I see this latest 78 adventure began in January. This past weekend with temps in the 70s, I got out and finalize removing butyl (or whatever is was) from the body rear window frame. I also "fitted" the rear window with the original blocks. But, i quickly realized fitment isn't easy. So questions remain and hoping those that have been here before can provide their experience. You'll see from the images of where I am at.

With the window in place I see gaps.

• Should the window edge rest on the blocks?
• Or, at the bottom, the intent is that they do not rest on the blocks but provide a spacer to push/close the gap at the top.
• It seems the top blocks, the window ledge rests, while at the bottom they work to "push" the window forward and close the gap at the top?
• You'll see the trim tags not in place which will consume space and tighten that gap

The rear window in place


Window and the blocks...these are the original blocks or spacers

 

On my 78 I could find no evidence of any blocks at all when I took the window out. I don't know the history of the car so it is good to see what they should have looked like. I had nothign like that. When I got my parts from Zip 2 blocks were included but as much as I searched I could not find any info on where or how to use them. I found 4 raised sections in the fiberglass, 2 at the back and one on each side. SO I cut the blocks in half and placed them on top of the raised flanges. Not above them. I set the window down and it appeared perfect. Same distance at the top as there was at the bottom, and the same distance up from one side to the other. What can go wrong?
I will be glad to SHARE what could go wrong. The first thing I hadn't thought about was the side to side movement of the window. As I tried to get the caulk to set up by pushing on the glass I didn't realize I was actually pushing the window from the right side over to the left side. The blocks were holding the winow up from the fiberglass but they were not keeping the window centered in the opening. The other problem I had ( but didn't know it at the time) was that the more I tried to set the glass, the more it was being pushed up towards the roof. It had actually come off of the lower blocks. My mistake was I was trying to get the glass nice and tight at the bottom. I didn't realize it had moved until I tried to put the inside trim in place. The 2 lower corner pieces were too big by about 1/4" which means I have to trim them when I finally get done.
When they say once the glass is down it isn't going to move is correct. Not knowing about these changes as I put it down until it was down made everything OFF a little bit. I don't think you will ever get the same amount of daylight all the way around. In hindsight I think that if the inside trim was in place it would have helped greatly in getting the glass in it's proper position. I have left mine alone and have not tried putting the outside trim on until I get a chance to get it outside and spray it with water. If there are no leaks, I will leave it as it is and put the trim on and adjust the inside trim accordingly. If it does leak, I will be taking it all apart, and knowing what I know now, it will go back on perfectly. If you need an extra set of hands let me know.

 

I see how easy the window moves when resting on the blocks...I get this phase.

After reading your experience, I'm thinking here that what I should do is install the trim clips, set the butyl in place with the protective tape still in place, as well as the blocks...then set the glass down to see how it squares up. AT this point, figure out what adjustments need to be made, then take it all apart. Finally, do the final adjustments and only then and the primer, remove the tape and go at it!

From you're experience, will this minimize final adjustments?

 

First try leaving the interior trim in place and see if it helps keep the window in place, or close t it. Put the trim clips in, trial fit one more time. Prime it, put the butyl on the glass, set it down then try pulling the tape off at an angle, like peeling off a decal, while only lifting the glass a minimal amount. There are no FINAL ADJUSTMENTS after the INITIAL ADJUSTMENT! That is the downside of using the butyl tape vs sealant that the windshield guys use nowadays. Once it's set down for the final alignment, make some hash marks and make sure your helper knows what you want and where you want it. My son was helping me and he got it set down on the marks, but neither of us thought about the window moving side to side until it was over to the left. By then we couldn't move it. After the fact I thought that maybe making some wedges to go under the sides would have helped the glass slide down evenly. But I will worry about that if I need to take it off again. If not, it's the next guys problem, like maybe my son's!

 

I am going to take you up on your offer to help. Late September when it cools down further! BTW, interior trim has been removed but I don't see how that would help with fitment?
So I just looked at the ZIp kit...yeah only two blocks. Here are my questions:

1. Primer says apply to contact surface. Is that the glass are the body galley (for sake of a better word)?
2. You state place butyl on the glass. Does that make the body surround the contact surface?
3. If that's the case, can I not place the butyl on the glass and "fit" without taking the tape off?
4. What's purpose of hash marks?
5. I have six blocks to use...suggestions to deploy the six for final adjustment?

I already learned its not easy to lift the glass out of its groove. I suspect the butyl will "lift" it and make it more accessible?

