Back in October 2020, I made the decision to swap out the tired motor on my 1991 Miata. The car has done almost 213k miles on it's original motor. 199k of those belonged to it's original owner, Sally, who bought the car brand new in 1990. She lived just about 3 miles away in Point Richmond in Richmond, CA. Amazingly, in the three decades that this car has been around, it's never been registered outside of Richmond.
Sally was a really good first owner. She did regular maintenance - spark plugs, timing belts, coolant flushes, oil changes, air filters, fuel filters - all like clockwork. When she sold me the car, she handed over almost 2 inches of paper stuffed in a manila folder. If I'm ever wondering if something's been done, it's right there in the receipts.
Unfortunately, Sally needed a double hip replacement and getting in and out of the car was getting problematic. She walked with a cane and instead had been driving a small SUV from a family member. She listed the car on Craiglist in 2017 for a "nice price". She didn't just get an email from me, she got a flood of emails from people all around. The car, as she told me, had to go "to the right person". She had a list of questions for each buyer. Some were too young and she expressed concern about a young person having such a small car with not a lot of safety equipment. Some people weren't mechanically minded or didn't have the means to fix it and she didn't want to see it end up in a scrap yard. After agreeing to meet me, I grabbed cash from the bank and ran as fast I could to meet her.
The car was perfect for what I wanted. My plan, unknown to Sally, was turn the car into an Exocet. The body dings, worn out clutch, sad suspension, bald tires, and oil leaks weren't a big issue. I did zero haggling, handed her the cash, signed the title, and promptly handed the keys to my friend Abhijeet who was proficient at limping a car with a failing clutch.
Watch out for this guy, he's mean.
We got the car home and I started analyzing my purchase. It had LOTS of issues. The clutch was absolutely knackered, the suspension was clunking all over the place, the top was in tough shape, and I don't think it had been washed since 1995. But it was complete and completely rust free. Even with all of its problems, it still drove like a Miata. Smiles from ear to ear.
I did the clutch on it, replaced the brakes (upgrades to 1.8 brakes), bushings, control arms, sway bars, wheels, and tires. All that work took place in my garage. Still planning on making it an Exocet once I got all the mechanics sorted. In the process, my roommate and I, who worked at the same business at the time, began commuting together in the car.
That's when an annoying thing happened. I fell in love with driving the Miata. I couldn't bring myself to rip apart Sally's car. One night, browsing Craigslist, I found a project Exocet for sale in San Jose. I drove down, bought it, and shipped it up to Richmond. Well, damn, looks like I have both! Most people here know that I've got both, so now you know why.
This last summer, thanks to COVID, I had plenty of time to completely redo the car's interor. I went so far as to take the dash out and rebuild most of the broken tabs in it. I also reupholstered the seats (next time, I'll pay a professional because that's a PITA), deleted the center console, put new carpet in, wired up headrest speakers, upgraded the rest of the sound system with an amplifier, added LRB speed door panels (with a custom door pad that I designed myself), had custom speaker surrounds made from CNC'd aluminum, and made a number of other small cosmetic upgrades.
The Miata has been an excellent car. It was my daily for the last 3 years (supplanting my Lancer Ralliart and certainly not replaced by my F-Type R). Unfortunately, I'd been feeling like the car was missing more than a few of it's ponies. It didn't have many to begin with (112hp in 1991) so losing a few wasn't great. I did a compression test and things came out pretty badly. To make matters worse, testing the #4 cylinder was complicated by the fact that a previous mechanic had stripped the threads on #4's spark plug and inserted a threaded insert.
So October rolled around and I finally made the call: new motor time. I looked at a ton of options. Everything from freshly remanufactured motors from various suppliers (terrible reviews) to K-Swaps. I did what anyone would do an made a spreadsheet.
Ultimately, I decided to go with a JDM 1.8 from a 2003 Miata. Other options, like rebuilding the 1.6 to my OCD specification ($9k) or a K24Z3 ($10k), were more expensive than my projection of around $5k for a low mile NB2 motor.
This motor was delivered in November. Why in February am I still not done? Eh, life and ECU's. As you may have read, my saga with VividRacing derailed the ECU process and lead to a severe disinterest in the project. I've since gotten some steam back though.
My process for this project has been fairly meticulous. Every time I touch a bolt, I take a picture, add arrows, give it a number, and put any parts taken off in a number plastic bag. That way, I minimize losing items and maximize my ability to go back and pick the project back up later.
Bit by bit, I've been picking my way through the engine. Replacing seals, water pump, gaskets, and anything that might some day leak or rust.
I even went so far as painting the coolant overflow tank.
I also painted up the headers, the 01+ US intake manifold, and the valve cover.
One of the odd things about this project has been having to piece it together. There are a lot of great guides online about what parts you'll need, but it's full of decision trees. The US 01+ manifold means a 99-00 fuel rail if you use the 90-93 throttle body. Unfortunately, I forgot that I had to clearance the manifold and pinched the first fuel rail that I put on. Woops.
Today I started on the throttle body - which is a major difference on NB Miatas. The location of the throttle body on the NB motor is slightly different, so to use the NA6 throttle body, I'll be using the FlyinMiata spacer. That required drilling and tapping two new holes in the manifold (using the adapter as a guide while it sits on the existing studs, then once tapped, removing the two studs. There's also a spot milled out on the NB intake that you should fill with epoxy or JB Weld to smooth things out, so I took care of that as well and sanded it off tonight once dry. Tomorrow or monday, I'll take the 1.6 throttle body off the 1.6 motor (which is still in the Miata with almost everything disconnected except the drive shaft and engine mounts), and put it on the adapter. Following that, I'll be putting a BMW throttle position sensor to convert this to 0-5V signal for Megasquirt instead of a simple "idle, not idle" that the NA6 ECU uses.
There's still along way to go on this project. I'll do my best to write more updates. I'll also be cleaning up the rest of the engine bay, putting some non-dented panels on, and getting the car resprayed once everything is done mechanically. After that, it's time for a roll bar and some chassis bracing.