[matattack68]

I'm getting ready to install my front and rear windows on my 68. I wanted to check to see if you guys perfer to use the tape or the glue. I heard by using the tape, it makes the spacing correct for the moldings...What do you guys perfer...

Matt

[alss]

I like the tape

[Raven1]

GM never used butyl tape. And my glass guy can set glass at the perfect height everytime with urethane. We have been using the same shop for decades. Perfect bead, straight primer line and no mess.

GM never used any kind of butyl tape on any windshield or backlite; it wouldn't meet the MVSS requirements for glass retention, and didn't contribute anything to body torsional stiffness. Butyl tape is used as a short-cut installation method by some less-than-ethical glass shops, but it's nowhere near as good as urethane.

GM used Thiokol pumpable adhesive for windshields and backlites, including all 1st-Gen Camaros, which met the MVSS requirements and contributed substantially to improved body torsional and bending stiffness; Thiokol adhesive was replaced in the early 70's by pumpable urethane, the same adhesive that's still used today.

[BlueSS454]

Originally Posted by alss

I like the tape

x2 When I install glass, I put down a coat of pinchweld primer (comes in a little can with a brush to promote adhesion. After that, lay a very thin film of window weld urethane to fill in the little nooks and crannies in the surface. Then adhere the tape to the glass starting in the middle of the bottom of the piece and follow around leaving the tape hang off the edge just a tad. Make sure the blocks are in place for the rear glass, or the adjusters are set for the windshield, then lay the glass in and press it down.

[Mike72ss]

I use a combination of both. Set the glass on the butyl, then finish with a urethane bead against the tape and glass.

Mike

[Dot]

Butyl tape. Manufacturers back in the day used to use liquid butyl not urethane.

[Raven1]

Quoting John Hinckley, CRG

"GM never used butyl tape or anything like it to install windshields or backlites. Period.

The body opening flange was coated with black silane primer using a flow-brush 30 minutes prior to installing the glass, and all the reveal molding clips were installed to the Body Shop-installed weld studs.

The glass was placed on a powered rotating fixture, inside edge up, retained by suction cups.

The glass periphery was cleaned using a solvent, dried, and a different silane primer was applied.

A fabric-reinforced self-adhesive foam rubber "dam" was extruded and applied to the glass just inboard of where the Thiokol adhesive would later be applied; the purpose of the "dam" was to contain any Thiokol "squeeze-out" so it wouldn't show from the inside past the edges of the interior garnish moldings after the glass was installed to the body.

After dam application, pumpable Thiokol adhesive (with a pyramid-shaped cross-section created by the dispensing tip) was applied adjacent to the dam, all the way around the glass.

Lower glass supports were fixture-located and screwed to the cowl, and rubber spacer blocks were glued to the opening flange. The spacer blocks set the height of the glass relative to the body to ensure a good fit of the reveal moldings.

The prepared windshield was removed from the rotating fixture, installed in the body opening, and pressed down against the rubber spacer blocks; wooden tonque depressors were used to "paddle" the Thiokol around the edges at a 45* angle from the top edge of the glass to the bottom edge of the body opening to ensure a continuous seal all the way around the glass.

Reveal moldings were installed.

That was the plant production process, and explains what is sometimes described as a "rope" being found when an original windshield is removed - the "rope" is the fabric-reinforced rubber "dam" that was applied prior to applying the Thiokol adhesive.

If you'll look in Section 4 ("Fixed Glass") in the Fisher Body Service Manual, you'll see exactly the same process for windshield replacement, except the "dam" wasn't included with the Service kit - masking tape was used instead to control "squeeze-out".

The Thiokol installation passed the Federal MVSS windshield retention tests, and contributed substantially to the body's torsional stiffness; it also helped the structure pass the roof crush test. It's illegal to replace a windshield with butyl tape, although some glass shops do it as a less-expensive short-cut method instead of doing the job right."

[Motorvation]

OK, on my soap box......Your W/S and B/G need to be set in on urethane. It's a safety thing to be conform to the FMVSS, Federal Motor Vehicle Safety Standards. That's the way the car was produced, that's the way to re-install it.
Quality urethanes from OEM manufacturers like Sika and Dow Chemical have enough body to deck your W/S high enough to not be a problem with mouldings.
IMHO, test fit your clips and mouldings before the glass goes in. Test fit the glass for location in the pinchweld, blocked up from the bottom and centered. Use the primers and/or activators from the urethane manufacturer.

Steve O.

[crazy canuck]

One more vote for urethane,and Raven 1 is absolutely right!!!!Heaven forbid if you are in a head on collision the windshield will come flying out like a weapon and take someones head off.I have been in the collision industry for close to 25 years and I have seen what happens to a widshield that is butyl taped in.

[jestico]

How about this stuff from 3M:
http://solutions.3m.com/wps/portal/3...glR10HSM15F4bl

Looks like a roll of butyl tape, but they want you to 'backfill' with urethane glue after your get the windshield in place on the butyl tape.
Check out the instructions in the data sheet:
http://multimedia.3m.com/mws/mediawe...6EVs6E666666--

[Lionel-n-Chevelles]

I used urethane on my windshield. It is a superior product that gets the job done right.

[matattack68]

Thanks for al the advise guys....

[von]

I like 3M butyl tape myself. I've seen too many botched and sloppy urethane jobs, also ones where the moldings wouldn't go on afterwards.

[Raven1]

Originally Posted by von

I like 3M butyl tape myself. I've seen too many botched and sloppy urethane jobs, also ones where the moldings wouldn't go on afterwards.

That's because the guys doing it were incompetent. As stated, I/we have been using the same glass shop for decades. The man, and there is more than one tech, paints the primer on the glass then wipes it to achieve straight border that is just enough tp cover the urethane bead. Then applies a staight bead in the pinchweld of perfect height with a cordless caulking gun. I/we help him drop the window in but it's not necessary. Moldings fit perfectly every time and he does not even need them to set the glass to the right height. Now that's someone who knows what they are doing. They also know the history of glass installation procedures. If your glass shop can't do an excellent job on a classic car you have the wrong place. Period.
I just had one done by a different tech from the same shop and he did as good a job as the other guy. Their work is consistent.
I've done them myself, it's not hard. If you have no finesse and lack a steady hand then pay someone who can do it. It's not cost effective for me to do my own glass for what this shop charges, and it's guaranteed.
I've seen butchered jobs too. If you do the legwork an experienced tech can be found.

[67shovel]

I like to do it myself and have been using buytl tape for forty years. The buytl costs about $10.00 a window, roll it out and set the glass in...about 5 minutes of work. The body by Fisher manual shows how to add urathane to the top and sides of the windshield to insure no leakage. You put a bead of urathane on the top and sides after you've placed the glass and then, w/ a paint stick, you create a flat smooth slope that the water will drain off of instead of hanging around in the voids on the top. I didn't think/know that GM cars of the 60's were using the W/S & B/G as structural components yet.