I'm finished reinstalling the mount. Took about 15 minutes being careful to center and tighten everything up just right. And this was with 40mph wind gusts and drizzle! (yes, my car was outside, and no, I did not think ahead).
I took it out for a 20 minute test run. The things I can say for sure is that nothing is broken, apparently no harm has been done. I held up the passenger side of the engine with a jack and a small block of wood on the passanger side of the oil pan, where it seems strongest (because of the creases in that area of the pan). While it wasn't holding up the whole car, I was worried about denting my pan. It didn't happen, so that is good.
I guess this little project was to evaluate two different things. One was: Does windo weld work for this mount? The second was: If it does, does it do anything to hold the engine in place better.
On the first point... I cleaned up the mount pretty good before applying the windo weld to ensure good adhesion. I filled in all three voids, the two large ones on the front and back of the mount, and the thinner slit on top. I let the mount cure for about 16 hours (about 3 hours in the sun 70 degrees ambient, 4 hours by a dehumidifier, and the rest under two 75 watt lamps about 1 inch from each face of the mount). The windo weld was still soft on the inside on the larger voids of the mount. But it did appear to have a relatively tuff skin.
Upon reinstalling the mount (putting the engines weight back on the mount) the windo weld seperated from the top part of the slit on the engine mount. The other two voids, held together.
After driving the car around for about 20 minutes, the bigger voids held together, and I did not get any seepage of the wet windo weld from under the dried skin. I didn't beat on the car, but I did imitate rush hour traffic at a slow crawl, which is pretty rough on this car's mounts.
As far as what I think of windo weld as a material, it still feels pretty soft when dried. I was playing around with some of it that had completely dried on the caulk tube, and it felt somewhat softer than the actual rubber of the mount. Almost like silicone caulk, maybe a bit stiffer. Being since it was described as a polyurethane, I expected it be stiffer than the rubber. It does seem very resilient though.
Would I use windo weld again for this? At this point, no, not for this particular mount anyway. With the huge voids this mount has, it takes way too long to cure fully. I'm wondering if it will ever cure since that windo weld on the inside of the mount still probably feels like it is inside the caulk tube. If these voids dont burst, then maybe in a few months things might get stiffer inside there, but until then who knows. My guess is that for mounts with much smaller voids this might work better.
On the second point:
After driving the car around for 20 minutes I want to say it solves all my problems, but truthfully, knowing that the windo weld is still wet on the inside makes it kind of hard to come up with any fair conclusions. It kind of feels a bit more solid between on/off throttle transitions, but after doing the work myself, it could be me just wanting it to feel better. I may have to drive it for a week or so and see how things go.
On the plus side, if this doesn't work, I will probably be able to dig out the windo weld should any inserts be made for this mount. And I already know that removing the mount is not too difficult when your being careful.
I'll update you guys in a week or so. Sorry for the long post.