Oops, another one - because this place clearly needs another NA Miata build thread

Or not, but it's too late now .

It's about four years since I sold my last NA, which I swore would be the last one I would ever own. Same thing with the one before that, and the one before that. Oh yeah. And the one before that. Clearly I'm good at sticking to the resolution of never ever buying another NA Miata.

This one came about in a somewhat roundabout way - the Miatas at Laguna Seca "hey, it's only a few weeks until the registration opens" email dropped. I asked my wife if she wanted to go as we had attended before but had to skip last year and she said "yes, but I don't think we should take the ND". Ah well, guess that means I have to go shopping then.

The parameters were simple - I wanted to start out with a nice example, ideally unmolested and straight. Finding somewhat bent ones with welded diffs for cheap isn't hard out here, but the nicer cars either got snapped up quickly or the people who were trying to sell them couldn't be bothered to actually, like, do any selling. Oh, and it would be nice if I could find a white one.

On a hunch I followed up on a CL ad with no pictures that appeared to be written by a literate adult. Car and owner sounded good over the phone - between the owner I bought it from and the previous PO who was a friend of the seller, together they had owned it for 22 years. I decided to take an unusual risk, grab cash and make a Sunday trip into the wilds to look at said Miata.

Got lucky that I managed to find a U-Haul car trailer locally as the local U-Haul was close to out of any type of trailer other than car trailers.

So what do we have here?

A rather dusty 1990 base model Miata, that is. Power nothing, no AC either. 113k miles on the clock with a documented timing belt change at 106. It looked bone stock at first glance other than the rims, but it's got a couple of aftermarket accessories that I'll probably remove, plus what feels like a proper LSD - well, the seller does live on a dirt road and thought it would be rude to not demonstrate the LSDness. Heck, it has an unbroken air guide and undertray!

It has had a good quality respray so no flaking paint on outer surfaces. Roof looks OEM and serviceable, but I suspect it's been replaced at least once. Minimal lifter tick on startup, revs little the happy little 1.6L it is, decent oil pressure.

So what's the plan?

First, do a bit of catch up maintenance - it needs surprisingly little, but the gearbox tells me it wants MTL, the shifter will want a rebuild, the window regulators want attention, the tired glow worms in the front want replacing and it needs a good clean. Oh, and I need to check over the brakes as they look and feel like they won't be long for this world. Standard stuff I've done a bunch of times on Miatas.

Second stage is going to be getting the car trackable and add some reliability mods:

• Rollbar is high on the list. Really liked my Blackbird Fabworx GT3 so I suspect there'll be another one ordered soon
• New radiator - the old one is slightly bent and while it doesn't leak I don't trust something like that on the track. I'll probably go oversize for N/A with something that's good enough to track even with a turbo.
• 1.8L brake conversion. Because I want to, and because there is likely more power in its future.
• Suspension - it doesn't feel like it but at this mileage I expect it to want bushes and shocks. Looks like I'll be turning to FM for that - probably going to keep it simple and put Konis with lowering springs on it.
• Spruce up the interior a bit and hopefully source a hardtop
• Do something about the ugly Momo wheels on the car
• Put in the Momo Prototipo

Third stage will involve boost. I'm pretty sure I want to go turbo after having owned a turbo NA (badly built by a "forum expert") in the past, but do it right this time. As I don't want to piece anything together, this is likely going to be another expensive call to FM.

The alternative third stage would involve a high compression 1.8 swap and ITBs, because who doesn't want less power for more money?

That looks nice Tim! You’re making me reconsider changing the color of mine & keeping it white. 

Thanks, Pete! I'm not normally a big fan of whit cars but for some reason, it works for me on a few Japanese cars - 240Z, old Skylines and, well, Miatas.

I do have some ideas about making it less monochromatic though, which is usually my problem with white cars that have a black interior.

You know, that email from the Laguna Seca event was only supposed to remind you to register.

Keith Tanner said:

You know, that email from the Laguna Seca event was only supposed to remind you to register.

Are you sure there wasn't a subliminal message in there that required people to buy more Miatas? I'm pretty sure there was... .

Went to the local AAA office last Monday to get the car registered. Even though our local DMV doesn't have massive wait times, my wife had suggested I'd try AAA as it looked like there weren't many people in line when she went there. She was right, I think I had the car registered and plated in about 20 minutes. Also gave it a wash to celebrate the occasion.

Yesterday was mostly spent in an attempt to clean up the car and further assess its condition. As mentioned, it has a bent radiator and the top plastic tank is started to discolor, so the radiator went up higher on the list than it had been before:

Definitely looks like something hit the radiator, plus it does look rather second hand anyway.

The first batch of aftermarket parts also showed up, would've been rude not to put them on - Garage Star front license mount and Delrin door bushes.

I can haz front plate:

The Delrin door bushings look more or less the same as the OEM ones, only that they're not squishy. They're also super easy to install.

Big part of the afternoon was spent with the shop vac and a newly acquired steam cleaner. The car was pretty dusty and the seats had a few stains, so I figured it was worth it trying to turn the interior into a nicer place to be.

