I'm not dead, and this Miata isn't either. I hope. The machine shop took their sweet time getting around to finally working on my engine. I have had so much else to do that I managed to not get too upset.

Someone cut me off while I was driving my Jeep at night, in the rain. It took a hell of a fight, but I managed to avoid a salvage title and their insurance paid out after over a month of back and forth.



Thankfully the damage to the unibody was extremely slight. I did a bit of bodywork to pull that back to straight with a hammer, a c clamp, a block of wood, a ratchet strap, and a tree, and you'd be hard pressed to tell it happened now. Well, if you removed the mismatched fender and grille. I'll get those painted at some point.

I rebuilt a transmission.



And after years of preparation, I finally manual swapped my XJ. Not being able to shift my own gears for months was lame.



Of course, being an old jeep, I also delt with lots of other problems after 5 years of pretty trouble free service. That kept me busy for a few weeks.

I eventually was running out of other projects, and finally planned to march up to the machine shop and tell them my engine was leaving with me in a week, either machined or not. He foiled my plan and told me it was happening within a week, so I left happy. I got the call that my block was done just before Thanksgiving.



I put it on the stand and ignored it due to the holidays. And because my air compressor was broken.

Last night I finally took the time to fix that.



One of the contacts got hot and melted through the housing. I cleaned everything up, bent the contact back into the right spot, reassembled, and it fired up. I'll need to replace it sooner than later, but I have no more excuses now.

Today I gave the block a scrub to prepare it for paint and assembly.

 

Glad to see an update. Your Jeep is sick, even cooler now with the M/T swap. My buddy had one in highschool and other than copius amounts of massive oil leaks it was a great truck. We had fun mobbing that thing in the mountains.

Glad to see some progress on the engine. Stoked to follow the build.

 

Happy to see an update on this one. Was actually thinking about you the other day, and it seems we’ve both been dealing with XJ stuff lately. Glad you got her figured out, and Godspeed on finishing the engine.

 

Thanks for the encouragement guys!

Engine work has always intimidated me. The sensitivity to dirt and surface finish just doesn't match my usual style of working - overthink the details, and yet somehow also move my hands too quickly. It's why I've ignored how long the machine shop took, why I've ignored the Miata shaped elephant in my garage, and why I haven't posted anything here in a while. Time to be a big boy and face my... discomfort?

I've not found an all in one comprehensive guide on a fairly factory rebuild of a Miata engine. This won't be that. But since I'll be working slowly, I'll have plenty of time to capture the details and maybe even get some live feedback on if I make a mistake or if I'm on the right track.

Step 1: Cleaning

I cleaned the outside of the engine and gave it a coat of paint.



After painting, I gave it one final wash before before I considered it assembly ready.

Most how-to videos recommend cleaning every surface of the block with dish soap and water. I was afraid I would get some flash rust on the cylinders. So before the wash, I coated the bores with marine bearing grease. These will get deep cleaned with ATF and WD40 before new rings go in.

During the wash, I avoided scrubbing the bores and focused on the block interior and the oil galleys. I went over it three complete times - lather it with soapy water, scrub with brushes, rinse, and immediately get it soapy again to have a minimum of water beading and air contact with the bare metal.

Then I blew it off with a leaf blower for bulk water removal, a quick once over with compressed air, and immediately hosed down every bit of bare metal with WD40. I went back and forth between WD40, brake clean, paper towels, and compressed air to get every bit of flash corrosion I could out of the block. I pat dried it with paper towels before one final spray with compressed air. Another benefit of the block casting surface clean I did before the machine shop is that I had much less issue with any towels tearing and leaving lint.

The results look great! A few spots of paint will need a bit of touch up due to brake clean. I had tried to avoid using it so close to fresh paint, but I failed. Worth it.





To clean the oil passages on the crank, I bent a little red spray tube and stuck it into the blind ends of the crank drillings. I was impressed by how much gunk came out. I used 3 cans of brake clean fluid, and kept going until I felt I was being wasteful with only clean liquid coming out. This necessitated a lot of trips outside to dump the drain pan. I took my time and would spray in the cleaner and let it sit for a few minutes. Just like when cleaning the block, I finished by alternating between WD40, brake clean, and compressed air. It seemed to help get that last bit of crud out on the block.





I've also gone through and cleaned up the parts I'll be reusing. Things like the main cap bolts, oil squirters and their bolts, rear main seal older, etc etc so that assembly is as smooth as possible. Everything is cleaned, lightly oiled with WD40, and bagged to keep dust off.

