Chiming in for another datapoint, my car's current engine that I put together has a .002" max variance in lash on both the intake and exhaust cams. No issues after maybe 5k miles and ten track days.

Not sure if this is worth bringing up but all the performance cam companies for the MZR/Duratec also recommend running .002-.003" tighter lash than the factory spec. Factory spec on the intake cam is .008-.010", exhaust is .011-.013". I targeted .007" on my intake valves and .010" on the exhaust, although one of my intakes wound up at .006" and one of my exhausts is .008". Not saying the same applies to a BP, but maybe that's worth a little peace of mind if you wind up just slightly tight.

But yeah, what Curly said. Not worth making the call without bolting down the head first.

 

Thanks for the reassurance guys. I love being able to tap into more experienced minds!

Warming up the head definitely improved the situation. One is still definitely 0.006, but the other three have improved to a tight 0.007. Let's see what things go to after it gets bolted down.

 

Got some work in over the weekend.

I took the head back downstairs and let it chill. The valve clearances tightened back up, so I'm not just bad at measuring. Maybe the basement garage is colder than I thought.

I'm finally doing a reroute on this engine, so I used a regular 94-00 head gasket.



Is that an extended oil filter? Or are you just happy to see me?

After installing the head, I checked the valve clearances for a third time. All but the last two valves (intake and exhaust) were the same as when the head was off. Those two got looser.

The whole experience has me rethinking how good of a band aid the 01-05 gasket is for the coolant routing. The cylinder 4 valves were the tightest prior to the rebuild. After getting the head skimmed, the only valves that changed clearance after being bolted down were the furthest rear two. On the other hand, it did get to 195k miles and a simple valve adjustment at any point in my 70k miles of ownership and tracking could have prevented my misfire. That might have been enough for me to never go looking for cylinder bore damage.

On with the rest of the assembly. A year or two ago I picked up one of the cast impeller water pumps because they were the hot stuff and the rumor was NAPA was running out of stock. Since then the hype has cooled down somewhat. I don't think this is that much of an upgrade because the impeller has such a terrible surface finish, but some people still seek them out.



Another silly mod. For some reason, the mixing manifold has a round outlet, and the water pump has a rectangular inlet. It's a known quirk that has zero real world consequences and no one blames it for causing any issues.



I took a die grinder to both to make them a better match. Ta da. Time wasted just to give me the warm fuzzies.



More went on, and I broke out my handy universal pin wrench crank holder combination tool. I'm being a little bit extra with the bolt torque markings. Peep the orange, finally got some on my car.



That let me torque down the clutch and flywheel.

I put the reroute on Friday night and the coolant gasket RTV is STILL tacky. Another sign the garage is colder than I realize.



Am I crazy for kind of wanting to leave the valve cover as is for now? If all goes well and my rebuild results in a nice running engine, it will have earned a new coat of paint on its little hat.

Back in the summer I designed a block off plate for the water neck hole.



For some reason, in all the intervening months I did nothing to prepare the other components to go back on the car. 195k miles of goo was fun to scrape off of the transmission and out of the intake manifold. I'll be re-installing the 5 speed rather than the JDM 6 speed so I can focus on breaking in the engine.

New rule for caked on oil goo - Spray it with WD40 or some other cheap light oil before washing with engine degreaser. It all comes off so much easier with an oil based solvent softening it up first.



Last Wednesday I realized I still needed to order some seals and torx screws for the VVT mechanism. I paid extra for UPS shipping, and soon got an estimate that they would make it to me in a week - this coming Wednesday. That was lame, but maybe they were just being conservative? I was surprised that within 36 hours of placing the order, they were in my town. Since then, UPS has decided that they needed to wait 3 days in the warehouse before they would put them on a delivery truck, just to make it a bit closer to their estimate.

Screw you, UPS. Next time I'm using some other service until they upset me enough that I have to come crawling back.




