I think my weather strip’s to thick

Question:

I am restoring a 1980 Camaro with a T-top. I really enjoy your magazine because it has helped me tremendously with my restoration project. Now I hope you can help with the problem I am having with the T-top weather strip.

I have bought new weather stripping from two different manufacturers and both have fit perfectly into the T-top slots. The problem is that I cannot install the T-tops with the weather strip in place. I weigh over 200 pounds and I cannot push hard enough to get the tops to slide in place over the retainers. In my estimation the weather strip is too thick.

When I talked with the manufacturer they suggested I put the car outside and let the weather strip heat up in the sun. I tried that. I tried putting grease on the rubber, all to no avail. I even broke the thin aluminum channel running around the glass trying to install the tops. (Fortunately, there is a repair kit for that.)

I know there were two manufacturers for T-tops that year (Hurst and Fisher). I am sure I have the Fisher tops due to the single release lever. The weather strip is supposed to fit the Fisher tops. Do you have any suggestions? I am about to try trimming 1/4” off the weather strip all the way around. (Foolishly, I threw out the original weather strip so I cannot compare thicknesses.)

Answer:

I encountered this same sort of problem many times in my restoration shop. Sometimes the reproduction seal’s physical dimensions are different. Sometimes its physical properties, namely its hardness or Durometer range, are different. And, of course, it’s also possible that both are different.

A lot of times automotive weather stripping is tubular (hollow inside) and while the outer dimensions of the reproduction may be the same as the original, its wall thickness may be different. Even if the repro is manufactured from the same type of rubber, the thicker walls will increase its hardness.

The compression set of rubber is a measurement of its ability to return to its original thickness after prolonged compressive stresses at a given temperature and deflection. If your reproduction seal has relatively poor compression set performance it will get progressively easier to close the door, close the trunk, put the Ttops on, etc. Of course, this presumes that you can get the T-tops on in the first place.

When we did full restorations on certain cars where we knew we’d have a weather strip problem, we’d sometimes install the reproduction weather stripping as early as we could so as to let it begin compression deforming.

Sometimes I selectively trimmed the seals by cutting or grinding them. Sometimes I used seals sold for one application on another one because the “wrong” seals functioned better than the “right” ones.

In many cases I reused the original seals when their condition allowed it.

In your particular case, you violated one of the basic rules of automotive restoration when you threw away the old weather strip before the job was completed. At the very least you could have compared the reproduction seals to your originals to help determine what’s wrong with the repros. And perhaps you could have also had the option of reinstalling the old seals if they were still in usable condition. But, that’s water under the bridge now.

If I were in your position I’d try modifying the reproduction seals by trimming or grinding them.