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68 windshield install question.

1847 Views 5 Replies 3 Participants Last post by  bhawk
Ok I have been reading until my eyes are bleeding. I will definately be using butyl. I am concerned about the thickness of the butyl and the trim fitting correctly. Most people say to use 3/8 on the windshield and 5/16 on the rear glass. Then I see that they say that you should use 5/16 on the windshield for original glass and 3/8 on new glass because they are not as thick as the original glass. I dont like to guess on anything. I saw in one post that the rear glass, original or new is the same thickness. The post also states that the rear glass should be .237 thick. So for the rear glass I can say that 5/16 butyl with a .237 thick glass is correct. Now I would like that information for the front glass. Does anyone have or know the thickness of the original glass and also for the new repop glass? Any real world experience? I would like to end up being able to make this statement. "3/8 butyl is to be used with a windshield that is ??? thick and 5/16 is to be used with ??? thick glass.
Thx Boys
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My real world experience is this.
I bought 2 windshields from Pilkington glass, one for my 70 vette, one for my 69 cutlass. I used 5\16 butyl on both and they came out real nice, the trim pieces fit well. Didn't measure them though.
One tip--after you lay out the new tape on the car window frame, buy some urethane in the caulking tube for windshield setting, and squeeze a thin bead on the outside of your butyl tape, then paddle it against the tape with say a popsicle stick or the like. This ensures a perfect seal against the metal windscreen framing. Then set your windshield against the tape and press down to finish the seal.
There will not be enough room to squeeze any caulking tube caulk against the butyl tape after you set the glass so if you want that added insurance, do it before you drop the glass in place. I got this tip from Corvetter Fever magazine which did an article on setting windscreens and this was how a pro glass company did all their classic cars.
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Concerning Pilkington, I heard that in the last couple years they were bought out by a foreign company. Both my windshields were good quality and perhaps the second one which I got a bit less than 2 years ago was when they were under ???Japanese? control. What I can say is that they ship by freight to your door, and the glass is extremely well packaged, actually wooden crated. I did not measure the original to the Pilkington but it seemed close. Another point to consider is temperature when setting the glass. I put my windshields in during winter in my shop where temp was only about 60 F. The butyl does not press down much. If you intend to set your glass in the summer sun, it would seal better but you could press it down more easily to flatten the tape. Hence, 3\8 may work in a hot sun setting situation.
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