It can be done in car at least, so I can keep moving ahead. But I was hoping these parts would arrive sooner and I could get it all done on the stand.

It's not a big deal though. Right now the goal is to have the car ready to drive Saturday morning so I can do the test drive and ring seating in daylight hours. Plenty of time for me to find more silly side adventures.

 

I've been doing a lot of detail stuff to prepare the engine for install.

I was looking up some other info when I came across some complaints about the QMAX having a large coolant bypass and not coming up to temp. Since I still have the heater and the oil cooler, there's no need for a thermostat bypass to avoid deadheading the water pump. So I decided to take that apart. Even though it seems like this bleed hole has been reduced in size from earlier versions of the QMAX, I went ahead and sealed it shut with some silicone and used enough to prevent leaks all around the thermostat. The stock thermostat housing is almost perfectly sealed with the thermostat cold. This isn't any different from a stock system in a FWD Mazda B engine.

Overall, I'm quite happy with it. It's a well thought out piece at a good price. I had to massage the EGR pipe to get it to not rest on the housing, but apparently there is a lot of variation in the pipes.



To clean up the front of the engine, I made a custom formed hose to go from the oil cooler straight to the mixing manifold routed behind the timing belt cover. Normally the coolant would go from the cooler, to the throttle body, to the thermostat housing, and finally to the mixing manifold. With a S2 throttle body and a deleted water neck, the stock hoses are just overcomplicated. This is much simpler and more elegant. It's 3/8" the whole way, whereas the stock unit is 5/16 until the thermostat neck, and then 3/8 to the mixing manifold. Maybe I'll get an infinitesimally small improvement in the oil cooler performance with it not having to share a flowpath with coolant right from the thermostat.

I test fit the hose, marked the bend locations, pushed in a thick copper wire to make the hose hold it's shape, bent that and zip tied it in place, then baked it in the oven at 350 for 45 minutes. It holds shape pretty good!



This is the test fit. Nothing is holding the hose in place anymore except for it's new memory.



I had to do a lot of digging through my old pictures, notes, forums, and youtube videos to get everything back in it's right spot. But it's just about there.





I'd like to get it installed Sunday, preferably. When I set my Saturday goal earlier this week, I forgot what day that was...

 

Interesting bit re: the coolant reroute allowing substantial bleed-by when closed. I always suspected something like that was happening as my NA didn't like to get up to temp when it was cold out, and would drop below thermostat temp pretty quick while coasting downhill. Surprised I never saw any other talk of this until now.

Also how am I just learning about forming hoses in the oven? That's brilliant, I've got at least four generic hoses on my car that could use that treatment haha.

 

It's a great trick. I'm not sure how it would work with the larger radiator hoses, but for these little ones it seems to work great.

For the reroute, I understand why the bypass is there for a racecar with only two radiator hoses, but for a street car with substantial coolant flow bypass through the heater core it's just not necessary.

Anyways, I met my target timeline for once. Installing the engine solo, with the small 1 ton HF cherry picker, a coolant reroute, and VVT motor mounts was a uniquely miserable game of Tetris. I didn't have enough reach with the hoist and balance bar at a neutral setting, so I was going back and forth between the balance bar, a floor jack, removing the engine mounts, and trying to wiggle them back into place for probably two hours.

Next time I'll change something. A larger engine crane, earlier mounts, install the reroute after the engine is in... something.



I pre-filled the massive 1347 filter. with the VVT oil feed left loose, I had oil leaking out in about 10 seconds of cranking. With that sealed it's building great pressure. My plan is to get all the last details sorted tonight, and drive tomorrow.

 

Looks great! I think the bypass hole is to prevent CLT yo-yoing which can be annoying and kick the car in/out of warmup mode. Just something to keep an eye on. Glad to see this thing coming together!!!

 

Same!

I've got several "Frankenstein hoses" (made from other hoses with the required bends/angles and hose joiners) that could be replaced with this technique,

Possibly an excuse to get a larger kitchen oven for those long hoses?

