor pan has welded nuts above the spacers in front of the rear wheelwells, but not by the rear spring pockets.

    That body is surprisingly rigid - and the interior, glass, etc is still in it. The sawhorses are not on level concrete and I had to shim the points where the body rests! Round if applause for B pillars...

    Attached Files:

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