K-swap How-to: A by-the-book K24A2 NB2 swap build thread
 

I have been trying to get my hands on a K-swap project for about 18 months now. The combination of Miata chassis dynamics and N/A K24 power is too cool to not love, even for a boostaholic like me. I've had too much going on to buy a chassis and build one myself, but I was able to convince a good friend of mine to do it instead.

Emilio did a good job of documenting his buildup, but he went well off the beaten path. Cool build from a technical standpoint but minimal relevance to anyone trying to actuall build a car for themselves. This build will be a bit more conventional and relevant. Kmiata swap kit, 2006 K24A2 longblock, off-the-shelf intake/exhaust parts, built mostly as a daily driver. The donor is a clean 130k mile NB2 Sport car, so the 6-speed and Sport brakes are already in place.

Poor thing will never know what hit it.

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David from K-Miata and John from Inertialab are out this weekend assisting with the buildup. David will be cutting an instructional video that goes into more detail, but this thread should be a good resource for customers who are looking for some help or potential customers who want to understand what they're getting into.

The donor car is a 2002 Sport package car without ABS. The 01-02s are the sweet spot for the NBs, since you get all the benefits of the NB2 (nicer interior) without having to deal with the T-F diffs. In addition to the K24, the car will get 700/400 Gen2 XIDAs, a Blackbird Fabworx bar, 15x9 6ULs, and a bunch of other upgrades to support the new powerplant. More on the extra upgrades once the engine is in the car.

First step is pretty straightforward - drop all the stock stuff out. We dropped the engine, trans, front subframe, and all the suspension together.

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In addition to the complete engine/trans/subframe removal, you’ll also need to remove your dashboard and HVAC components in order to install the Honda wiring harness and connect it up to the Miata dash harness.

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I’ll have another post or two tonight detailing the engine preparations and the swap kit parts (mounts,subframe, adapter, flywheel, etc).

Good to see this on here, i have seen David posting stuff on social media. Your not gonna want to play with Miata motors any more.

Nice. Will be following.

I'm going to let the cat out of the bag. (No animal abuse to feline on sensitive to cats Miata forum...simply acronym.). I'm going the K swap route.
2 things are going to happen to the future of this forum:
1) people are going to run Honda motors and enjoy their cars.
2) people are going to get amazing deals on part outs from members ditching their turbo setups to go K swap.

Either way, miatas for the win!

Yeah I'm in denial at this point. With Dave and Kmiata being so close to home for me it's becoming a no brainer. I've been building up parts for an N/A build now and to go turbo again down the road but theres a small part of me in the back of my head that keeps screaming "WHY ARE YOU BOTHERING JUST SELL ALL OF IT AND K SWAP"

Yeah, you've said lots of things and done nothing.
Move along and don't clutter up his thread.

One of the things we were able to do was take an extremely accurate weight of the K24 vs the factory engine, including all the auxiliary components that are included with the swap (subframe, flywheel, header, etc). I'm curious to see what you guys think the weight difference is before I say, though. Thoughts?

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15 pounds heavier.

15lbs lighter. Subframe has gotta be a net saver, maybe the K24 block too.

22 pounds lighter Bob

i remember readying in their thread that it saved 50lbs, but who knows how accurate that is.

Awesome thread. 32 pounds lighter WAG.

I'm betting the engine itself is 35-40 lbs lighter, the subframe is probably 10lbs lighter than the stock one. I'm betting the rest of it is a wash.

The kicker will be how it was weighed. The k swap can not run a/c or p/s. So was the the BP weighed with the accessories?

How much of a pain in the nuts was it to pull the dash out and do the wiring?

-35lbs, all in. BTW, I know you have SWAG Andrew so I think you need to kick down at least a cool Trackspeed sticker for the right answer. :)

@asmasm is gonna bust a nut if you properly weigh it all and document.

If you are swapping a NB the wiring is very straight forward and not to difficult, NA is another story.

This is very true. There is so much bad information on engine swap weights because accessories can weigh 80+lb and people don't specify what is on the engines when they weigh them. Andrew, I have an 1100lb hanging scale I can lend you if you want something easy to weigh with. I think engines weights for swaps should get compared without clutch/flywheel, exhaust, AC, or PS- But everything else.

