Why not make this as a cap to be sleeved on top of the original? Would think NOT cutting the original tower is better than cutting it …. Unless completely rusted away.
I would be interested in purchasing a set of these if they fit over the original tower cap.
I agree that for a company making parts for our cars that replace the originals in fit and function, it makes sense to make these replacement tops for the rear shock towers like the originals. For those who would like to restore their cars to as close to factory originality, this is the part to use.
But, as we've seen, this design doesn't always last 50 years, indeed the very first issue of the CS Register newsletter from 1980 mentions the failure of the rear shock mounts being a problem when using Bilstein shocks. So it seems that in some cases the failure has happened in less than 10 years.
These new replacements seem to be made of thicker metal, hopefully made of stronger steel, so they should be longer lasting.
The method of failure for the original parts is that the large washer on top is spot welded to the shock mount top resulting in concentrated stress points which seem to cause fatigue cracks that grow over time until they meet and the shock is launched out the top of the mount by the weight of the car.
Welding around the perimeter of the washer will greatly strengthen this part and should evenly move the loads further out toward the sides of the mount instead of the point spot welds. It alters the look a little bit, but I think it's a good trade-off as it's being done by a lot of members already in an effort to forestall failure. The maker of this part is wisely leaving the decision to modify the part to individual owners. Making non-standard parts would reduce the number of people who would buy this product, IMHO.
These new parts are not designed to be put over an existing shock mount because that would not address the possibility of existing fatigue/damage of the stock mount which should be removed/replaced rather than covered. Let's be real. Just as pretty much every coupe has some rust issues somewhere, the rear shock mounts are all probably starting to crack by now. There are numerous posts on the forum encouraging owners to do preventative repairs to their towers by sad owners who didn't.
If you really want to keep things stock, an appropriate repair would be to drill out the spot welds, remove the large washer, and weld up the existing cracks at the top of the mount and then reweld the washer back on, with some extra weldment to strengthen things. But that's a lot of work that no one will likely do, in part because access is a huge issue for such work, and until they fail, we'd rather think of ourselves as lucky and drive on. The easier procedure, now that this part is available, is to amputate the old shock mount top and weld on the new one. Since our cars aren't daily drivers anymore, once repaired by any method, the shock mounts should last the life of the car, race cars possibly excluded.
Stacking two would also mean that there would be double the thickness where the shock mounts which would bring its own issues. For example, the shock loading would still be on the lower, now aged and probably cracked top of the original shock mount. While some of that load would be taken up by the new mount on top, the fit would likely not be perfect and there might be some flexing, causing a click or pop on bumps that couldn't be found. That would be annoying.
Oh, and for those wondering if it would be better to have a longer replacement part and replace the entire shock mount, that would be a much bigger task. First of all, the failure is confined to the top of the shock mount. The sides, and the inner fender that the sides are welded to have never failed, in my limited experience. Clean removal of the entire tower would be tricky, though a plasma torch would be a big help, and then you'd need to get the new part accurately placed and securely welded in. And the part would be more expensive to make and the company would have to charge more for each one to cover their costs as few people would buy it because of the difficulty of installation.