Pos-cat added.

 

Live view of my hands and arms.



This damn car scraped a lot of skin off over the past few days. I'm tired of grabbing dinky tiny parts buried behind the sharp edges of all the different evap and AC brackets and new reroute hose to reach that oil filter or those motor mounts.

But I drove it to work today.

Yesterday I followed-ish the FM new engine break in procedure. I used Lucas straight 30 weight break in oil and the massive Wix 51347 filter, got it started, reinstalled the plug wire that I knocked loose that was causing a miss, drove it 3 miles to a country road to warm it up, and did repeated 2,500 - 6,000 RPM WOT pulls and coasts down. FM says to do this five times. I did it... well, a lot more than that for an 8 mile loop. I drove it back home, changed the 14 mile old oil for another round of 30 weight break in oil, cursed myself for putting the first filter on too tight when the engine was on a stand, replaced it with another 51347 filter, and took the car out for another 40 mile drive of mixed throttle and RPM.

When I got home I checked over the oil that had drained out more closely. The first oil change was of course, sparkly. I didn't see any significant large chunks of metal. The second oil change was much cleaner as you'd expect.

I cut open the two filters to have a look. Can you guess which one was the first run?



Here's what I found in the bottom of the second oil change. Most of the flakes in the oil looked to be dried paint in green and white shades. I'm guessing this is paint that fell off of the valve springs, but I don't recall how they were marked. There were a few flakes of metal here and there in the first batch of oil, but they always look bigger than they feel. I'm not worried about it.



The honda filter vs the filter she tells you not to worry about.



I did a second oil change in one night with Supertech conventional 10W40 and a Honda filter. I'm debating if I should change this in 250-500 miles, or just go to the usual 1k break in miles everyone recommends before switching to synthetic.

I'd rather have a bit of hysteresis around the proper temperature than have it take forever to get up to temp and not bounce. IMO the logic of the reroute has always been to put it back to how Mazda originally designed the BP, and they didn't have any significant thermostat bypass to the radiator. I'm glad I sealed it up. But that's my opinion and it's worth what you paid for it!

I didn't see any bad behavior on coolant temps. Once it got above 185 it stayed there, generally right around 190. It did wander a bit more than I remember, but that could be down to air bubbles getting bled out and the new coolant path and sensor position. I've also been spending a lot of time recently monitoring my XJs coolant temps, and I never really did that with the Miata, so my memory is probably skewed.

Anyways. Time to see when the next track day is on MotorsportReg.

 

Congrats!! So satisfying to break in a fresh motor. Though the OCD of checking oil filters I could do without (and I did without on my last motor rebuild, because it drives my automotive paranoia through the roof). If it dies, it dies, I said. 25k miles later it hasn't died yet! Good on you for doing the right thing though.

I'd normally agree, but after experiencing massive overcooling, and yo-yoing on my very well ducted/overcooled setup on a 70* day in the canyons, I'll stick with a car that stays in warmup mode longer than one that goes in and out of operating temp like that. I think it's setup dependent though, and my thermostat location wasn't helping either. So you'll be fine. The Qmax reroute is fantastic compared to the oldskool DIY stuff I was using before, 10/10!

Keep us posted on the break in!

 

WTF WHEN DID EVERY TRACK DAY BECOME $400???





That's why I only looked at the oil and filter after I was done driving for the night. Seeing sparkles without any experience of what's normal would just have me second guessing stuff. Either it was going to work perfectly or it was going to get replaced, so why only fail halfway? Send it.

Strange behavior for sure, glad I had nothing like that.

I gotta say, the massive PITA that a reroute is to deal with makes me kind of wish I'd just gone back to the stock VVT headgasket. The valves on #4 were the tightest and it was the only cylinder that had any real change in valve clearance when bolted down (making me think it was very slightly warped there). That said, the stock design clearly worked okay for 195k miles. No shade to Supermiata, the part itself is a great design and high quality. It's just the nature of sticking parts where Mazda never intended to have anything. But the hard part is done now and I have an extremely effective cooling system for the massive 1861cc block of bigs.