From all the weights I have read online I pieced together an estimate that the actual weight of a k24 is about 25lb less than a BP when its dressed the same. That is pretty impressive when you consider one engine is .6l larger displacement and makes about double the horsepower with stockish internals.

The k series swaps are pretty damn awesome, I might have even gone with it if it had been more popular when I first started planning for an ls. I'm guessing about 30#, and I can confirm the bad information about engine swap weights. A lot of the guys try to act like adding a v8 to the car doesn't add weight by saying the bp is super heavy. I've heard some pretty wild weights throw around in the v8 community, hell if you'll let them, they might even convince you that the bp used a tungsten block. I just comfort myself by saying a turbo would have added some weight too.

Is the goal for it be ob2 compliant? Would vins match ecu/car? Pass normal inspection?

Agreed that there's lots of bad info. We wanted to get a weight that was representative of what you had to remove from the car, and then another weight with everything that was reinstalled. The weight of the undressed BP longblock and undressed K24A2 longblocks aren't super relevant, for instance, because you need to use a different header, intake manifold, etc. with each engine. IOW, we weighed what we took out, and we weighed what we installed, and that's the difference.

Fully dressed VVT motor with the following items 468lbs:

• Fully dressed longblock including coils, starter, and alternator
• VCTS intake manifold, throttle body, OEM manifold brace
• OEM VVT header and downpipe
• OEM subframe (no control arms)
• OEM clutch+flywheel
• OEM engine wiring harness (complete to ECU plugs)
• OEM 6-speed
• OEM power steering pump

Fully dressed K24A2, prepared for installation 441lbs:

• K24A2 longblock with coils
• K24 starter motor
• K24 alternator
• KMiata front subframe
• KMiata K20 oil pump/pickup/pan
• KMiata adapter plate and flywheel
• ACT HDSS clutch
• OEM Honda engine harness
• KMiata adapter harness
• OEM 6-speed
• Skunk2 Ultra Street intake manifold
• Skunk2 70mm throttle body
• KMiata street header + crossover pipe

It's not a flawless per-pound comparison, but it's pretty damn close. We didn't account for the factory intake/airbox setup since we haven't built the K24 intake yet, for instance, and we accidentally left the OEM PS pump on the old engine. IMO, 20lbs is a good estimate for the final difference. If you start with a car that has A/C and P/S, the weight loss will be close to 70lbs since you're removing those systems at the same time.

The holes in the K24 are bigger, of course it will be lighter ;)

OK, first big content post. This post will cover all the engine prep required to go from an OEM TSX K24A2 to a prepped, ready-to-install longblock.

We are using a K24A2 longblock from a 2006 TSX for this swap. The K24A2s are definitely the most straightforward engines to use for the swap, and the 06-08s also make the most power in factory form. If you want max power, you can put together a K24/K20 hybrid setup, but the small gains aren't going to be worth it for 95% of customers. Keep in mind that some of the prep info here is going to be specific to the K24A2 block and head, so if you're using something else, pay attention.

To adapt the motor into a Miata, we need to remove the factory balance shafts and install the KMiata oil pan and oil pump setup. This will require removing the timing chain cover, valve cover, oil pan, and a few other items. One of the sole weak points in the entire K24 engine is the timing chain tensioner, so we'll be installing a brand new OEM tensioner on this 100k mile longblock. We will also install a 50deg VTC gear from an RSX Type-S, which substantially improves mid-range torque. Using the 06-08 longblock means we can safely use the 50deg gear without any limiters.

The first step is to pull the timing chain cover. Remove the valve cover, then remove all the 10mm bolts around the edges, as well as the VTC solenoid in the center of the cover and the two bolts next to it. This is RTV'd to the front of the engine, so pry lightly to break the seal. Remove the factory tensioner which sits on the lower left-hand side of the timing chain as well as the right-hand chain guide.

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Also remove the upper chain guide. Once it’s gone, remove the OEM chain and set it aside. The tensioner is replaced, but the chain guides and chain will get reused.

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Flip the engine over and remove the factory oil pan. You’ll be left with the factory K24 oil pump, which incorporates the balance shafts. The steering rack needs to occupy this entire space, so the balance shafts (and the oil pump) have to go.

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Here’s the chain which drives the oil pump. It sits behind the OEM chain and has its own tensioner. This tensioner will get reused, but the guide and chain are unique to the K20 pump. The tensioner and guide both need to be removed to get the oil pump off.

