K24 Miata Swap Updates

[MarquetteLa]

Back in August I took three weeks off of work and drove my 2002 Miata from Colorado to my buddy Justin's place in Tennessee to swap a Honda K24A2 into the little roadster. The drive down was pretty uneventful, thankfully. The car hit 130,000 miles shortly before arriving at our destination.

Just about all of the parts we would need had already been delivered, but there was still some prep work to do. I powder coated my new front & rear tow hooks to match my new roll bar while Justin ceramic coated the KMiata exhaust manifold.

Then came the actual teardown. Justin started pulling components out of the engine bay while I stripped the interior.

This swap doesn't work with power steering (there's just not enough space for the hydraulic lines), so we took my steering rack apart to properly depower it, removing the internal seals and welding the pinion. Reassemble and bolt it to the new subframe!

With the dash pulled and the Mazda subframe replaced with the new KMiata subframe, it was time to crack the donor K24 open for its necessary prep work.

Engine prepped and ready for a new ACT HD clutch, specially-machined KMiata flywheel, and KMiata transmission adapter plate.

STAB IT

In the photo above, you can see the "hump" in the oil pan. The steering rack sits inside that hump. That's why you can't run hydraulic power steering with this swap; there's barely enough room for the rack, and none for the lines.

Motor mounted!! Let's mock up the manifolds and see how they look.

Pretty good! However, some of these clearances are awfully tight...

That's the transmission adapter plate about a hair's width away from the chassis. And this is the exhaust manifold collector flange nuzzling electron clouds with the subframe:

The engine mounts from KMiata are very stiff, so with some additional massaging these clearances should be okay.

And this is where we started to hit some stumbling blocks. Because I don't mind a little bit of functional ballast, I ordered KMiata's air conditioning kit. This A/C kit includes all new custom lines and fittings and brackets; you just have to source your own "universal" compressor, which KMiata identifies a part number for. The compressor I ordered, despite looking exactly like the compressor KMiata shows in their instructions, didn't quite fit KMiata's supplied bracket.

Justin was able to clearance the compressor a bit where it was making contact with the block and shimmed the mounting tabs with some washers to get it to actually mount up "properly".

Then we dropped in the "direct fit" Mishimoto radiator I ordered, only to find the passenger side mounting post wasn't really where it ought to be. We'll need to fabricate a new tab to reach the post.

At this point it was pretty clear that we weren't going to finish the swap in time for me to drive the car back to Colorado at the end of my three-week vacation like I had hoped. Bummer. But at the same time, we made the conscious decision to not rush the work or cut corners, but to do it right the first time, even if that means it takes longer. Could we have spent more time in the garage working on the car? Sure, but we also needed some time away from the project.

So, we decided that I would take a spare Honda Accord Justin had around back to Colorado while he finished the car for me in his spare time over the next couple months, hopefully in time for me to pick it up and drive back to Colorado before winter really set in. Have I mentioned what an amazing friend Justin is!?

Before I left Tennessee, we went ahead and installed my new Blackbird Fabworx NB GT3 roll bar since that's an easier job with two pairs of hands. Here's Justin, glad that we finally got it in place.

I really like this roll bar. The gold powder coat is a pretty darn good color match for my wheels, even if it doesn't look like it in this photo because of the uneven lighting:

That's the last photo I took of the car, back at the end of August. The car hasn't progressed much since then, because unfortunately about a month later, Justin had a low-speed motorcycle accident and broke his left wrist and right shoulder. He had surgery in October and started physical therapy a few weeks ago, so he's on the mend but it will take time. I'm just glad he's okay; racecars can wait.

So yeah, hopefully I'll be able to take some more time off of work next year to take the Accord back to Tennessee and finish the K24 swap in time to get some seat time with it in 2021.

And in the meantime, the Volkswagen R32 I just bought has developed a coolant leak! Joyous.

[pip bip]

@marquettela should've gone with the ford V8 swap

[A Former User]

@marquettela that seems like an ordeal and a half. Hope your friend recovers fully and that you can make the trip and finish the project.

Also just have to say that green and gold is a great combination.

[frinesi2]

Epic project. I love your color choices. That's going to be an awesome driver's car.

