Do promos ever stop warping?

[hedotwo]

I have a perfectly straight 57 promo buick that had a metal friction chassis, nice glass, and no interior.  I disassembled it totally and now wonder if after all my upcoming work to build an updated look with new paint, chassis and interior, will it begin warping do you think?  Or if it was going to warp would it have done it after 68 years?  Anyone have experience doing something similar?

[Bugatti Fan]

After all this time the plastic probably will not warp, but it might have become a bit brittle.

[hedotwo]

1 hour ago, Bugatti Fan said:

After all this time the plastic probably will not warp, but it might have become a bit brittle.

What I was thinking (and hoping) too....  

[Ace-Garageguy]

I have an acetate early '50s Pontiac promo that was badly warped when I bought it, it continued to warp, then started breaking into chunks, and the body now is literally dust.

I also have two late '50s Oldsmobile promos that I assumed would be acetate, but they have not warped or shrunk at all.

I can only surmise the non-warped ones are made from something other than acetate, which as far as I'm aware, will continue to deteriorate forever.

[Mark]

3 hours ago, Ace-Garageguy said:

 

I also have two late '50s Oldsmobile promos that I assumed would be acetate, but they have not warped or shrunk at all.

 

What year(s)?  The original Jo-Han promos were all acetate through the 1963 model year.  They did reproduce '56, '57, and '58 promos through their X-EL division in the Seventies and Eighties.  Those are molded in ABS which does not warp and has a nice shine also.

[espo]

On 9/10/2025 at 2:07 PM, hedotwo said:

I have a perfectly straight 57 promo buick that had a metal friction chassis, nice glass, and no interior.  I disassembled it totally and now wonder if after all my upcoming work to build an updated look with new paint, chassis and interior, will it begin warping do you think?  Or if it was going to warp would it have done it after 68 years?  Anyone have experience doing something similar?

Maybe consider using the Promo body to make a mold of it while it is still in the correct shape. 

[hedotwo]

2 minutes ago, espo said:

Maybe consider using the Promo body to make a mold of it while it is still in the correct shape. 

That's an option I guess.

[Ace-Garageguy]

7 hours ago, Mark said:

What year(s)?  The original Jo-Han promos were all acetate through the 1963 model year.  They did reproduce '56, '57, and '58 promos through their X-EL division in the Seventies and Eighties.  Those are molded in ABS which does not warp and has a nice shine also.

One's a '58, of that much I'm certain. I'm 98% sure the other one's '57.

They both look for all the world like a factory promo, with excellent (but obviously not sanded or buffed) two-tone paint jobs and the same perfectly-masked silver paint treatment of body chrome as I've seen on other promos that were most definitely acetate.

Neither one looks at all like it was done by a modeler, unless he was VERY good at replicating factory promo finishes.

[Mark]

If the chassis is attached with metal rivets (screws without slots in the head, for lack of a better description) they are original promos.  If the "rivets" are silver plastic pins, they're X-EL repops which are probably worth more than any but the best condition originals (because of the non-warping materials used).

The X-EL repro promos were very well done finish-wise.  Some of them lack interiors (in spite of X-EL's propaganda saying the originals didn’t have them either), most have the no-detail plastic chassis plate with provisions for a friction "motor" that isn't there, and at least one had some jury-rigged assembly like a taxi sign propping up the interior bucket).  But would many of us like the chance to buy another...you bet!