Unbolt the factory oil pump and remove it. The chain won’t come off first, so you’ll have to wiggle the gear off the crank at the same time. It’s easy to do, so don’t force anything.

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You will also use a new K20 windage tray to match the new K20 pump. Remove the OEM windage trays:

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This small orifice needs to be removed and plugged in our block. Use a wood screw to give something to grab onto, then pull it out. It’s held in with an o-ring, so it shouldn’t take a huge amount of force.

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Once it’s out, the block will have threads. Simply install a bolt and a crush washer to plug it.

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The K20A2 oil pump will be disassembled and reassembled with a new rear case half to adapt to the KMiata pickup tube and oil pan. The factory case half is on the left, with the KMiata part on the right. It’s a quick swap over, and the pump is ready to install. Notice that the factory doesn't use any sealant between the two halves - we didn't either.

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Remember that the new chain, new pump, and front pulley all have to go on together.

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In addition to the rear case half, KMiata modifies the K20 oil pump to clear the K24 block. You can see the notch in the oil pump body here:

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Install the K20 windage tray, but leave it loose. The pickup tube installs on one of the center mounting holes. Use the extra OEM bolt to fasten the pickup tube to the KMiata pump adapter with an o-ring to seal on the pump adapter.

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At this point, we have the K20 oil pump with KMiata adapter, new oil pickup tube, K20 windage tray, and the oil pump chain/tensioners all reassembled. We can now jump back to the front of the engine to set the timing and install the new tensioner.

The K24 chain makes it extremely easy to set the timing from scratch. There’s a small dot on the cam pulleys and a small mark on the crank pulley. The timing chain has dark-colored links which correspond to the dots on the various pulleys.

Cam pulley dot lines up with the dark chain links:

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On the crank pulley, there’s only one dark link, and the mark lines up in the middle of that link.

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Install the chain guides and tensioners by pinning the tensioner back, then pull the pin and the tensioner will auto-tension the chain. It sets tension by hydraulics, but there’s also a ratchet system to maintain chain tension during engine startup.

Install the crank trigger wheel with “outside” facing the outside (if you didn’t figure that out on your own, you might be in over your head ;))

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At this point, we can Hondabond the oil pan and timing chain cover into place, re-install the VTEC solenoid, and reinstall the valve cover. It’s not a bad idea to check valve lash while you’re reassembling and adjust if necessary. You should have a dressed K24 longblock at this point with a fresh valve lash job, fresh OEM tensioner, modified K20 pump with KMiata pickup tube, and KMiata oil pan.

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Alec is literally beating off to that post right now

Quick pic of the welded pinion as well. Since you have to depower and shave all the hydraulic fittings off the rack to clear the oil pan, we took the time to properly depower the rack, remove the inner seal, grease the rack, and weld the pinion coupler.

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Sav, if your ever looking to do the double key'd mod to the lower timing gear hit me up. I was doing that mod for a lot of drag k series guys.

Thank you for all the detailed weight info Andrew.

Onwards and downwards. We now have a dressed K24A2, prepped for installation. Time to get the rest of the swap parts installed and get the drivetrain installed.

At this point, we can drop the motor and set it down (carefully) on the oil pan. The adapter plate gets bolted to the engine, then the KMiata flywheel gets bolted up, then the ACT clutch+disc. The 6-speed has to be notched to clear the TSX starter as shown:

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You can also install the flywheel cover at this point.

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There are a couple good plans of attack for actually getting the new engine and subframe into the car, but for this build, we’re trying to stay as relevant as possible to the average customer attempting this swap. So even though I have a really nice offset 2-post lift, we decided to slum it with jackstands and a hoist. :party:

When going in from the top, it goes in just like a Miata engine, so we installed the subframe first.

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The engine goes in all as one unit – full longblock and trans together. Leave the engine mounts off for now.

Halfway in. We unbolted the factory brake booster hardline, since it’s not used and it interferes with the valve cover. The K24 is a tall motor, so getting it in between the firewall and the steering rack is a bit of a chore. Not significantly worse than a Miata, but if you aren’t careful, you’ll struggle pretty good with it.

