# What goop was used in body seams?



## pkandersen (Feb 12, 2021)

They used it under here and under there, they used it everywhere. What is it and where can you get it? I'm restoring a '65 hardtop and it is bare. Inside gutted and quarter panels and trunk pan removed. Don't know what to use. After 56 years the stuff is getting brittle and breaking off. Thanks for your help. Pkent


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## Jetzster (Jan 18, 2020)

Roger1 on his thread with his restoration expertise can prob answer your question
If he can’t, nobody can😀









My '69 GTO Convertible Body-off Restoration Thread


I have to say your work is impressive, the attention to detail shows true love of your craft. Keep up the good work! Thanks! I appreciate your comment. And yes, working on cars has been a hobby for me since I was a teenager and am fortunate to be able to make it my focus in retirement.




www.gtoforum.com


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## GTOTIGR (May 3, 2020)

Hi pkandersen,

There are several manufacturers of auto seam sealer, I’ve provided three. I personally used the gray colored sealer when I did my 65. 






Amazon.com: 3M Dynatron Auto Seam Sealer Caulk, 550, Grey, 12 oz: Garden & Outdoor


Buy 3M Dynatron Auto Seam Sealer Caulk, 550, Grey, 12 oz: Sealers - Amazon.com ✓ FREE DELIVERY possible on eligible purchases



www.amazon.com










Amazon.com: ACDelco 10-2013 Body Joint and Seam Filler Compound - 11 oz: Automotive


Buy ACDelco 10-2013 Body Joint and Seam Filler Compound - 11 oz: Sealants - Amazon.com ✓ FREE DELIVERY possible on eligible purchases



www.amazon.com













Amazon.com: SEM 29392 Black Seam Sealer - 10.1 fl. oz. : Automotive


Buy SEM 29392 Black Seam Sealer - 10.1 fl. oz.: Sealants - Amazon.com ✓ FREE DELIVERY possible on eligible purchases



www.amazon.com


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## pkandersen (Feb 12, 2021)

That was most helpful. I've asked paint shops and body shops and I don't think many use it. Do you use a body putty knive to spread it flat? pk


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## GTOTIGR (May 3, 2020)

Hi,

I used the ol’ finger spreader after applying with a caulking gun.


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## O52 (Jan 27, 2019)

No need to be neat about it, the factory sure wasn't.


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## pkandersen (Feb 12, 2021)

GTOTIGR said:


> Hi,
> 
> I used the ol’ finger spreader after applying with a caulking gun.


Like I said they used it everywhere and you are right it wasn't a precision job. Thanks for your input. I might wear a latex glove so my hands stay pretty. pk


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## GTOTIGR (May 3, 2020)

That’s smart, but recognize that the seam sealer will want to stick to the glove - think caulking your bathtub/sink/shower...

I kept water close so I could keep my finger wet so it spread smooth. Not pretty necessarily but smooth so when you paint over it it’s clean versus bumpy with ridges.


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## 64since65 (Dec 11, 2019)

Spread it smooth? Based on what I've seen on the two cars I recently gutted, that won't look very original. It looked to me like they pretty much put it on with a big caulking gun and only flattened it as much as necessary. I can't find any photos of the body seams but this before/after shot of the vent housing by the kick panel shows how much they gooped it on there.

I have no idea what the official name was for this stuff but when I worked on the line at GMC Truck & Coach in the late 60's we called it Dum-dum. (One of my jobs as a co-op student was finding out where all the heat was going in the winter thus making it hard to keep the cabs warm on the cab-overs. The very high tech solution was to fill the 3-4 largest holes with dum-dum. Of course, that was after destroying one cab by blowing talcum powder through it to find _all _the leaks when we could have just felt where the air was blowing out and sent the cab back to the production line! Hey, I did what they told me to do.)

Not saying you shouldn't smooth it out to make it look better. Just commenting about how they didn't seem to worry much about that in production. I'm sure it was more about speed than appearance. And, yeah, it's getting a little bit brittle but I was also surprised at how flexible it still is.


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## GTOTIGR (May 3, 2020)

Hi 64since65,

I believe that the body seam sealer material that was applied to the seams was a different material than what was used to seal things like the interior vents you reference. The caulking material for things like vent housings were applied as you say and then pressed together. The vent material remained softer and more pliable than the body seam sealer that was painted over? Of course both over time became harder and brittle.

Here are a few pictures of trunk lid seams sealed for reference.


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## 64since65 (Dec 11, 2019)

GTOTIGR said:


> Hi 64since65,
> 
> I believe that the body seam sealer material that was applied to the seams was a different material than what was used to seal things like the interior vents you reference. The caulking material for things like vent housings were applied as you say and then pressed together. The vent material remained softer and more pliable than the body seam sealer that was painted over? Of course both over time became harder and brittle.


Ah yes. Thanks for the enlightenment. I wasn't thinking about those areas. Those vents are by far the worst when it comes to putting it on thick. I was thinking of some other seams around the cowling under the fenders, in the trunk, and under the carpet that weren't nearly so neat as the ones in your photos - presumably because they aren't as visible even though they are painted. I went out and took a closer look and you're right - most of that stuff is a different, harder material. I knew the stuff on the floor around the seat brackets was definitely different - more like some kind of hard tar - but hadn't really paid attention to the material on the other seams since that wasn't really a factor in gutting the car.


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## GTOTIGR (May 3, 2020)

Looking at “roger1” 69 restoration further emphasized that there are many types of sealer material used on the GTO’s. The floor to rocker seam also used another type of sealer. As did the floor pan drain plugs...








Looks like the question/ topic is broad and has an array of options.

Ames Performance

These colored seam sealers can be brushed after application for original appearance. Seam sealer cannot ship via air or outside the Continental United States.
J207 
Seam Sealer, Tan (AP) ............................... 
J207B
Seam Sealer, Black (AP)............................
DRAIN PLUGS & SEALER
K157N 1967-77 Steel Trunk Floor Drain Plug, A-Body (RE) 4.50/ea.
Thisisthesteeldrainplugfoundintrunkfloors. K157Nisheldinplace with seam sealer

18.00/tube 18.00/tube
K157NC 
Seam Sealer, Tan (AP) ............................... 
K157ND
Seam Sealer, Black (AP)............................

Cheers


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