'69 Windshield Install, continued

[Richard K.]

I called my GM dealer and the windshield install kit and spacers are NLA. Called the PPG paint supplier about the 3M Window-Weld product which contains a round Butyl tape strip of 15' and mounting blocks (spacers?). Problem is the kit comes in three different sizes of tape thickness, 1/4", 5/16, and 3/8". PPG shop has no way of determining what's needed for a '69 Corvette, they say. The NLA GM spacers were 11/32" thick. Does anyone know what thickness of Butyl tape is needed? Does it make the most sense that the tape be thicker that the spacer; in this case, the 3/8" (=12/32) ?

I checked the 3M product website, and the Window-Weld product description contains the phrase: "It's unique feature of controlled compressability allows easy installation yet will not squeeze out or allow lite to contact pinchweld". A keyword seach on Corvette yielded nothing.

[Chuck S.]

Re: '69 Windshield Install, continued

Rich, I don't think the butyl tape is what you want for a windshield. Windo-weld is a marketing name for a wide range of glass adhesives and sealers.

In his earlier post, I believe JohnH was referring to 3M Windo-Weld Super Fast Urethane, part number 51135-08609. (John can correct me if that isn't what he meant. ) It comes in a sealed aluminum tube with a pop-top end; I have a tube here for another project, and it appears the tube fits in an ordinary caulking gun. You may also need cleaner and primer with this product...check 3M's site.

Butyl tape is typically used for side glass, and I've used that too...it's sticky as heck; you have to get it where you want it the first time, cuz you ain't going to have a second try.

[Harmon C.]

Re: '69 Windshield Install, continued

I use the 3/8 and the look when finished is closer to original than something that comes out of a tube. The chance of leaks is probably greater with the tape strip and not what glass installers use today so you will need to install the windshield yourself probably. It may be illegal to use the rope for windshields I have been told. For Corvettes used little in the rain or kept indoors and hauled around in enclosed trailors rope should be fine and is eaiser to work with as the learning curve is more forgiving.

Lyle

[Wayne K.]

Re: '69 Windshield Install, continued

Rich,

If the finished product looks no different by all means use the urethane. It is a much safer install. Ask any honest glass installer. They haven't used butyl tape for years.

Wayne

[John H.]

Re: '69 Windshield Install, continued

Correct - GM NEVER used butyl tape on windshields - doesn't meet MVSS 208 glass retention requirements. Corvettes used Thiokol pumpable adhesive starting in 1968, and later changed to urethane adhesive.

[Harmon C.]

Re: '69 Windshield Install, continued

John

All original seals in 72-73 model years windshields have a material that looks like white cloth in the seal.If pumpable material was used what and how was the white cloth that is near the seal instaled and why is it their.

Lyle

[Terry F.]

Re: '69 Windshield Install, continued

Good question. I think original 68 was the same way. Terry

[Terry F.]

Re: '69 Windshield Install, continued

Who's windshield are you installing. Is it a repro and if so, who's did you buy and how does the lettering look, etc. Thanks, Terry

[Richard K.]

Re: '69 Windshield Install, continued

Terry,
I don't have access to the windshield right now, and it's been several years since I purchased it. But as I remember, it is a repro from Pilkington Glass. I believe they told me it was made by PPG. I had them date code it for me and I felt it was a good representation of original date code. In general, I was very satisfied with the product. I had purchased a windshield from OEM Glass, but they delivered it to me at Carlisle and it was chipped at the bottom where it would have shown. I wouldn't have seen the flaw if I hadn't asked them to take it out of the box. I chose not to do business with them after that.
I'm not sure how tough the judges are with replacement glass. Maybe someone else will chime in on that subject.
Rich

[Terry F.]

Re: '69 Windshield Install, continued

I don't know about the judging aspect either. But, I believe it would depend on what level of judging you are at. I believe the higher up you go (local chaptert vs. National?) you will get more knowledgeable people. If they don't spot the windshield they may spot the installation method. It is also somewhat of a give away when the glass is so nice, so they will probably look harder at it. 40 year old windshields are not that pretty usually. Take care and have fun with that car, Terry

[Chuck S.]

Re: '69 Windshield Install, continued

Lyle, the windshield installation is shown in the AIM. For the 70 AIM, the drawing is UPC 1, page F9...this location may vary slightly for other years. The windhield installation shows a "seal" (134 inches), which is also shown incidentally in the side reveal molding illustrations (UPC 1, page F4 convertible, page F10 coupe), and is referred to as "sealing strip" in the convertible drawing.

This part appears to be round cross-section material, and just as a dam is sometimes used with modern pumpable urethane adhesives, it may act as dam to keep the adhesive sealer from squashing out to the inside of the car. The "joint" in the "seal" was apparently cemented together (Item 71a, 0.28 OZ) at the center of the lower windshied frame...this would be under the glass "tongue" of the windshield that extends lower.

It may be this "seal" that supplies the cloth to the joint. My windshield had already been replaced using modern adhesive, so I didn't have the chance to examine this detail on my car. Once the adhesive-sealer and "seal" bond together, it make be difficult to determine that they were ever separate pieces in the joint.

The "seal" carries no part number leading me to believe it was a bulk-supplied commodity just like the adhesive-sealers. Other materials for the windshield installation are Item 76a, "Primer, 1.28 OZ", and Item 78b, "Sealer, 16 OZ". Optionally, Item 77a sealer could also be used. It must have been strong stuff...sixteen ounces is not a lot to glue in a windshield.

As far as judging goes, I highly doubt that the average judge is familiar with the details of windshield installation during the period, but I welcome correction. In other words, unless it's a really sloppy installation tipping off the glass replacement (there could be other clues as well), I would be very surprised if anyone could tell that urethane was used instead of the original "Thiokol" adhesive.

[Alan S.]

Re: '69 Windshield Install, continued

Rich,
I searched for a proper appearing damming strip for my 1 owner 71. I have most of the original so I knew what its typical configuration should be. I looked for about 5 years with no luck, few people had any idea what I was talking about. I ended up making a so-so strip myself. Its only 'close' but at least you can't see the sealing strip from the exterior. That was my main goal.
Alan

t

[John H.]

Re: '69 Windshield Install, continued

That "seal" (Chevrolet nomenclature) is actually a "dam" (Fisher Body nomenclature), and was furnished in bulk on a roll; the fabric served to maintain its dimensional integrity. The "dam" was adhesively applied to the glass first, cut and butt-jointed, followed by the Thiokol (or urethane in later years), and the "dam" kept the "squeeze-out" of the glass adhesive from oozing inboard past the edge of the inside garnish moldings so it wasn't visible from inside the car. Still used today.

[Patrick H.]

Re: '69 Windshield Install, continued

Where can you get some?

[Chuck S.]

Re: '69 Windshield Install, continued

John, since cement was used to join the ends at the bottom of the windshield, does that mean that this round cross-section seal/dam was a cloth covered rubber rope of some sort? Is the cloth covering of the dam visible, either from the outside or the car interior, once all the exterior and interior reveal moldings are installed?

I guess we're giving post-graduate education to some of our C3 judges...now they will definitely be looking for the cloth covered dam.