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When installing engines in general, I try to line the shifter turret up with the hole in the chassis. That gives you a good reference for how far back the engine needs to sit. Once you have the shifter centered in the shifter hole on the chassis, and the steering rack is nestled into the oil pan, you can start thinking about motor mounts. The oil filter will have to come off to install the passenger side, and the starter motor makes installing the driver’s side a bit of a chore.

Once those are bolted up, though, you have a K24 in a Miata, which is sort of the point. :party:

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We decided to put the alternator on at this point along with the 4-pulley setup that KMiata makes. There’s no room for a belt tensioner underneath the throttle body, and there’s barely room for the alternator – it has to be shaved down on the top edge to clear the throttle body (some throttle bodies just don’t fit at all – stick to what works). If needed, you can shim the alternator out with washers later on.

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With that, the engine is in the car. You can hook up the PPF, driveshaft, shifter, etc.

Next post will start to cover the wiring, intake manifold and header, fuel system, and other major systems.

Subscribed. Great documentation, Andrew.

https://www.miataturbo.net/attachmen...ine=1462345583

Dont know whos this is but I saw it at Daytona 24 a few months back. Really cool setup.

Andy Hollis- One Lap Miata

Nice job, great write-up! Was there a delay on the build, or in documenting the build? Looking forward to more pics and info!

David used this build to test out a new ECU/harness setup and we're just working out the kinks before fully documenting it. I should have another big update by the weekend. :)

Thanks for the great info, this will definitely help getting me started.

Took a short break to sort out some wiring. David is using this car to prototype the KTuner option mentioned on his website, and it took a little longer than expected to sort out, but everything is all working now. :party: On with the show!

A few housekeeping items. In order to get the motor around the steering rack, you have to fully depower the rack and shave down the hydraulic fittings on the rack itself. While we were there, John at Inertialab gutted/greased the rack and my local pro welder threw a couple of beads around the pinion for a full depower.

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On to the intake side. We are using Skunk2’s new Ultra Street manifold. This manifold is set up for more pedestrian builds, but most importantly, it has a detatchable and reversible plenum which allows the throttle body to fire forward in the Miata engine bay. KMiata makes a throttle body adapter which kills several birds with one stone. When you flip the plenum, you also flip the throttle body upside down, so KTuner’s adapter bracket solves that. The K-series throttle body is fine, but the K-series TPS that’s attached to it is a tremendous piece of shit, so KMiata’s adapter allows you to run a 70mm B-series throttle body and TPS instead. It also includes a port for the K24 MAP sensor, and the KMiata throttle cable bracket attaches to it as well. The cable bracket is set up for an NB throttle cable.

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When using a K20-style manifold like the Skunk2 on a K24A2 head, there’s an open water port that needs to be routed to the thermostat housing. KMiata provided us with a piece from TracTuff which does that job.

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On the back of the head, KMiata makes a K24-specific rear water neck which provides the main water outlet from the head, an extra 1/8” NPT port, an M14x1.5 port for the factory Miata coolant temp sensor, and a port for the heater core feed.

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For the radiator, we’re using Koyo’s new dual-core Hyper V unit.

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We are using KMiata’s Street header, another new product from David. It’s not quite the bag of snakes that the Race header is, but it’s also half the cost and makes great power.

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The K-series is a returnless setup, same as the Miata, so we just rerouted the factory feed line and built a new nylon line to connect from the Miata feed line to the OEM K24A2 rail. I did slide a little heat shielding over the fuel line for safety, since the header is now on this side of the car.

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A DW100 replaces the factory fuel pump in the tank for a little extra capacity without overpowering the OEM 60psi FPR.

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Next post will go over all the wiring. :party:

Let’s talk about wiring.

For the NB, we started by pulling the dashboard and all the HVAC equipment. We then removed the entire OEM engine harness, which unplugs at a big blue connector under the dash. This blue connector provides power and signals to the ECU, and then runs signals from the ECU to the dash and the rest of the car, so every single wire you need to splice into is available at that connector. (ignore the single wire spliced in at the fuel pump connector, we changed that later)

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We’re using an OEM Honda ECU and a new OEM Honda engine harness. The OEM harness we’re using is from a Honda Element. The Element also came with a K24, so things like the crank sensor and knock sensor are wired correctly for a K24 application (the K20 is wired a little differently). The harness actually comes in two parts – one engine harness and one “charge harness”, which includes the plugs for the alternator, starter, and knock sensor. These harnesses are inexpensive enough that it wasn’t worth the hassle of trying to procure them from a junkyard in good, uncut condition – we just bought brand new parts from a Honda dealer.

