First a little history on how to install a windshield:
- Rubber window channel
Originally used up until the early 60s for windshield on cars but used much longer for flat glass windows and truck
windshields. Basically it is a rubber channel that surrounds the windshield and holds it into place in the windshield frame.
The windshield fits into a groove in the rubber channel. There is another groove that the windshield frame flange fits in.
You place the windshield with the rubber channel against the windshield frame. Previously, you've
placed a soapy wet string in the frame groove. A buddy presses against the windshield from the outside, you pull the string from the inside hoping that
the string will pull the rubber groove over the frame flange.
- Run the string completely around inside the frame groove. The two end pieces should be exiting in the bottom middle.
- Use lots of soapy water - liquid dishsoap works very well.
- While someone pushes from the outside, pull both strings evenly starting from the center bottom
- Have a plastic knife or flat blade handy to help lift the rubber frame groove lip over the flange.
- Butyl Ribbon Sealer
Butyl ribbon sealer was used starting around the late 1950s. There is no rubber windshield channel, the windshield is placed flush against the
windshield frame flange with the butyl ribbon sealer on it.
The butyl ribbon sealer would provide the watertight seal required but doesn't have the holding
power that is required to hold the windshield in place. The external stainless trim's job is to hold the windshield in place.
Butyl Ribbon Sealer comes in a box like this
This is what it looks like - a black very sticky rope!
You can purchase butyl ribbon sealer in several different sizes: 5/16" and 3/8" round, 3/8"x1/4" flat, etc.. I used 3/8" round cause I don't know
any better. It worked! Note: You have only one chance to place the windshield against the butyl rubber sealer then its pretty much stuck (more on
- Urethane Adhesive
The windshield in modern cars is part of the roof structure. Previously, the windshield was allowed to float in place and wasn't structurely strong.
Urethane adhesive bonds the windshield to the windshield frame flange making the windshield part of the roof structure.
Urethane adhesive comes in a caulking style tube
The procedure is to clean the windshield frame flange of any old adhesive, if you don't have primerless adhesive, then you must put a layer of
special primer, let it dry then place a bead of urethane adhesive around the flange. Place the windshield on top and your done!
Installing the 1954 Pontiac kustom's windshield
My plan was to install the windshield the same way that Pontiac orginally planned using a rubber channel. A few difficulties arose as I had to
cut 6 inches off the stock rubber channel to compensate for the roof chop.
The first issue was finding a glue that would cement the newly cut rubber channel back together! I tried contact rubber cement, superglue, crazy glue, black silicon, a magic glue my mother bought from Germany and none would hold the ends together
reliably. Another issue was cutting the ends cleanly! A thick 1" of molded rubber channel does not like to cut cleanly. Cleanly meaning leaving a nice
flat 90 deg edge so that the two ends would mate properly.
Very difficult to cut cleanly and glue the rubber channel ends back together!
Three slots - one for the windshield, one for the frame flange and one for the stainless trim!
The last issue is that the windshield stainless surround trim has to fit into the rubber channel also. The whole assembly consisting of the windshield,
6 separate pieces of stainless trim and the rubber channel has to be held together as a unit and placed on top of the windshield frame to be installed
all together! I'm amazed that anyone could do that as putting the rubber channel on the windshield was like wrestling with a python!
Wrestling with a python!
Thankfully, I was saved trying when I test fitted broken windshield 2 and found that the roof chop wasn't done quite right and there was no way that
the windshield would fit in even if it was not broken! The top angle of the windshield frame was laid back a little bit too much - it was too rearward.
The left to right angle of the top was also increased from stock so that the windshield at the A pillars stuck out about 3/4 inch. There was
a 3/4 inch gap between the glass and the A pillar! On to the emergency backup plan!
Emergency Backup Plan!
The emergency backup plan was dead simple: cut a new windshield so it would fit the windshield frame opening, use butyl rubber sealant to
provide a weatherproof seal and glue the windshield in place with urethane adhesive for structural support. In hindsight, this was the simpler
way to go then trying to go the rubber channel method.
After making a new template based on the laying the winshield against the windshield frame and cutting windshield number 3,
we were ready to install! The winshield frame lip had to be bent in several places so that the windshield laid flat on the frame lip across
the top. The sides were still off but only by 3/8" or so. I could work with that.
1/8 inch rubber spacers placed at the bottom of the windshield so it doesn't rest directly on the windshield frame
The gap at the top of the windshield is an even 1/8 inch
Typical gap at the A pillar - about 3/8"
Small 1/8 inch rubber spacers were placed at the bottom of the windshield so it wouldn't rest directly on the frame. Later I'll fill the gap with
urethane adhesive to hold the windshield in place. The urethane adhesive will provide some cushioning and allow very little flexing.
With the windshield exactly where I wanted, I placed some strips of masking tape in each corner and cut them at the windshield-frame gap. Later when
I go to place the windshield in permanently, I won't have to move it around much.
Masking taped corners for alignment
The windshield and frame are ready to be installed!
The butyl rubber sealant was run around the windshield frame lip starting at the bottom center. I had to double up on thickness for the A pillars
to make up for the gap. With a buddy, place the windshield onto the windshield frame very lightly while using the now out of aligned masking tape guides?
The 3/8" thickness of the butyl rubber sealant will throw off the nicely taped guides. Split the difference so that both sides are off by the same
amount which was 1/16" in my case for each side. Butyl rubber sealant is supposed to be applied between 73 and 100 deg F. My garage was at the
low end of the temperature so it wasn't as sticky as it coulde be. So I drove it out in the sun!
Warming the butyl rubber sealant in the sun
Once the windshield is in place, start at the bottom center and press the windshield into the butyl rubber sealant. Press all around the windshield.
You are trying to make a 1/4 seal which will show up as a black flat spot through the windshield. I had to press the butyl rubber sealant from
the inside in several places to make sure it was thick enough at the bottom. The sides were another story as they required a constant squeezing
together from the inside and out to make up the gap.
- Wear thin latex gloves! The butyl rubber sealant and the urethane adhesive does not wash off your hands!
- Brake cleaner does a great job of cleaning butyl rubber sealant off of the windshield glass.
- Be paranoid about masking up the dash, hood and windshield surround to stop accidentally ruining your paint with the urethane adhesive.
- The urethane adhesive cleans up easiest when first applied.
Now that the windshield was in place, it was time to caulk the gap with urethane adhesive. A nice thin bead was run across the top and bottom gaps to
fill in the 1/8 inch gap. The nozzle was cut larger and the gaps between the A pillars and the windshield were filled in. It is important not to
move the car for at least 12 hours to allow the urethane adhesive to cure to full strength. If you move it earlier, the windshield/frame may flex and
the urethane adhesive will lose half of its strength!
Finished urethaning and waiting for it to cure
If you look closely, you can see the butyl rubber sealant as it snakes along the bottom of the windshield. The vent window is open so I can put
my arm through and position the windshield easily. The windshield at the A pillar looks worse of a mess than it actually is. After cleaning up
the butyl and urethane, the 1" wide stainless trim hides everything. Here's how to install the stainless trim page!