 

I put the primer on the glass before I put the butyl on it and then primed the fiberglass flange around the window. I hadn't thought about pulling the tape off once the window was in place until AFTER i was done. The only hesitation I would have is the weight of the window pushing down. I would think you need some type of shim to hold the window up until you pull the tape.
I put the hash marks just to help line up the glass from top to bottom ( or front to back) and side to side. One mark on each side. Just to get things in the general area of where they need to be because as I said, once contact is made you aren't moving it much. As for the 6 blocks, I actually did fine with the 2 at the bottom pushing ti forward/up and the one on each side. Again, it was the side to side movement until the glass is pushed down far enough for the front corners to keep it from moving side to side. that I was not expecting.
As for the interior trim being in place what I learned was that as I was trying to push down on the back edge of the glass to make sure there was a good seal, I was unintenionally pushing the glass forward. By the time I got done the glass was really pushed down far in the back, I had compressed the butyl that much. Later, when I went to install the trim I could barley get the back piece in place because the glass was so tight against it. So I managed to get that big plastic piece in place, but as I moved forward inside the car when I got to the 2 corner plastic pieces and tried to line them up with the halo pieces, the cover pieces were about 1/2" too big front to back so when I get all done I might have to trim that 1/2" off the edge of the corner piece to get it to all fit. That was due to the large back piece not being able to go back far enough. My thought is that IF that back piece is in place before you put the glass in, it will keep you from pushing the glass to far down.
And the butyl will lift it up a bit but once contact is made without the tape you will not be able to lift it without destroying the seal itself.
I have done a lot of things on cars over the years, especially on my 78 but this window was the most stressful because there are no DO OVERS.And I was never able to find any good tips on how to do it except the You Tube one where the guy lifts the window over his head and then plops it down on the car while trying not to trip over the air hoses in the driveway! Added stress is that I managed to get the window out without breaking it, got is all cleaned up and moved around the garage without breaking it, but one slip up and I need to look for a $1500 window, all because I needed to replace some $15 worth of plastic trim clips! When you are ready to do this just let me know.

 

I appreciate the detailed explanations...helps to visualize the situation. I figure that the blocks on the side, with the window resting on them provides that gap side to side. Likewise, the blocks at the backend, with the glass edge laid against the edge, manages the gap at the top.

 

I have not done this but throwing a few things out.
The butyl rope comes in different thicknesses. Don't know what size this application takes. Might be critical.
Looking at my 78, am envisioning how I would do it. Not sure since all the trim is on. Will definitely take 2 people.
You mention pulling the tape off the rope later but isn't it paper type tape? Will it tear?
Every time I did a window the butyl rope went on the body and glass was set on it. Looking at the back window, wondering if the rope will tend to roll when window is lowered in place. Am sure you guys will figure it out but consider setting up a camera on a tripod to record how it is done. Good luck and let us know how it went.

 

The old butyl, was removed from the inside edge of the window and not the edge that faces downward. The butyl on the body (bulk of) was removed from the edge facing upward. I'm speculating here, but if the butyl is set on the body, it would seem the glass edge would push it downward, or roll as Rick describes it. Anyway, I played with the blocks. But a question back to kanvas, the trim clips: it seems that plug facing outward needs to be removed?

Here are some images of the blocks and their spacing. After moving around, it seemed the Zip blocks worked best on the sides to "elevate" the glass edge while the old blocks at the rear, provided a space for the gap at the top.

The blocks



The gaps




The trim clips

 

The butyl is supposed to go on the inside face of the glass, not the edge. When I finished my prep I painted black primer on the inside edge of the glass. A tip I got was to put masking tape approx 1" from the outside edge then paint on the primer. The tape gives a straighter, more finished look since you might see it from outside the car when finished. Once that dries I put the tape there and I believe you are supposed to start at the center of the bottom and work your way around the perimeter of the glass. That eliminates any seam at the top for water to get through. Then I painted the primer onto the inside channel of the fiberglass, as far out as the holes for the trim clips. Again, I put a line of tape to make it neater. If I recall correctly the blocks from Zip were not square but more rectangular, so if you flipped it it changed the positioning of the window. When done, my gap across the top is 1/2", the gap at the bottom is about 3/8", the gap on the right side is also 3/8" and the gap on the left side is 1/4", due to the window moving as I pushed it down. At the very corners the gaps to the fiberglass are smaller, but that is just hwo they end up. As for the clip, you don't trim anything off. In my pic the fatter end goes into the holes in the car. The thinner part then gets pushed in so it works like a normal push pin body clip, expanding the 4 split tangs that are now inside the car.