Driver's seat "before" - the passenger seat had already been steamed, scrubbed and vacuumed at this point:

After:

Not Cousin_Eddie levels of detailing-fu, but it's a nicer place to be right now and has less dog hair in it. The latter is kinda important - as much as I like dogs, I'm allergic to dog hair.

It also looks like the passenger side fender has been replaced, but whoever did that did a good job - it fits almost better than the original one on the driver's side.

Next steps are pulling the wheels to have a good, hard look at the brakes and also poke around under the car. I did mention that it feels like it has an LSD, but I have no idea what's under there. Plus there appears to be a slight oil leak from somewhere underneath there, too.

Driving it around the neighbourhood after installing the bushings does suggest it's less rattly from the door areas, so the Delrin bushings are doing something. Driving it around again also reminded me that the gas pedal isn't quite as positioned as I'd like it to be for heel'n'toe, so the FM pedals just went on the shopping list. I'm almost ready to order the rollbar as well, assuming that I can get a reply from a seller on Clubroadster regarding an interior "upgrade" he's selling...

You mentioned replacing the radiator with one that has some headroom for future upgrades. I used this one which I bought from 5X Racing. I can't say enough good about it. I'm very happy with it.

In reply to Cousin_Eddie :

Thanks, that's great feedback. The CSF radiator is one of the three I'm considering, the other one being the FM or SuperMiata crossflow rads for the additional cooling capacity if I go turbo. I was originally pretty hell bent on going turbo, but right now am reconsidering with the recent, CARB-only announcement from FM. Not that CARB is a bad thing (and I think I understand why they made this change), but I would've preferred one of the original packages that included bigger injectors and aftermarket engine management.

Unplanned purchase #1 showed up. I knew I wanted white wheels on the car for some reason, and I like TE37s, so the plan was to acquire a set of 15" TE37s. Until I found something a little more unusual during a sober (!) late night ebay browsing session. They're Bridgestone Super Raps, and while they look like steel wheels, they're actually aluminium wheels.

Got home from work just in time to pull the wheels out of the box and mock them up on the car:

Let's see what they look like when properly bolted to the car. The tires on them are rather well used, but should do the job for testing the fit while I try to procure suitable 14" rubber.

Today was the day to jack up the car, take the wheels off (boy were those heavy), crawl underneath and see what I would find.

Things looked depressingly stock when I took the wheels off:

Everything looks OK, but in need of cleanup or replacement. The rotors have a noticeable, but not too bad lip on them. Bunch of surface corrosion from standing around, too. Obviously the dust boots around the shocks have had it for a while now, but the shocks look like original ones so I'm guessing they decided to call it a day about 70k miles ago..

However - and I apologise for the quality of the photo, I took a video of the area but no decent photo - look at those "frame" rails:

I don't think I've owned a Miata in the past decade with "frame" rails this straight that don't show any marks of being used as jacking points or involuntary encounters with speed bumps. Colour me impressed.

Oh, and there would be more if the Photos app on my Mac could decide if it wanted to eat my library right now or actually just shut down so I can restart it and get at the remaining, freshly imported photos. It's been one of "those" days.

Looks like the Mac decided to release the Photos library after all, so here's the second part.

So far I'm pretty happy with what I found. There's evidence of a small oil leak (the transmission has a thin oil film on it, nothing major). I'm currently hoping that it comes from the valve cover gasket and not from the rear main seal. Even the clutch slave cylinder seems to be behaving itself.

I also decided to clear the roof drains. Unfortunately it had rained before I pulled the car into the garage, so I got the gunk that came out of them all over me. Yay.

This diff doesn't look like a 1.8 Diff to me. I think this is another "depressingly stock" part, but I'll deal with it later. It does, however, show that I really need to take this thing to the local self car wash and give the undercarriage a good blast.

Hmm, the diff appears to have some number printed on it?

Oh, and I'm not super impressed with the exhaust either.

I also found a little more rust. Probably wants treating sooner or later, but I can't say I'm unhappy with the level of rust I'm finding.

But I doubt that anybody wanted to see any of the pictures above after yesterday's wheel teaser .

No, I don't have a Miata problem, I can quit any time I want.

I'm not 100% convinced regarding the wheel choice, but IMHO they're an improvement over the Momos. Plus, they have been growing on me over the course of the day. Let's see if I decide to run with this theme or if I "need" a set of 15" Wats/BR wheels.

The wheels seem to fill the arches nicely if you discount the current 4x4 stance. Mind you, those tires are 195/60R14 and not the 225/50R14 I'm planning to run. I'm hoping I don't need bolt-on arches for the latter.

Let's see if the weather behaves tomorrow so I can attack one of my "favourite" jobs - attempting to fix the manual window regulators. Unsurprisingly they're stiff and the windows really don't want to come down much further than 1/2 way.

The "painting by numbers" continues. One of the advantages of having had a few of these is that the basic jobs just naturally flow.

Speaking of naturally, naturally the window regulators needed attention. I knew that - during the test drive, I was worried that would break the passenger side regulator. That's how stiff it was.

Interestingly enough, no matter how often you do a job, there's always more to learn. For example, I didn't know that unclip the window cranks by essentially pulling a piece of fabric in the gap between the handle and the door. Much easier than the two-screwdriver-and-hope-you-don't-damage-the-door-card approach.