 

Heck yeah dude, good sh*t! Didn't expect to see this post so soon.

I'm also now in Fire's camp regarding tearing filters open. I went through a phase when I built my BP of checking the filters and freaking out at any material found in there, without knowing what was normal. I even grabbed a bunch of used filters from work and cut them all open to compare at one point lol. Sounds like you're in a good position right now. Can't wait to hear how it holds up at the track!

 

We can't all be as quick of a wrench turner as you! These past few weeks have been humbling.

But I am going to have to start studying your ways at the track. I need to get enough time trial experience under my belt to become an instructor and get those discounted track days. Costs have gone up a lottt in the past few years.

 

None of us are as fast as he is!

It's not just you, if that is any consolation - what was a $250 entry is now $350 here, $400 if you miss the early-bird price

 

Do you ever run with NASA Southeast? Different NASA regions handle things differently but they all generally work the same. In our region, you have to move up through run groups (they're more focused on safety and passing/traffic competence than outright speed) until you're in HPDE4 (the advanced group), then pass your TT license test, then you can take your instructor license test. These are guidelines, though, and they're a little flexible with the process depending on your previous track experience. Truth be told, I got my instructor license kinda by accident/default. Our region was super short on instructors at the end of 2024, so they recruited any willing TT racers to stand in as first time instructors for the final two events of the season. After two events of positive feedback, I got my license without having to test for it.

Having event costs covered and the Hawk/Summit contingencies you get from every few days of instructing are a huge help. Only drawback is that you've got less free time in the paddock if your car has some sort of critical failure early in the day lol.

Message me if you're interested, I'd be glad to run you through the process. The NASA website isn't a huge help, but the process to becoming an instructor with them is pretty straightforward.
//Threadjack, sorry

 

Another friend also recommended running with NASA, so I think I'll start with them. The whole ethos of this car is unending seat time and durability at the track (and getting there somewhat comfortably), so losing spare time in the paddock isn't a concern for me. Knock on wood, I haven't had a day ending issue since I ripped out the megasquirt.

By their own guidelines I should be able to get into HPDE4 pretty quickly, I have documentation for 25 track days, but probably have done significantly more with walk up registrations and private run groups. And being a decently competent Miata driver, I'm familiar with giving point bys quickly, and how frustrating it is to not get one!

PM incoming.

 

Great to see the progress and that things are going well brother! For what's worth, I haven't had a day ending issue related to LinkECU . You know you've got some ponies hiding somewhere in a tune.

I also never had a serious issue with Megasquirt either, but that doesn't push buttons the same way.

 

I won't lie, the Beer Money Motorsports unit has been tempting me. Onboard wideband support so no CAN link or 0-5v analog output along with an $825 buy in is awfully well priced. That would inevitably lead to EGR delete, evap simplification, flat top intake and getting rid of that awful VTCS during warm up... Oh man. It's best not to think about it.

If I'd have bought a new ECU back in 2018 instead of the used one I got with hackjob wiring, I'd probably not have had any issues and the path I took this car could have been very different if that MP62 supercharger I had ever got installed. That was 8 years ago though.

Last night I just realized I've owned this car for 10 years. It's absurd how much work goes into keeping a car looking basically stock.

 

I've finally crossed 1,000 miles since the rebuild! The oil still looks clean and is at pretty much at the same spot on the dipstick, so I don't seem to be burning or leaking any significant amount of oil. I'll be honest, I was hoping to feel a bigger power bump after the rebuild, but I got exactly what I said I wanted - a stock rebuilt engine, ready for loads more miles and track days. No complaints!

