I have a set of KW Variant 3 coilovers that I acquired for my S14. As you may or may not know, these do not come supplied with top mounts of any kind. If you search around the intrawebnets, you'll find that most people with these coilovers are using Tein pillow mounts. The reason most people don't go with KW tops is that they cost at least $1000! It's easy to see why people go with Tein.
Now, if you talk to either KW or Tein about this setup (which I've done, by the way), they'll both tell you that they can't recommend it. The KW V3s are designed to be used with the OEM top mounts and the Tein pillow mounts are designed to be used with Tein coilovers. So neither company will tell you, "Sure, that'll work." Everyone online however, will tell you otherwise. So I went ahead and got the Tein pillow mounts.
From your intrawebnet searching, the only issue that appears to be common with this setup is that the supplied spacer that goes under the front pillow mount is too tall. It comes from Tein at 15mm and most people cut it down to 7mm. This seems to be a pretty good height as it prevents the pillow mount from making contact with the top perch of the coilover without wasting a lot of space and not giving you a enough engagement with the through-nut. Even with this modification, the top of the piston rod does not thread all the way through - more on that later.
Once you get that taken care of and start assembling the fronts, you come upon the next issue that wasn't quite as apparent from the threads you've read - torquing the top nut. The KW specification is 26ft-lbs which doesn't sound like much, but it's very difficult to get to that without the piston rod spinning in the body. Back to the intrawebnets you go. You'll see a lot of people telling you to grab the rod with vice grips or pliers - this is a bad idea as the potential for damaging the chrome finish is tremendous. That sort of damage will result in premature corrosion of the rod and ruining the seals at the top of the shock body. Another thing you'll see is people telling you to just hit it with an impact. Again, this is not recommended as it could damage the seals or the valving inside the shock body. I've tried strap wrenches, nylon straps, tape with pliers, installing them on the car and torquing them under load - nothing is working.
The main problem here is that the piston rod from the coilover was not designed to pass through such a deep mount. The bearing in the factory mount is about 14mm deep. The spherical bearing in the pillow mount, on the other hand, eats up 22mm of depth just by itself. When you include the bottom spacer and the through-nut, you've got a depth of almost 40mm! So even though the top of the threads on the piston rod is flattened on both sides so that you can get a wrench on it, it does not pass through far enough to grab it.
I have been told about this tool from Lisle that is supposed to hold the piston rod while you torque the nut with an offset wrench, but I can't seem to find how this works or if it will even get the job done on this setup. My suspicion is that it will not.
At this point, I'm faced with either trying to use one of the forbidden methods (probably impact) to tighten these, or I'll have to go back to the machine shop to shave more height out of the pillow mount. Some of the ideas I've had: turn the shoulder of the through-nut down and cutting the bottom off the same amount, cutting the hex head of the through-nut down, shaving some of the top spring perch down, and ultimately it would need to be a combination of these in order to get enough height removed to get the top of the rod exposed. It seems like a lot of work and it would probably end up costing me another $50 to $100 to have that all done.
We haven't even discussed the rears yet...
I haven't seen a single thing on the world wide webs about issues with the rear mounts. Again, these were designed to mount to the OEM tops and the rear spring perches fit quite nicely that way. The Tein pillow mounts on the other hand are quite a bit wider so the perch has zero lateral load support. Also, since the nut supplied with the Tein mounts is threaded for their piston rods which is more coarse than the thread on the KW and OEM versions (1.25 vs 1.0 respectively). If you were to put this together with the parts you have, the only thing resisting lateral load from the springs is the friction from the contact patch created from the thin ring of aluminum on the perch with he machined steel surface of the bottom of the pillow mount.
Is this what all these people are doing?! Have they inspected this recently? Do they have horrendous banging noises from the spring smacking the piston rod when they corner? I don't understand how people run with this without issue...
I won't have this because I'm having an adapter made out of nylon to fit inside the spring perch and around the bottom of the pillow mount bearing support. I had considered having a whole new spring perch made out of aluminum that would fit around the bottom of the pillow mount like this perch fits around the bottom of the OEM mount; but after some consideration, I think the nylon adapter will suffice. Honestly, there isn't a ton of lateral load on the springs, so I just need something to keep everything straight in there. It'll probably end up costing me $40 for the pair - I don't even think I could get the raw material for new perches for that price. I'll let you know how this turns out.
If you have any experience or input on this, please feel free to chime in.