Assemble the deluxe lube kit:

The Sil-Glyde is a decent alternative to the often recommended Honda Silicone lube (to be used for the rubber channel that the front of the window sits in). The Super Lube and the cable lube aren't strictly necessary, but I find the Super Lube easier to apply to the bottoms of the metal channels. Due to the curved nature of the channels, the spray lube usually doesn't get there, and it's the area that's usually full of old grease.

More good news, both rear window bushings were in good shape:

The two metal channels for the window were full of gunked up old grease, but it came out easily.  The front rubber channels were mostly dry with a side of dirt. Didn't take long to clean them out and re-lube them.

Also, some additional good news in the form of decent speakers already mounted in the doors. Not super impressed that they don't have any form of rain cover over them inside the door, but that should be relatively easy to rectify.

Halfway through, somebody showed up to check up on the work and point out the continuing lack of rollbar:

Not so pleasant surprise on the passenger side - no vapor barrier. Well, there are remnants of one, but no complete barrier and unsurprisingly, the fiber board on the door card was damp as it had been raining overnight.

I can live with that right now, but I need some of the adhesive used for these vapor barriers so I can make one.

All in all a successful day. Windows are rolling up and down nicely now and I finished the job just in time before the next rain arrived.

As this car is a bit short on LSD goodness I've been looking for a proper Torsen. Found someone semi-locally who's breaking a low mileage 2004 NB2 that is supposedly a 6 speed/Torsen car.

My understanding is that this would give me the same rear end ratio as the current on in my NA, but with the stronger Torsen 2 diff. I also found a post from Keith on m.net that states the whole rear NB subframe is a bolt-in affair on an NB but with some minor differences in bracketery. Plus obviously the 5mm wider track on each side.

Question now is - do I pay the guy the additional $200 he wants if I get the whole subframe with diff?  Keeping in mind that I probably need to convert the brakes back to the "regular" 9.9" rotors - I don't think I can run NB Sport rotors under the 14" wheels.

Sorry if this is a newbie question, last time I did swap out a diff I did get the rear subframe with all bits and paid a local shop a few GBP to drop the whole thing in.

And if I could read, I would've noticed that the NB2/6 Speed has a 3.9 ratio and I need a 4.3. Research, do it first and do it properly.

You'll need axles anyway, and odds are they will be seized in the knuckle of either your car or the donor - so I'd be inclined to do the full subframe swap. Your diff is definitely an open 1.6 diff, based on the axle ears.

Someone correct me if I'm wrong, but I believe that '04 is a Tochigi-Fuji, and not a Torsen. They're a different design and aren't nearly as robust, according to the internet. 4.30 Torsens are pretty uncommon, 4.10s seem to come up much more frequently and are pretty close ratio-wise.

I'm pretty sure you're correct about the 04 having a Tochigi-Fuji LSD. I think all the NBs do. The attraction was that the NB1/5 speed LSD apparently has the same rear end ratio as the NA6 one, but of course I hit up someone who has an NB2 he's breaking. Which is OK because I still want the seats, but I definitely don't want to burden the anemic hamster under the bonnet with a 3.9 diff.

The T-F diffs started in '03, so you can get a 4.30 Torsen from a '99-'02 5 speed. The hard part, of course, is finding one.

Good call on the NB2 seats. My favorite stock Miata seat as well.

Apparently my ability to find semi-unicorn parts is undiminished. Looks like I've got a line on a 4.3 Torsen already...

Gah. So the seller of the diff messaged me last night that he's damaged the axles on his car and needed the axles that were supposed to come with the diff, but is more than happy to sell me the diff without the axles for the same money. Eh?

Otherwise it's been a quiet week on the NA front, other than putting the old wheels back on as they actually have tires with some tread left. Gotta figure out if those Momo wheels are actually worth something before I punt them out for a few bucks on CL.

Does anybody happen to know if the front bumper cover is different between the NA6 and NA8? Amongst my parts stash for a rainy day, I found a front lip that I think is an R package lip replica. Doesn't appear to fit the bumper very well, though (as in, fits like crap and looks like it's a bit too big). I'll probably just go with the original plan of using a genuine GV lip, but I'm curious.

Not much else to report, the parts acquisition phase continues, gotta grab them before the hoarders do, right?

I finally got to drive it a bit more - I think the tires on the original wheels are out of balance, plus the suspension is worn a little. Also, the tires are old (like, then years old) and the wheel with the worst vibration is missing the hubcentric ring. Nothing that I didn't expect. What I wasn't to happy is the brake efficiency - hitting the brakes hard when there was nobody around and I managed to lock up one wheel. Might have to spring for refurb'd calipers.

Maybe some new brake hoses while you're doing the calipers ?

New brake hoses are definitely on the to do list.

Lookin' good so far!

IIRC the 'R' model lip fits all NAs.  I've got an eBay version on my '92.

The vapor barrier: i use landscape plastic and duct tape. Not factory, but cheap and damned effective. 

In reply to Dusterbd13 :

This deserves an award of some kind.