Next up will be measuring the ring end gap and assembling the rods/pistons. I'll be plastigauging the main and rod bearings as well, but that will happen during assembly. I left the pistons at the shop during the work and only ordered bearings after getting feedback on the crank diameter, so I'm not expecting to have to file rings or change bearings.

 

Whoa, that's more gunk than I'd expect to be in the crank passages. I went hard on my BP build with brake clean when I assembled it, but definitely not as hard as you. I wonder how much crap ended up going through my bearings

Glad to see you're back on the horse with the project. I wondered where you were for a while, but figured you had a bunch of other projects going on aside from the Miata.

Man-swapped XJ looks sick and I'm stoked to see you get the motor together!

 

Oh wow! Love the commitment in getting it squeaky clean!

 

Thankfully all that gunk was basically just carbon, as you'd expect. There was no structure to it, or metallic shavings.

Unfortunately, I took off my safety glasses at one point while cleaning the block and instead relied on my safety squints. Something got in my eye while using compressed air and it got really bad, I was basically bedridden on Saturday. I'm pretty much fine now, but it's worth remembering to not be as dumb as me and wear your safety gear.

I checked the ring gaps and ran into an issue right from the start. I assumed buying Mazda parts meant they'd be pre-gapped. That doesn't seem to be the case. I only checked one set of rings on one cylinder - the top ring was on the tight side of spec, and the second ring was too tight. Guess I need to order a ring filing tool.

 

Obviously there's been a long delay. I spent the Christmas holidays in Canada, took a ski trip to Austria, and on that trip caught something that's had me sick for over two weeks. I've never been sick this long, not even from COVID. Other people on the trip also caught it and no one has tested positive for the flu or COVID, so I have no idea what we got. Plus the recent ice storm... just so many delays.

I started assembly two nights ago. I used plastigauge to confirm the machine shops measurements. He told me even after the crank polish, standard size bearings were all I needed. Every main bearing measured out to 0.020" of clearance. On the loose side according to the FSM which asks for 0.018" as a maximum, but right in the middle of Flyin' Miata's reccomendation of 0.015" - 0.025" for aftermarket bearings.



All of them came out identical.



I got the piston oil squirters installed (torqued dry, no loctite) and the crankshaft in. Everything spins smooth and free.



Last night, I went to double check the piston rings as it seemed to me the machinist hadn't taken very long at all to get it done while I was in the shop waiting. Previously, I had taken the block back home while he waited on one last part to finish the head, and found the rings needed to be filed. Contrary to all the online advice I read, out of the box I found the second ring on the first cylinder I measured was tighter than the 1st ring and stopped there. The machinist said he would gap them for me free of charge, so I took the block back and told him my concerns about the first vs second ring gap. He went back into the shop and 30 minutes later came out with the rings bagged by cylinder. I paid the total bill for everything, brought it home, and went on a ski trip.

On first inspection prior to assembly, the rings he filed had burrs on the lower/upper edge even though he said he had deburred it. Maybe he meant just the cylinder wall facing side. The filed edge was also slightly rounded. He'd done this by hand, not with one of the dedicated ring filing machines that I figured he'd use and is shown in every online video. Great. I filed off the burrs and got to measuring.

I printed out this tool to get the rings down into the bore. I wasn't happy with using the domed piston since it only contacts the rings on the ends of the dome peak, and not the edge of the piston itself. I settled on 12mm depth to measure at.



Below are the FSM specs from a manual I got off of Mellens.



And here's what I measured, after the machinist filed them.



Again, every online video I can find recommends a larger 2nd ring gap than the first ring, and I specifically told him that's why I came back to him. And here I am, still needing to file my rings if that advice is to be believed.

I'll never try to do a high quality rebuild of another engine unless I can get a long list of extremely happy customers and a quick turnaround time from the same shop. I'm so tired of not having my car. At this point I wish I had just bought a primo rebuild from a local Spec Miata guru, Rossini Racing. He quoted me basically $5k and it would have been worth it if I had gotten a high quality rebuilt engine in my car months ago. Or I could have just kept that bullshit JDM engine. I have no idea how other people get work done so fast, and I don't even have a wife or kids. Obviously, I'm not thrilled with my machine shop experience either.

 

When I rebuilt my engine I had a similar experience with the machine shop. Most of the reviews about the shop said they wouldn't really get your work done unless you called in. I tried not to be obnoxious, but I made a few calls to check on progress and such. I think it's just the nature of the game. They also did a pretty poor job cleaning up the head IMO, but they were available and one of the cheaper options. The engine's still running, so I guess they did a good enough job.