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The harness has a few large plastic guards, which all need to come off in order to allow the harness to be packed into the Miata engine bay.

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On the other side of the harness, we have the ECU connectors and a larger grey connector that normally attaches to the Element’s dash/body harness. The two ECU connectors go to the ECU, and the grey connector will plug into the KMiata adapter harness.

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Here’s the ECU and patch harness setup. This is a fully tuneable KTuner ECU. The OEM Element harness plugs into connectors A and B, and the KMiata patch harness plugs into connector E and the grey dash/body connector. There are also a few extra wires for constant +12v, switched +12v, fuel pump, and fan control, as well as wires for the tachometer, CEL, and OEM coolant temp gauge. The KMiata patch harness includes a trio of relays for main relay function, oxygen sensor wideband function, and a fuel pump relay to trigger the OEM 1.6L Miata relay. For this NB application, we bypassed the KMiata fuel pump relay and ran the ECU’s fuel pump output directly to the OEM Miata relay. Everything will get mounted behind the glovebox and tied up/tucked behind the dash.



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On the engine bay side, it’s an OEM harness, so everything plugs in really nicely. The only things worth mentioning are the hookups for the starter +12v and starter solenoid.

The OEM Honda charge harness includes the positive terminal for the battery, so we cut that off and crimped it to the OEM Miata harness. On the left are the two wires that normally fasten to the Miata starter, and on the right is the OEM Honda charge harness with the battery terminal cut off.

Attachment 231878

We used a big, screw-type connector and a huge piece of heat shrink over the top afterwards.

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The OEM Honda starter solenoid wire is actually routed through the engine harness and pinned to the grey body/dash connector. KMiata’s patch harness then provides a flying lead which gets routed back into the engine bay and attached to the factory Miata starter solenoid wire.

With that, the engine starts and idles. We still have a bunch of small things to get done – we’re going to add a remote idle valve and we still need to build coolant and heater hoses, but the heavy lifting is done.

We’re also working on a whole ton of other chassis work – XIDAs, a poly/SAE863 bushing setup, 6ULs, Blackbird Fabworx GT3 rollbar, Elise seats, full stereo system, and the list goes on and on. :party:

[desire intensifies]

don't know about texas but getting this BAR'd in california seems like a nightmare and i wouldnt blame anyone for not even trying.

Unfortunately I believe it would be barred in California.

Great thread. Ill be watching this with interest as my K24/20 is almost done and ready for the transplant.

Im looking at a dry sump option myself and had a question in reference to shaving the rack.
What part of the pan does the power rack touch?
the top of the 'hump' or one of the 'sides' (meaning fwd or rearward)?

if I have a flat pan, would it still hit?

david

I love this so much. When ive had enough if the BP I need to do this. Thank you for the impressive documentation. Many cats given.

I think even with a dry sump pan it would be tight. But the bigger concern would be pump placement. The Dailey dry sump would not work because it would hit the mounts and or steering shaft. There is not much room to the sides of the motor down low. This is why the normally alternator relocations can not be used.

Subscribed for useful info! Really considering this swap for the MSM!

I didn't look that closely. The pan was designed to be installed with a rack that was fully shaved/clearanced, so we did that before assembling the two. I can't comment on what would hit what if you go with a significantly different oiling system.

Fair enough.

Thank you bery much

Since this come up from time to time, it's worth mentioning that I've been working with Emilio and especially John at Hytech on designing a production version of the external wet sump system they built. Although it won't be the cheapest thing, there is demand for it.

In the mean time, our test car is still going strong on three years of track use. We threw an Accusump in the car last year for good measure, although I did an event without it a week ago without issue. It's a nice, affordable insurance policy though, and I'd recommend it for any K series track car, Miata or otherwise.

This is good advice, especially if you are running r-compounds on track. We have installed a lot of accusumps on our k-powered race cars throughout the years, from Grand Am cars to HPDE cars. They really are cheap insurance. They do add some complexity (extra oil lines, etc), but the result is worth the effort.

My k20 prelude is currently racing without one, and I've yet to have any problems, but I am planning on installing one sooner than later.

