Is butyl rope obsolete now?

[Dibbons]

Almost ready to put the windshield and backlight in after painting the 72 SSP project car. What did the factory use to seal the glass? Do I use the same thing as the factory used back then, or just some kind of urethane sealant? Thank you.

 

[Belle66]

Picked some up last Spring at an RV sales & service store. Saw it on line too, mostly associated with RVs and boats.

 

[moparmarks]

I get it at NAPA. 5/16" and 3/8".

 

[Robliepse]

does anyone know what size of Butyl tape to use on a 1972 windshield and back glass? The local auto body supply store has 3 different sizes and I need to make sure I get this right.

 

[Dibbons]

Almost ready to put the windshield and backlight in after painting the 72 SSP project car. What did the factory use to seal the glass? Do I use the same thing as the factory used back then, or just some kind of urethane sealant? Thank you.

Update: Glass shop wanted to use urethane so that is how both my windshield and backlight were installed.

 

[Robliepse]

We're going to use the butyl so I'll buy all 3 sizes and return what I don't open.

 

[rrTor-Red]

I think 5/16" on front and 3/8" out back. Keep posted

 

[72RoadrunnerGTX]

3/8" front. 5/16" rear, with pinchweld primmer specific to butyl. I back fill with 60 minute cure urethane sealer.
Most glass shops today don’t know anything about Butyl tape and have policies against using anything but only modern urethane on anything. Problem with that on these older cars is that the glass tends to settle too deep in the opening, causing gaps with how the moldings fit. And because the sealer can be seen, it difficult to achieve a uniform application, have seen many sloppy sealer aplications.

 

[mopar 3 B]

When using urethane sealers depth spacers can be added to position the glass at the right level. I believe spacers are even shown in the 68 body manual.

 

[rrTor-Red]

3/8" front. 5/16" rear, with pinchweld primmer specific to butyl. I back fill with 60 minute cure urethane sealer.
Most glass shops today don’t know anything about Butyl tape and have policies against using anything but only modern urethane on anything. Problem with that on these older cars is that the glass tends to settle too deep in the opening, causing gaps with how the moldings fit. And because the sealer can be seen, it difficult to achieve a uniform application, have seen many sloppy sealer aplications.

I got my sizes mixed up. Thanks 72 RRGTX

 

[Robliepse]

Thanks, the butyl comes with the spacers so I should be good to go

 

[Robliepse]

I got my sizes mixed up. Thanks 72 RRGTX

Is 5/16 front or back?

 

[72RoadrunnerGTX]

The bumpers packaged with butyl tape are intended to install at the bottom of the glass to support the glass vertically, not to set the depth.

Wouldn’t have been any references to depth spacers for urethane glass adhesives in a FSM for any of these cars.

Again, 3/8” round butyl was used for the front glass and 5/16” round butyl was used on the rear glass originally.

 

[Robliepse]

All glass has been installed, I can park it outside under the tree now.

 

[Magnes]

Sorry for dragging up an older post, haven't been on for a while... This needs to be said.

Any of you guys installing your windshield with butyl tape are (God forbid) going to be in for a nasty surprise if you get in a serious accident. That stuff doesn't hold up and there is a reason why it isn't used anymore. Have a bad wreck and the last thing you want is a large piece of laminated glass flying around.

Have your windshields installed by professionals using urethane. That is it. Don't do anything else. A good glazier can run a damn near perfect bead of urethane that will look good and you don't have to smash the glass down into it so far that the trim doesn't fit well. It's easy to work with and, again, any good glazier can set it at the right height so your trim fits correctly.

I did auto glass for years. Cars would come in with that butyl tape crap and I could quite literally reach inside with my bare hand and push the entire windshield out - no tools required. That stuff has also, generally, been sitting on the shelf for years and it never seals worth a crap so you end up with leaks.

Urethane on the other hand has to be cut loose with a longknife razor. That's the only way your windshield will come loose. You could beat on it for hours with a hammer and chisel and you are NOT getting that windshield out except in pieces... So in an accident, you are protected. That is why they use it on modern cars, because it's the best way.

All the cars I've built have had new windshields done with urethane and they look perfect. It's too easy to do it the right way. You and your passengers deserve it.

 

[72RoadrunnerGTX]

Some good points, but need to counter some others. Fact is these cars were built with the fixed glass NOT designed as component of the vehicle’s structural integrity, they were designed for/around the use of butyl tape. The full structural integrity of most modern unibodies are designed factoring in the fixed glass and the adhesion of the urethane sealer as a major component. As well, most air bag designs depend on the glass remaining in place to be effective. Any flaws in a urethane glass installation will compromise the overall modern structural integrity. Most modern auto manufactures require a manufacture’s certification for glass installers performing any dealer glass work for this reason. I agree new butyl may not last as long as urethane, have seen many original 40-year-old butyl windshield installs close to basically held in place by the trim myself. Guess we’ll have to see how long urethane holds up 40+ years down the road. Disagree that the butyl sold today generally has been sitting on a shelf for years, not my experience, always been fresh when I’ve purchased it. When installed correctly, with the correct primers, as designed, there will not be leaks.

Know the Auto glass business as well, mainly as through interactions with the dealers I’ve worked with locally over the years, there are some very good installers with plenty of urethane experience and plenty of not so experienced installers too. As I mentioned, most all have zero experience with butyl. Have seen many messy old car urethane installs, with crappy fitting trim being passed off as acceptable. I’ll continue using butyl, back filling with some urethane on my 45-year-old cars, perfectly comfortable with it. On my cars that are designed for urethane, I’ll use urethane, correction, I’ll have my experienced glass shop friends use urethane when I pay them to replace the modern car glass.

 

[rrTor-Red]

If it was discussed or mentioned, I didn't see it. What kind of primer to put on the glass when using butyl?

Also, what was the sole purpose of using primer?

Thanks

 

[72RoadrunnerGTX]

 

[Magnes]

If using butyl is the correct method, why are you back filling with urethane?

And modern shops and techs are not familiar with butyl tape in auto glass installs simply because their certification REQUIRES them to use polyurethane sealant for any vehicle that will be on the highways. This INCLUDES any vehicle that originally was manufactured using butyl tape. Why? Because it's safer. Because urethane is much better in an accident. How much better? It has 10 times the strength of good butyl tape... Butyl taking about 60 psi and urethane 600 psi.

Really, I'm not going to argue it. It's like saying you can use Crisco as motor oil. Yeah, I guess you CAN use Crisco but I wouldn't advise it. If you want to take a chance with having a 5 foot by 2 foot sheet of glass flying around in an accident, and you don't mind that 3/4 people ejected from a car during an accident die, by all means... Use butyl.

I was in a head on collision in a 72 B-body. It hurts, I was lucky and I've still got the scars from over 20 years ago. We need all the help we can get and seriously, I was just trying to help.

 

[72RoadrunnerGTX]

I’m not promoting any “correct” method, simply providing correct current information about the original factory designed/dealer servicing methods from the time, as questioned by the op. Not questioning the superior adhesive properties of urethane and the role it plays in advancing today’s modern vehicle safety designs. A lot of old cars running around with a rubber gaskets holding the glass in place too, a fresh correct butyl install will do better than a rubber gasket in that regard. Also, not questioning the urethane only policy today’s glass shops operate under, 99.9% of the vehicles they work on now are/were designed to use urethane.

Back fill? Best of both worlds, the correct fit and appearance of an originally designed installation with some added sealing/adhesive & longevity properties urethane can provide.