Bc make a sealed thrust bearing as part of there cambertops and are about $350 posted I believe

^Is that BC as in Buddy Club or BC Racing as in the silver coilover company that is sold by JustJap?

Bc Coilovers sold by justjap

http://justjap.com/suspension/coilove ... r-suspension.html?cat=186

* S13 BC Racing camber adjustable $269
* S13 BC Racing castor adjustable $329

They look ok. Price is nice. Wonder how 'generic' the shock shaft sleeve is? Though nothing a bit of machining couldn't fix. If my car was only for asphalt circuit use I would adapt a base height adjustable set like they sell for Z cars. They sell a weld on internally threaded collar that you weld to a severely cut down strut. I love this idea as you can set ride height independent of spring pre-load/droop. I believe the shock valving would be a bit out for dirt use since spring rates listed are quite heigh.

I had one of those weld-on collars on my stock 1200 struts. Worked a treat with the stock 1200 springs, only took a few minutes to adjust ride height. Or you could use $30 industrial shaft collars to set ride height where you want it, like more and more racers are using.

The strut top nut supplied with the BC tops is for S13 strut inserts. If you will be using 280ZX inserts they might not fit, depends on if they are multi type with various collars, or if the nuts are specifically for the S13 shaft. Almost for sure they won't work with the VN inserts which have a gigantic strut shaft.

Ddgonzal - sorry, but I wasn't referring to a threaded adjustable lower spring platform, I was referring to a 'base height' adjustable kit. You cut your standard strut tube down to about 2" long and weld on an internally threaded sleeve. The fully threaded coilover shock unit then screws into the sleeve, and a lock ring secures it in place at the desired height. The coilover shock unit also features a conventional adjustable spring platform further up the body - this allows for independent spring pre-load and ride height settings. Google 'base height adjustable coilovers' for more info - they are a great idea. The problem with conventional coilovers is if you set your car up on corner weight scales, the passenger side will be lighter, so you jack the weight from side to side side/front to back/diagonal etc to correct it - except then the spring pre-load is uneven and so too is the droop characteristics. Base height adjustables offer the solution here as ride height and spring pre-load are independent set.

So they are coilover shocks, and not struts? Are you planning on running them in the rear?

They are still coilover struts, the only difference is the coilover shock body screws into the strut leg for the additional ride height adjustment. I'm having trouble trying to upload pics via my iPhone so you may have to look it up for picture reference. I'm not planning on running them on the rear as it only applies to coilover (or adjustable spring) type setups. For the rear of say a 910 Bluebird with a factory live axle coilover setup (Aus spec), a 'base height adjustable' style kit you would design it so that you would have an adjustable jack screw above the bottom eye bolt as well as threaded lower spring seats. The jack screw would be like those on an adjustable lower control arm with left and right hand threads for easy on car ride height adjustment. This way the car can be lowered or raised by the jack screw rather than the spring seat. Pre-load on springs has a huge effect on droop and the effective spring rate ie: a compressed spring has a higher poundage. Open wheel race cars have inboard coilover shocks operated by pushrods/pull rods for this reason (*note* also for rising rate rocker ratios for aero loads and to get the shocks out of the airstream). A leaf sprung rear end could be shimmed (where you would put lowering blocks) on either side for corner weighting. This wouldn't effect the spring rate as the leaf stays the same, only ride height changed. Corner weights being even across the front of a car are more important than the rear generally speaking.

How much droop and how much spring pre-load you want depends on numerous factors. Lots of droop will allow the spring to press the unloaded tyre back onto the road. The downside with lots of droop, particularly on the front of open wheel racing cars, it tend to exacerbates the problem at the rear and the car may pick up an inside rear driven wheel - resulting in wheel spin. This is why you want lots of droop on the rear of a car with an open diff, and why you can often limit the front a little bit. A normal coilover setup will compromise this setup because of differing corner weight heights will alter the droop/spring rate. Experienced drivers would most likely notice the difference, though not the average kid.