I have a 1979 280zx with the power reciprocating ball steering box. Also, I have tokico lowered springs, tokico shocks (adjustable on front), eibach swaybars, bump steer spacers, adjustable eccentric front control arm busings, and techno toy tuning adjustable tension compression rods.
Here's a little info....
S30? manual rack and pinion is 2.7 turns lock to lock
79-81 power reciprocating ball steering box is 2.7 turns (16.3:1)
82-83 power rack and pinion steering is 3.2 turns (17.8:1)
79-83 manual rack and pinion steering is 3.5 turns (19.6:1)
Rack and pinion is the preferred choice for performance cars and racing, mainly because it offers better feedback when compared to steering boxes. Also, I believe that it is a little lighter and simpler and the unit is mounted lower on the chassis. I've read here and/or on zdriver that people think that the power rack and pinion units Nissan offered for the 280zx are junk and/or are too loose and/or sloppy.
First I want to distinguish between slop and lower ratio steering. Slop can come from any steering joints, couplers, bushings, rod ends, worn rack/box teeth/gears, etc. while a car with a lower steering ratio may just feel sloppy because it takes more turning of the steering wheel to get the tires to turn the same amount as a car with a higher steering ratio. I'm not exactly sure what the posts I read were referring to. The slop I'm talking about is like the extra play you feel in the wheel, ie. go drive an old truck....if you just made a lane change you'll have to move the wheel 15 degrees back before the wheels even start to straighten back out. That being said, what are you guys with power r+p experiencing?- please give details; what year car, tie-rods good and tight, steering shaft coupler good and tight, good alignment, etc.
Jeff Winter with Rallye/Sport has done some work for me and has been a great resource throughout the years, so I gave him a call. If you don't know him, he has been building successful race cars out of older Z's and 510's with over 30 years of experience and recently built up a 280ZX racer. I'm going to post about 280ZX rear suspension mods with his take on them and some links to his bragging rights. Anyway, he hadn't heard or at least couldn't comment on the 280ZX power racks being junk. The 280ZX he built had a power rack and pinion with the power removed. He said that steering ratio and power assistance is really all about driver preference. He also recommended I get a used unit from the junkyard or wherever and not to spend the money on a remanufactured unit....just flush it out good with p/s fluid. For me, I like harder steering effort and higher ratio's on the track (I have a really small Grant steering wheel), but I don't want to sacrifice drivability on the street, so unless my mind gets changed from replies to this post, I'll be going to Nissan's 17.8:1 280ZX power rack unit.
If you have something to add please be detailed with your reply.