anyways i've been working on my crap-tastic '99 Z1 Dropoff, trying to get some half-assed damper performance. The main task was increasing compression flow without loosing rebound control. So the valve assembly and pumping rod needed some surgery.
This model used the original SSV assembly which did not have a spring, but rather a tiny little stepped nylon washer which would tend to explode right out of the box. Also the step is rather small, which is what constricts the flow. So using an 8mm crank bolt plastic plug-thing, i machined it down to fit the ID and OD, leaving the larger step. Since this new valve washer is taller, i needed to bore the aluminum valve body shoulder a little deeper; otherwise the piece remains the same. Third was the steel washer with the 3 nubs (not pictured) which also control the compression flow; the metal was ground down between the nubs, increasing the flow area.
I found this setup caused alot of cavitation or squishy-foamy damper feel, very inconsistant and shameful. I then compared the pumping rod to a later model 2001 Z3, and noticed the later one doesnt have holes drilled in the mid-section, whereas the 1999 has 2, both 1/3 and 2/3rds into the travel respectively, so i went and plugged those up. Also the upper rebound port seems to be lower on the '99, so i then plugged that and drilled a new higher hole right by the piston head.
At this point, one damper was cured, and the other one still sucked; also rebound was fairly quick (probably because i increased the rebound port size). Since i was already using fairly heavy oil (ATF), i decided instead of plugging and redrilling the rebound port, i would instead make it adjustable. This was done by taking a 3/8" fine thread bolt, drilling the out the center, countersinking for pimpness uhh i mean to improve return flow, and tapering the end for a cool needle valve type effect. Then i simply thread the bolt into the top of the pumping rod, where the depth of the bolt determines the rebound flow; ie. tighten for slower rebound, loosen for faster....does the job and basically operates like Marz's other cheezy rebound controls.
So now rebound issues are cleared, but still getting some slurp from that same damper. So i figure some pressure might reduce the cavitation and keep the oil from flowing above the pumping rod (yeah right). So anyways, i take apart the preload knob assembly, drill the 8mm hole out to 10mm, put a 10mm chainring bolt sleeve from the top, thread the 8mm chainring bolt withan o-ring from the bottom, the o-ring gets squeezed between the two sealing the assembly, and then thread a shreader valve stem into the bottom of the chainring bolt (conviniently sized for the M6 valve stem i cut threads out from, see Ghetto Mods #548.79: Shiver air spring). Pump it up, holds the air, feels, uhh, ok i guess for an infuriatingly horrid damper design, and slap it on my Zaskar, to which encompasses the future instalment: Guetto Mods #35G7.A: Project Zaskar.
thank you for my time.
1- valve assembly, old vs. new (exciting isnt it?)
2- rebound control bolt and pumping rod assembly (arent i just so clever?)
3- Top cap and air valve (ready and willing to be torn off from the first ghost ride)