Great thread!

Love seeing how far David has come in the year since I got mine going. So much has been made turn-key, and the more street-oriented parts (header & intake) will make this more popular. I especially like the K_Tuner option since it is based on K24 hardware and does not require swapping so much of the K20 stuff over.

Not to derail the build thread, but a couple of things for those considering doing this swap:

1) A manual steering rack is still available from Mazda and the engine fits a bit easier that way. Personally, I like the slower ratio...especially on the street. Not cheap, but if you have a source for parts at dealer cost, its not that bad. If you get it from Mazdaspeed Motorports, you have to pay the core charge.

2) The OE TSX exhaust manifold can be made to work and is not bad (tubular, but short tubes). A little grinding on the flange and it fits right in there. Can save a few bucks that way, and can mate it up to pretty much any Miata exhaust after making a crossover tube similar to what David supplies with his header options. Further, the OE manifold has a heat shield...and these motors make a TON of underhood heat with exposed headers.

3) Bleeding air out of the cooling system is a challenge. David's rear water outlet has a bleeder hole that makes it way easier.

Thanks Andy! That's the focus for 2016 - to make this swap available to as many enthusiasts as possible.

The best solution here is to jack the front end of the car way up in the air. It makes it MUCH easier to get it burped.

Yup. Nothing new for me. Our crossflows are a little tough to get fully burped too. Throw the front end 18" in the air and use a magic funnel and it all comes out pretty easy. :party:

I use a lisle funnel setup and keep the front jacked up and I works like a charm.

Got all the suspension back into the car. The control arms get Energy Suspension bushings, SAE863 sleeve bearings, and 1144 steel sleeves. Low NVH, super low stiction. Big thanks to Bob Bundy for helping me out with this setup.

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Bauer Extended LBJs for added camber at sensible ride heights.

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In situ with Gen2 XIDAs and fresh Trackspeed brake lines. The car will run the OEM Sport brakes for now, but I suspect a Trackspeed 11.75” BBK will find its way in at some point. An RB tubular FSB, stock RSB, and Supermiata endlinks will round out the suspension setup.

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With all the coolant hoses built, we bled out the cooling system by lifting the nose into the air and using a magic funnel. It drank another half-gallon of coolant after the thermostat cycled, so everything did its job.

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Header starting to color up nicely. :party:

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Once it’s on its own four feet again, we will start to put the interior together. New tan carpet from Moss Motors will go with the tan Probax seats that currently live in my ‘02SE, christened “Acamas” (son of Theseus). Acamas will get a set of black Probax leather seats to match the black interior in that car. The Blackbird Fabworx GT3 bar has made several appearances in photos already, and a Robbins canvas softtop will complete the interior transformation.

What is maintenance like with these?

Pics of coolant hoses?

They are billed as "maintenance-free" but I'm not buying any bridges in Brooklyn this week. :) My expectation is for them to be fairly low-maintenance, though. If stiction increases over time, we'll evaluate whether or not to add some form of additional lubricant (the sleeve bearings are oil-impregnated already) or just plan to replace the sleeve bearings at regular (multi-year) intervals.

I will snap some next time I'm with the car.

Are you using any grease to keep crap out of them? That is the plan for mine.

I'm running a SADFab bronze bearing retrofit in 4 locations (delrin in the rest) I grease them just to keep junk out. In Oregon I get dirt and water and grime everywhere in the car, and the grease makes sure it stays out.

Similar to greasing delrin bushings, it isn't needed, but it helps with longevity.

The big bushing megathread has a lot of info covering all of it.
https://www.miataturbo.net/suspensio...cussion-87573/

Coming together nicely, and quickly. For coolant hose I don't see why more people don't run AN hoses it makes life much easier!

Because it'sapproximately 20 times the cost.

Not only does it cost more, it can be very problematic. I have used AN hose on my old race miata and on my Kmiata. And on both cars i fought with defects in the hose ends and warped flares from welding. I have had more leaks then i think i ever would have had with rubber.

Yes they look great and just unscrewing the line is nice. But when you buy $250 worth of fuel line and you have 5 leaks, it gets old fast. Now i run the aluminum seals on all my AN flares for good measure. And i don't buy the cheap summit brand fittings. I have even had issues with earls. My new favorite is fragola.