Hot Rods sheet metal gurus--34 pickup question

throwing this out for consideration. I'm starting to think about metalwork on my cab but this has me stumped.

as a preface the truck went through a house fire in 1975 and the body was severely damaged. the roof was already replaced with a donor circa 1990.

I recognize I'll have more money and time in it than I should but with the family history it a new cab isn't in the cards.

the cab back is warped and swoops inward presumably from fire damage. assuming it is supposed to be flat there is a 1/2 to 3/4 inch recess at the deepest point (see pics)

the question is how to straighten this back out?

I'm anticipating a new cab back and corners but that won't correct the warp in the body line that's holding it in place.

if I push it out it pops the other way and stays domed (see pic) but won't retain shape without support.

thoughts?



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I bought this book years ago and it has been invaluable. Really helped me with my shrinking using an torch. I do a little with shrinking disc, but have not mastered that yet. You need to shrink the back panel and since it was fire damaged, that makes it more difficult. Takes alot of practice. If you have smaller areas that 'tin can' I would start on those areas first.

 

that might be easier to replace

this is a howell piece. looks simple to make
this would be below the belt line
might make repairing the belt line section easier
X2 on the keys to bumping metal book, also youtube is your friend

there is stress on that panel somewhere since it is popping in and out
I had a early 40s GM that did the same thing due to having fire wood being tossed in it over the years
I fabed and replaced the rear section of the cab after a day spent trying to fix the heavily distorted panel

 

I'm quite familiar with the bumping book.

I'm afraid the warp is "locked in" by the body line and the new section will just be drawn down to match.

can't get my head around how to shrink the body lines

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some of it could be lower damage
body lines can be shrunk with a torch and hammer just like anything else, use an appropriate dolly
here I one thing that might help
if you take a block of wood and a sizeable hammer and "message" the floor down where the rear cab is welded to it may tighten it up

the damage below the belt will have to be addressed as well in order to relieve the stresses in the cab


also why was the roof replaced?

 

I think the fire already did its own heat shrinking, but not in a preferred manner. You need to realize the heat also added some temper in some spots and weakened it in others. It will be a continuous chase around that back panel until you finally get it close enough, give up, and bring on the bondo.

Just work on pushing it into a close shape first before you add any more heat or shrinking. May take friends pushing/holding the good spots with some wood blocks while you are inside pushing the dips outward with a hammer and another 2x4. Work on the general things first and watch where those oil cans are. Mark them with a pen for later.

 

Worst case scenario, you could make vertical cuts through the reveal bead in a few places with a thin cut off wheel. Either bolt the cab wood or some type of tubing in place to force it where it belongs and carefully tack weld the cuts. The problem with heat damage is its hard to identify where the distortion is coming from and shrinking or stretching the wrong areas will just make it worse.

Dave

 

Worked on a junk '34 cab last year. The holes in the back belt line hold in a wood seat spring mount. If I was you I'd fab up a U shaped piece it steel tube that connects to those mount holed and attach both ends to the B pillars, this way you have a good strong base to work form. Bob

 

1) no floor at present
2) roof replaced because it got so hot in the fire it sunk in about 6 inches and was cut out when I got it back. coincidentally the cowl similarly damaged. it basically sunk flat.


thanks for all the suggestions. I'm wondering about trimming the back panel out half and inch or so below the belt line and trying to use a shrinker on that area before replacing the back panel . trying to visualize how the metal will move in that scenario in my head.



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If the cab was in enough heat to cause the damage you described then there was certainly enough heat to damage the back of the cab. Steel shrinks when heated so the panel would need to be stretched. Replacement would be the best option.

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I plan to replace the back panel ( and the uppers as well) my issue really is with the belt line and getting it to straighten out.

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I have had a handful of those cabs and everyone has been pushed in slightly in the back... I suspect from stuff hitting the back for all those years especially on the big trucks

 

Yeah, sometimes I wonder if they were just made that way from the start.