The Stovebolt Site Forums The Parking Lot '60-'66 Trucks To fill or not to fill air gap between roofs

I have an idea which is either incredibly brilliant or incredibly stupid. I just can't decide which, and I'm hoping to save myself a huge mistake.

The area in question is the air gap between the cab roofs that extends back behind and around the back window. I have a hole drilled through the roof where a spotlight had been mounted.

The idea: After I weld a patch topside, how about squirting some real low expansion foam filler in there??

I thought this might be a good way to insulate against heat/cold/noise without adding anything to the interior of the truck.

My concern is what if it somehow traps moisture and rusts out the roofs. The only way I can think of that moisture would get in there is from condensation, but I guess it's possible.

Has anybody done anything like this? Did it work well? Any thoughts, ideas, or personal experiences would be appreciated. Like I said it's probably either brilliant or stupid, so go ahead and tell me either way.

Thanks! You guys and gals are awesome! I love stovebolters.

If you want to put something in the space between the roof panels, I'd use something inert like silicone sealant. There are just too many horror stories about spray foam. I would never dream of using it in a vehicle.

You might want to check out this thread:

http://67-72chevytrucks.com/vboard/showthread.php?t=440440

Yep, ... it was an incredibly stupid idea.
THANK YOU for posting the link. It was a good eye-opening read. Those pics of the suburban I think pretty much say it all.

I am not so sure about it being a dumb idea. It appears to be injected into refrigerators. I have seen it used in refer and freezers on ships - course those were stainless steel.

I do not underetand why it would be a rust magnet any more than any other unventilated space - assuming you leave no voids.

The big caution in my mind would be when the stuff swells. Shipyard had a big problem with this factor. Built large forms like those used in concrete. I can easily see it warping a cab if hi expansion was just willy nilly shot in and no allowance made for expansion.

Dan Bentler

Well, I won't go so far as to say it's a dumb idea for everyone. BUT, I'm not going to risk it.

I opened up my hood yesterday early yesterday morning at 34 degrees Fahrenheit and there was beads of moisture all over the underneath part of the hood. And I thought, "Self, if that is there under the hood, what is in between the roof panels?" Now, I don't know the answer to that question, but it seems like a reasonable guess that there was some moisture there as well.

Also, I'm fairly confident that I couldn't spray the stuff conservatively enough not to swell the panels, and yet enough to make sure there were no voids. I'm just NOT that good.

So, long and short, I'm steering clear of the stuff. Lots of interesting info on it, though.

Thanks!

Used the stuff in refrigeration back it the 70's Had to measure carefully and have expansion holes in lots of areas/

What about using cavity wax? Eastward sells it and I believe that is what it is designed for is areas such as this.

There certainly is a lot of info on the web about different cavity waxes and even greases. All very interesting reads.

Thanks for the idea. It would probably take care of the possible rust, but it wouldn't do anything to insulate noise and temperature.