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1934 Pontiac Convertible Coupe odd twist


Ed Davidson
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So far I can't figure out why the cowl on this car is so out of line with the body.  The bottom of the green masking tape is in the same spot on both sides.  All the measurements up from the sills are the same on both sides and the frame is level front and back.  The doors are fit with good margins.  Looking for ideas on what might be wrong, any input would be appreciated, even with a little "you dummy, don't you get it"/

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Not unusual to have cowl area and rear tub slightly off kilter during a re-fit. As a starting point, I make sure steel frame/chassis is on 4 solid jack stands (and not sitting on tires or springs for example) and is perfectly level across at base of cowl and at rear cross member where shim/bolts are (may require fine shimming of jack stands). Once this is established, ensure as you have that the vertical measurements at cowl side to side and at rear posts both side are identical. If all clear, then re-shimming of the 4 key mounting points (or 6 or 8 if necessary) will straighten out any "twist", which can be caused by many factors. Typically these cars had 1/8"-3/16" firm canvas pads (not rubber which will compress over time) and then steel U-shaped shims of 1/16" thickness were added as needed to square everything up. Mounting bolts were only snugged down, not cranked. Biggest subsequent issue after squaring is door alignment/gaps. In your car's case, it appears you need about 1/8"-3/16" extra shim at passenger side cowl mount, and another 1/8" shim at driver side rear. Then check visual alignment as per your photo. I've faced this issue on several restoration jobs, and a little patience can usually sort it out. As a further check, setting up a "batter line" from front to back also works. Clamp a vertical bar at both ends of car at centerline, pull a string tight end to end, and mark centerline of cowl and points on rear tub. Use a plumb bob to see if all major components are centered.

 

Finally, the aim is not perfection, but only satisfactory fit. Any abnormal amount of twist or mis-alignment will usually show up when doors close. When I restored my '31 Chev Coach (2 door), I probably spent 2 days tweaking the shims (4 points each side) to get doors to fit properly. There are instructions on doing this in my owners manual.

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Here is what I just tried, and it made a difference.  Jacked up the left side in the upper corner of the rumble seat opening and drew down on the right.  This had little effect on the b posts because they are pinned.  The second picture was taken when I first got the car, note the strut in place just about where I have it jacked up now.  Don't know if the strut is factory or what.

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Brace might have been put there because people climbed in the rumble seat on that side. Instead of using the steps. Causing the body to get a twist in it. You can tack weld tabs on the outside of your trunk/rumble seat lid. That over hang by about an inch. This will allow you to place the lid on the body, and not have it drop in the trunk, and sit flush with the body. Watch your gaps on the lid when you have the brace in and out. Don't get farther along to find out you transferred the problem to a different area.

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