JMortensen

Do you have any adjustable suspension parts? Control arms, camber plates, camber bushings, etc? Stock you can shim a tiny amount of caster in the front and set toe, and that's it. You can do that yourself, not even worth taking it to an alignment shop, unless you just want to see how bad it is.

You could try to track down my ex-roommate Larry Butler. 510 guy, was Nissan master tech, worked at a Z shop in SLO in the 90s. Lost touch with him, last I heard he lived in Atascadero, but I'm sure he's still turning wrenches and the guy knows old Datsuns backwards and forwards.

Yeah his Datsun project is basically putting his Enviate hill climb chassis under a very modded Z kinda sorta shape. It will be badass, and there won't be very much Datsun left.

Sounds like a badass swap to me. My understanding is 325 whp is pretty easy to do NA. If you start thinking that isn't enough power, turbo it and make ridiculous power. BeastieHatch has a J swapped Civic and it's putting down 600 to the front wheels (now has electric motors on the rears too). https://www.turnology.com/features/beastie-hatchback-the-v6-turbo-powered-civic-to-end-all-civics/

I think the strongest argument for it is the way circle track racers will adjust their crossweights to make the car turn left better, because they don't give a shit about turning right; what improves one hurts the other, so getting them balanced or close should make the car handle turns in opposite directions more equally. Also see this on rovals, where they'll set road race cars up to handle on the oval portion because it's higher speed than the infield and results in better lap times overall. https://grassrootsmotorsports.com/articles/understanding-corner-weights/ Would be interested to hear how far off yours were and how big a difference it made after fixing it.

Stock LCA is 14.5" IIRC. Pretty sure on that. On mine I made the control arms 15" long, left the axles stock, and I have my camber plate tops flipped around to reduce neg camber in back. I had pretty stupid amounts of neg camber with the ride height that I have.

Re: ride quality. I took my dad for a ride in my Z with 200/250 springs, camber plates, heims jointed fronts and TC rods, and Illuminas on 1 back when he was about 75 or so. His comment: "Seats are comfy!" With respect to camber change, what you're looking for is to keep the tread flat under load. With independent suspension, body roll = camber loss, so with soft springs you might be rolling over more than your static camber can compensate for, and then you roll onto the sidewall of the tire. You need more camber or less roll to keep that contact patch flat. If you have the camber right you should be a little hotter on the inside. Adding caster helps as that will give you more neg camber when the wheel is turned, but you'll have to trim your airdam/fender if you haven't already. You seem like you are already past this stage, but for other people who might stumble in here, you can use a dab of shoe polish running over the edge of the tire onto the sidewall in 3 or 4 spots to see how far you're rolling over onto the sidewall. Inflating the tire more keeps it from flopping over as much but also hurts grip if you do it too much. Better to adjust the camber so that you can run the optimal pressure for your particular tire. You're wrong about the camber going negative when the control arm goes past level. It's when the control arm goes perpendicular to the strut tube that you would actually start to lose camber. This was pointed out to me many years ago by blueovalz, who built a really awesome Z here, then sold it and moved on and no longer posts. You can confirm this with Dan McGrath's post here, in what is IMO the best thread on the whole forum:

There are problems with all of these solutions: Bolt in camber plates won't move enough to get you the neg camber you need for autocrossing (I think you'll find 2 degrees isn't sufficient unless you're running all season tires and not real serious about it). Stickier tires will create more roll which requires more neg camber. Camber bushings with delrin/aluminum don't allow the control arm angle to change, which it HAS to do as the suspension compresses. TC moves in an arc, so the control arm should have some front to back movement available. Some of that might get taken up in TC bushing flex, some in crossmember flex, but it's not ideal. Camber adjustment with these also adjusts bumpsteer. Moving the xmember pivot requires removing the washers that are welded to the xmember, which is tough to do without screwing up the thin xmember metal. Moving them out will gain you some camber, but you can't go too far before you run out of threads on the tie rods. I slotted my xmember and found that moving the pivot up about 7/16" minimized bumpsteer. The old JTR recommendation was up 3/4, out 1/4, which is too high on the bumpsteer for my car, and still not enough neg camber. Longer control arms will have the same problem with the tie rod threads. My suggestion would be a better camber plate like Ground Control or TTT. This will allow enough movement to actually get the camber you want without worrying about the tie rods. The tie rods used to be more of an issue, because one of them is LH thread 14x1.5, which is tough to find taps and dies for when making your own, but now there are several vendors selling aftermarket tie rods. If you get new tie rods with a turnbuckle, that basically doubles the amount you can adjust before you start getting too close to the end, and that frees you up a bit. If you go with replacement tie rods, then my second choice after the good camber plates would be custom LCAs with the heims joint inner, and you can decide to make them longer or move the pivot. Moving the pivot would have the added benefit of being able to adjust the bumpsteer. EDIT TO ADD: if you're worried about the 14mm shaft on the top of the Tokicos in combination with monoball camber plates, Ground control makes bushings to fit them in a 5/8" monoball. I'm sure TTT does the same.

I think you're missing out here, regardless of whether you do it diagonally or setting fronts even. Mine was really far out. I'd be shocked if fixing this didn't help.

There are SO MANY other things that could affect it, that I think your results (and mine) aren't really meaningful for other people. The thing about the Miatas is that they have a tendency to lock up the LF tire under braking. Not sure that I've heard anyone say that about their Z. FWIW I learned a new trick the other day: when corner weighting, set the front weights equal, rather than setting the diagonals even. This is supposed to load the front tires more evenly under braking. Between setting the fronts equal and making the lines equal length, you MIGHT be able to tell the difference. Probably not... To me these are things that you do when you're building because it's theoretically better. The actual difference it makes is probably pretty minute.

I didn't think the position of the T made a difference either, but since I was plumbing it anyway I went ahead and did it as evenly as I could.

I read something on Miata forums about the length of the hard lines being different, and this contributing to their tendency to lock up the LF tire, so I tried to put the Ts in the lines right in the middle. But yeah, T the front lines and go to the front master, and T the rears and go to the rear master.

Since you mentioned bumpstops, what kind of bumpstops are you going to run? They're actually a very important part of the suspension, and most people with Zs run hard, crude, polyurethane from Energy Suspension, which suck donkey balls. I would suggest if you don't already have them you look at some of the longer, more compressible ones like Koni or FatCat Motorsports sells. They act more like a spring than a piece whose only responsibility is to keep suspension parts from slamming together.

I wouldn't think it would be a problem if you have a needle bearing in the top hat already, but since it obviously is, bearings on the springs should help.

It's pretty common for the spring to wear on the coilover sleeves. The problem is worse when you use longer springs. The longer the spring, the more it deflects. Bearings under one or both ends of the springs are a good idea as they help the spring to compress with less friction and will allow the strut to rotate more freely. https://www.ebay.com/itm/Strange-S1409-Spring-Seat-Bearing-Kit-2-pack-Torrington/123588766568?hash=item1cc676eb68:g:SvYAAOSwNm5ZsbJl