Now I'm going to have to build another engine just to delve into the world of 3d printed engine building tools. I found a good number of seal install tools (Rear main, cam, timing gear locker, etc...) previously, but that ring tool is pretty neat and probably would've saved me from dropping my piston on the ground

I feel ya on not having the car. I get anxious every time my car goes down for a major service. It's usually an obsession of mine to get things put back together ASAP which isn't always the best when you're trying to do things properly. Nothing like heading into the garage to make some progress and realizing you need to order a special bolt.

 

The first estimate I got from him back in July was less than a month turnaround, and that's the reason I went down this path. He'd done small jobs for me before on a quick turnaround, spoke clearly and competently with a lot of knowledge on a lot of different engines, and I saw different cylinder heads going in and out of the shop fairly often, so I assumed he got everything done fast. I checked in regularly, I even went back with a request to just have him bore the block and polish the crank and that I'd get an off the shelf reman cylinder head if that was the holdup. I talked to some other local car guys about any shops they would recommend that I could get my stuff back and change machinists, and was told that this is pretty much par for the course.

I'll do a quick and dirty rebuild of something like my Jeep engine, sure. I might even consider getting engine work done at a shop, if it's a spare block. But I definitely won't expect to ever get an engine rebuilt to a high standard in a timely fashion.

The problem is that I'm seemingly the only person I can trust to put in the effort to get a quality result, and like most people, I just don't have the tools to do most engine machine shop work. But at least I can file my own rings.

 

Yup, I think I was also quoted about a month, but I think that was pretty close to the actual turnaround time. I chose to have the machine shop do as little as possible because I didn't want to pay for it or wait for it, and I wanted to learn. Definitely helps having friends who will loan micrometers, ring filing tools, compressors, etc...

I think it's probably like babies at a hospital, to you, yours is the most special in the world, to the nurses, it's just another baby. They're hopefully going to treat it with care, but it isn't nearly as special to them as it is to you, but you know ...with engines.

 

Damn dude, that's a pain. All of it, including getting sick for two weeks. I'm sure whatever you got in Austria is different than what's been going around here, but a ton of people I know have been catching a similar bug that kicks your *** for two weeks then leaves a lingering cough for even longer. Sh*tty. I assume the ski trip was kick *** though, yeah?

That's annoying about the piston rings, second gap should be larger for sure, or at the very least not tighter than the top gap. FWIW, I filed the rings in my current engine by hand and ended up slightly rounding a couple of the edges. No issues after quite a bit of abuse so far.

Can confirm along with Sim that timeframe/needing to check up multiple times sounds par for the course too re: most machine shops. The machine shop I've always gone to has never done me wrong, but all they do when you come in is write your name and phone number on a sheet of yellow notebook paper and put it god knows where. I've always had to call them and have either gotten a "Oh yeah, your block's been done for a week." or "Ahh yeah, the guy with the cams that need polishing. Yeah, we'll do 'em tomorrow."

That kind of service seems like the going rate to some extent. It seems like every shop I've ever called is swimming in work and can afford to just... not follow up or give solid ETA's. Good for them I guess.

3D printed ring setting tool is kick ***. I need to get a dedicated tool like that. Using a piston itself is cumbersome.

 

Thanks for commiserating on the machine shops guys. It still sucks, but at least I feel like I'm not the only one getting the run around.

Oh hell yeah! I've done a few trips out west - several to Vail and Breckenridge (including taking a day off on a work trip, hehe), Snowbird, and Whistler. Honestly I'm probably going to make future big trips out of the US. I'm sure it's different for you guys out west in driving distance of great slopes, but flying into a pricey Epic or Ikon resort and paying most of $1k for a week of lift tickets pretty much offsets the higher flight costs of going to Europe. Sure, there weren't glades like Snowbird, but Arlberg was a massive resort. I think the group I go with is going to keep looking to Europe or maybe even Japan. I'd like to try somewhere in South America once, just to get a complete change of pace.

I just missed a great dumping of snow, but it made for decent conditions the rest of the week. On the last day it was seriously starting to melt, so we lucked out for being there early in the season. There was no snow coming for at least a week after we left.





I poo poo'd on them before, but 3d printers and filaments have gotten so good that IMO it's fast becoming an essential tool for DIY types of mechanics. I whipped up the design for that in 5 minutes and printed it in 27. I went to get a ring compressor while it worked.

Friday night a buddy that's done it before came over to help me re-gap the piston rings. We opened up the top ring to 0.017", and the second ring to 0.022" using hand files. Having another set of hands really helped keep the file steady and the filed edge pretty square. I got the pistons installed and rings on there...



... Before I had a moment of stupidity. The lack of alignment between the rod bearings and the rod cap gave me the heebie jeebies.