Yesterday I took it into the NC mountains to stretch its legs and remember how to drive. It's been a long time since I enjoyed driving on public roads that much. Like a lot of people say, once you have some seat time actually pushing to your limits on track, driving much past 7/10s on the street doesn't feel safe or right. But there's still a lot of fun in seeing how close you can ride that edge of propriety and your sightline. You focus on keeping it smooth, not just on speed.

No pictures because I didn't come across any overlooks, and to be honest, the Appalachians in early spring aren't that photogenic. Oh look... reddish brown buds on leafless trees. But this is the sort of random little road you can go down that will never be marked on a list of great driving roads.



Since I was having too good of a time, the Gods saw fit to bring me back down to earth. I'm getting close to needing new tires, but I'll plug this one for now.



No matter how much I adjusted and tinkered with multiple sets of top latches, I could never get them to get tight enough. I got tired of squeaks and wind noise so I sprung for some of the cheap ~$80 latches that are all over eBay and Amazon. Sometimes it's nice to just hit the easy button. They work well, but I'm still right at the tight end of adjustment with no room to tighten them further, so I am not sure how long I'll be happy with the situation.



I've been having fun with the 3d printer too.

The GM hose is a great fit for the reoute, but it was rubbing on the AC lines and throttle body cam. So I whipped up some supports.

This front support will probably be redesigned at some point to actually bolt down. For now, it just wedges into place and hangs off of the evap canister. The red is just a test print in PLA, I reprinted in black ABS.



I made this one that shares bolt holes with a vacuum solenoid hanging off of the VTCS manifold.



At the back of the engine, this holds the hose off the AC hardlines.



I also took the time to revisit my prop valve mount. The previous solution was... unprofessional.




The 3d printed parts haven't all been great though. The water neck delete plate I designed based off of stock dimensions ended up moving around and getting eaten by the water pump pulley. I'll have to cut off the rubber that's bonded to the timing cover and make it a tighter fit.



I've got some other projects brewing too. I have mixed feelings on the DIY poly/bronze setup. The alloy we used for the center sleeves is rusting, as I posted about previously. I hadn't been picky because I figured it wouldn't have an issue, being covered in grease and all. That wasn't the case. I'm also getting the FLCA-F failure that's so common, although it hasn't been catastrophic yet.

So, why not spring for some upgrades? In the rear I've got my eye on a bushing that's proven to work at an OEM level, and a few Miatas are running these successfully in the rear suspension. It's a sealed ball joint/spherical bearing common in 90's Mercedes sedans. A bit of digging in the Moog catalog shows these style of bushings are actually pretty common across different manufacturers, but I'll stick with this one that is known to work and fits well in the 40mm ID Miata control arms. In the front there have been some failures from braking loads, so I'll have to revisit the Delrin solution I was working on. Really all I need is a reamer to true up the bushing after it's pressed in.

These are obviously just test prints. I'll get the sleeves machined out of 17-4 stainless for strength and corrosion resistance.



I'm also celebrating 10 years of owning an uninstalled SADFab RUCA-O spherical bearing kit. With TPU filaments now allowing you to make your own seals that are a tight fit, I am again interested in running these.



Never content to leave well enough alone, I also want easier camber adjustments with a larger range. On my last alignment for winter street duty, I couldn't get less than -2.0 degrees of camber in the back. Plus juggling camber, toe, and thrust angle with only two adjusters makes DIY alignments more of a pain than they need to be.

I've designed some eccentric fences that will be CNC'd and welded in to the stock RUCA. AWR will sell you the same basic thing for $300, or if you want something stiffer, V8R also has a tubular RUCA. My buddy recreated the SADFab bearing spacers, but in stainless steel, a 12mm ID to use another alignment eccentric, and a wider diameter to spread the clamp load.



I probably should focus on getting a track alignment back on the car though! It's time to really let the engine sing.

 

Damn, you've been busy! Congrats on the 1k mile mark. Still looking forward to hearing the first post-trackday report.