Does any one know what diameter sealer for the rear window on a 79 would be correct? The choices at the part store is 3/8 and 5/16.

 

You do not use the butyl tape. It is urethaned in....so-to-speak...and using the blocks to hold it in place while it sets up.

If you choose to use a butyl tape ...you have to prime the pinch weld with the primer made just for butyl tape...or the tape will not stick. The butyl primer is not easily obtained due to it is "old-school" way of doing it and most glass companies do not use it any longer due to about all cars today use urethane ...which is used due the glass is also being considered a part of the structure when it is crash tested.

I know your car is old and does not fall under current standards...but butyl tape was still not used in this area for your year model.

If you look at an Assembly Manual...you will see that the product used is NOT butyl tape. But use what you want. Running fast with the tops out and the windows down in the car...do not be surprised if the rear glass doesn't come out and fly away. The only reason I am stating it is that I have seen the butyl tape let loose...even though all procedures were followed....and the butyl tape came off the glass and NOT the body.

DUB

 

So what makes the gap between the glass and the body. The blocks were not on there holding the glass up they were just there before keeping the glass centered.

 

The urethane does...just like a windshield...no different. The blocks hold the glass up so it does not collapse in too much and squeeze out all of the urethane.

The 2 blocks in the front bottom corners and also the 2 blocks in the back. The 2 blocks in the front hold up the glass...and the rear 2 blocks keep the glass from sliding down.

For what it is worth:. If you have not done so...you better take a really good look at your molding clips. And buy then from GM Vintage parts and replace them if questionable. Because when you put the glass in...you can not service these clips later.

This is a tedious job. I have done several over the years.

DUB

 

Dub, thank you for helping me out with this. So is this the correct urethane product. Also how much do you think I need? Do you recommend placing the window in before or after paint. When I took it all apart there was only 3 blocks, one in the back was missing, where can I get these. I am replacing all of the clips that hold the trim on.

 

Yes...you can use the 3M 8609. BUT FIRST...you will want to call and talk to 3M tech dept. The reason being that it requires special cleaners/primers for the glass and the body. Also the work time may be too fast...and you may take a look at the one that is slower.

Also from the classes I have been in...the surface of the pinch weld...where you are going to apply this urethane needs to be primed and that is it. NO PAINT AND CLEAR.

The reason has to do with SHEAR. The automotive manufactures often use the glass as a part of structure during crash testing...and in doing so....they do not want the paint and/or clear to shear off of the primer....or even excessive film build of a primer shearing off....thus allowing the glass to fly out. SO it is best if you only apply a primer and leave it and then apply the primer so the urethane will adhere as designed.

I know your car does not really fall under the procedures of today's cars being made...but I always err on the side of caution and implement procedures that are more current ...even though your car was not built that way. It is always a liability thing with me.

NOW...you can paint and clear the surface that your new windshield molding clips will lay against. That is fine because no urethane is going to be applied there.

it has been some time since I have had to install a back glass like yours...but I honestly can tell you that I still would call 3M and talk with them to verify that the procedure is still the same...or if new products are out on the market that could even allow me not to have to apply any spray-on primer on the surface where the urethane will be applied...and I only have to brush on their product for maximum adhesion.

If you only go and use the 3M 8609...do not be surprised if you have a problem...so ...really take the time and call and talk with someone at 3M.

DUB

 

I agree to not use it. After a month after I put mine in using the tape I got from the auto store the glass fell out. I'm going to let the glass guys put it in when they put the windshield in.

 

I am not knocking the glass guys you have chosen to do this. But I can tell you that I hope you are there when they do it...and you CLEARLY tell them your expectations.

I am so picky when the windshields are being installed. I take some serious time in setting up rubber stops to make sure that when I set the windshield in place ...and the moldings are all installed and checked...that the upper molding all the way to the corners is RIGHT. I hate nothing more than a windshield that has a gap between it and the moldings that you can slide a cigar in between them...ESPECIALLY at the upper outer corner areas.

DUB

 

I have watched him do it. He first puts the chrome trim on, then takes a piece of glass that is the same thickness and sets it in in 4 places. He then takes the spacers and finds the right thickness that put the chrome setting on the glass correctly. After removing the chrome he sets glass on the rubber spacers the measures it setting up these strange devices so when the glass edges are where he wants it. He then re measures it once glass is sent on vehicle. When I saw him do it the measurements were correct. He owns a bunch of Street rods/Muscle Cars and shows them out here all the time.

 

You definitely have a competent guy installing the glass...that is for sure...and I an glad to read that there are people who do it correctly instead of just slapping it in and letting it ride. Take the time to DO IT RIGHT is what I always say.

DUB