With yet another massive snowstorm coming, I spent the weekend dealing with other responsibilities. I came back with a clear mind, tested out the old bearings, and remembered that plain bearings have a crush spec. Time to slap those pistons in. All of the rods came out to having 0.020" clearance according to the plastigauge.



They're all installed and ready to go.





1.9L BIG BLOCK POWERRRRR.

Hopefully assembly will be smooth sailing from here with no more measuring. The only real fun I expect will be packing the oil pump gears and sealing up the oil pan.

 

Haha so FWIW, I'm not a snow guy myself, I just spend a lot of time at our mountain resorts in the summer playing around on the mountain bike. Funny you'd mention Europe/Japan, though. I've got a bunch of buddies who are hardcore snow guys and do a lot of trips to Mammoth, Utah, Tahoe, etc. A group of them are in Japan right now and have been saying it's the best snow they've ever boarded in.

Your pics look epic haha.

Can't wait to see the BP rippin' again!

 

I like Winter Park in Colorado. Skied in Germany and Austria a bit but preferred WP to everywhere I went. Copper Mountain was good, too.

 

Slow and steady progress is the theme. Being my first engine build, everything is getting double checked and I'm researching every step along the way. Heck, before bolting down the oil pan I triple checked the torque on the rods, main caps, and oil squirters even though I had written down that I'd already double checked them after install.

I hope that posting some of the lessons I learn will help someone else. That's probably not likely since this is a build thread in 2026 and not a standalone engine related thread. Whatever. I like writing stuff down.

Oil galley plugs and the restrictor to the head are installed. I did this after installing the crankshaft based on watching Greg Peter's video, and I wish I had done it before installing any other parts. See the tiny bits of brass that were shaved off by the block? While I'm confident none went forward and into the oil galley, I'd rather have had the chance to flush the oil galley one last time with brake clean and air.



I'm using a new factory oil pump. I've heard too many QC issues with Boundary Engineering pumps to think that it's an upgrade at my power level.

I didn't open the pump up to pack the gears either. I just squirted in some assembly lube and rotated the pump until it was smooth and took some effort to turn. Call it packed.



One last look at the DCBE trap door style oil pan baffle.



I topped it with a Sagespeed flat baffle. The new longer bolts got blue loctite. The washers on the front two to hopefully prevent any long term harmonic issues with the longer, less well supported front portion of the baffle.



Another line of Permatex Grey. I aimed for the factory spec of ~3mm bead, and put an extra line on the seams between the block, oil pump, and RMS housing.

If you squint, at two corners of the block you can see I cut down some long M6x1 bolts to serve as alignment studs for the MBSP and oil pan. The hope was to minimize smearing of the RTV.



No pictures of every layer, of the install, but I finished off by wiping the excess away once the pan was bolted down. Nice and tidy!



To install the oil filter stud, I used a double nut method. Since I don't have spare engines sitting around, I cut up an old oil filter to serve as the second nut. I couldn't find as much information as I would have liked on how people choose to do this, but I installed it dry, no loctite.



I found this video from JPM Performance, a Spec Miata shop, to be the best visual guide for the oil pan install process.


The best bit of advice in it is to buy this little tool for dispensing RTV. It works fantastic, I paid like $20, it's made in USA, and the knockoffs are maybe $2 cheaper. (Not my picture, not my hand)



There is not much left from here other than bolting on the head, but I'm probably going to spend a bit of extra time looking it over after the questions I've had about the machine shop. The finicky part is almost over!

And then I've got to remember how all of the rest of the car goes back together.

 

Let's check valve lash before installing the head.






I brought the head upstairs out of my basement hoping that being at 70* instead of 50* might bring some of these back into spec. I am not going to look up the rates of expansion of aluminum and steel. I am just going to blindly hope.

The machine shop adjusted valve lash by grinding the valve tips. Any chance this could result in a small amount of break in loosening the clearances?

 

Fruitless effort to check without it bolted to the block. Do that first, then check and adjust.

 

Well seeing as I didn't bring him any head bolts, I'm confident he didn't bolt down the head to do the lash adjustment at the shop, so I'm checking them the same way he would have. During teardown I did measure before removing the head, but that's sort of a moot point now. It's just frustrating to find more (likely) issues with the work I waited 6 months on.

Any other checks I should do with the head off before crushing a head gasket? I can at least confirm he did do a valve job, and appears to have checked for sealing. And painted the whole cylinder head silver, which I am not a fan of. Somehow I doubt he masked off the cam bores.

 

That’s all typical of a head shop. You can spray soapy water on an upside down head and shoot compressed air in the ports to check for leaks. The difference between .006 and .007 is going to be down to feel and tooling, I wouldn’t worry about it. I’m typically ok going .001 above and below the spec.