[S65]

@MarquetteLa Nice project, did you go with the K24A2 TSX engine? Or is it a hybrid build?

[Tripper]

@marquettela This is my favorite yata. Can't wait to see it all buttoned up! Also glad that your pal is ok!

[WhoIsTheLeader]

And this is the exhaust manifold collector flange nuzzling electron clouds with the subframe:

This phrase is amazing and I fully intend to steal it from you.

Nice work! British racing green with bronze wheels and roll cage is a classic color scheme and works so well on a Miata. Was there something actually wrong with the car or did you just want an engine that is as special feeling as the chassis?

[MarquetteLa]

@pip-bip said in K24 Miata Swap Updates:

@marquettela should've gone with the ford V8 swap

There are several reasons why I didn't go this route; one of which is cost.

@cataphract said in K24 Miata Swap Updates:

@marquettela that seems like an ordeal and a half. Hope your friend recovers fully and that you can make the trip and finish the project.

Also just have to say that green and gold is a great combination.

@frinesi2 said in K24 Miata Swap Updates:

Epic project. I love your color choices. That's going to be an awesome driver's car.

Thank you! I can't really imagine having any other color Miata at this point.

@s65 said in K24 Miata Swap Updates:

@MarquetteLa Nice project, did you go with the K24A2 TSX engine? Or is it a hybrid build?

Yep, it's a K24A2 from a TSX.

@whoistheleader said in K24 Miata Swap Updates:

And this is the exhaust manifold collector flange nuzzling electron clouds with the subframe:

This phrase is amazing and I fully intend to steal it from you.

Nice work! British racing green with bronze wheels and roll cage is a classic color scheme and works so well on a Miata. Was there something actually wrong with the car or did you just want an engine that is as special feeling as the chassis?

Haha, by all means! I've owned the car for 8 years now and have been autocrossing it the whole time. I feel that I'm getting damn near all the performance I possibly can out of the car with the stock motor, so it's time for more power. The K24 is a great platform with the potential for as much power as I could want in the future, but I'll be very happy for a while with double the power from a naturally aspirated motor.

[WhoIsTheLeader]

@marquettela said in K24 Miata Swap Updates:

I'll be very happy for a while with double the power from a naturally aspirated motor.

I can understand that. Is the K series a good bit heavier than the stock powerplant?

[MarquetteLa]

@whoistheleader The weight difference is pretty much nil. The K24 is an aluminum block, whereas the stock BP motor is an iron block. Once the swap is all said and done, I expect it to be around the same weight as before (2,224 lbs) or a little lighter.

[WhoIsTheLeader]

@marquettela So you get lots more power, more torque, possible add some lightness, and all you have to give up is serviceability, ease of service, power steering, air conditioning unless you're really dedicated, and a big hunk of cash. Seems worth it.

[Wrong Wheel Drive]

Wanna do another one for me when you finish? It is bound to be easier the second time lol. This sure sounds like quite the project! If it wasn't for covid preventing travel and if I had any marketable skills I'd offer to help in exchange for the gained skills to do the same to my miata.

[MarquetteLa]

@whoistheleader Yeah, that's about the size of things lol. I'm keeping A/C since it will actually have the power to drive it without making it feel like a pig in traffic. Losing power steering shouldn't be too bad in such a light car. And I'm not sure I'm giving up too much on serviceability -- it's just a Honda K24 after all. Reliability was one of my top priorities when deciding on this project.

[MarquetteLa]

@wrong-wheel-drive said in K24 Miata Swap Updates:

Wanna do another one for me when you finish? It is bound to be easier the second time lol. This sure sounds like quite the project! If it wasn't for covid preventing travel and if I had any marketable skills I'd offer to help in exchange for the gained skills to do the same to my miata.

LOL you'll have to ask Justin. There's no way I could do this on my own without his knowledge, skills, and tools. I'm beyond grateful for his help.

[CivicWagonEngineer]

Nice work! Any further plans for the engine or just keep it stock once it's in the Miata?

[WhoIsTheLeader]

@marquettela said in K24 Miata Swap Updates:

I'm not sure I'm giving up too much on serviceability

I was thinking more about actual ease of maintenance in tighter quarters than reliability.

[MarquetteLa]

@civicwagonengineer said in K24 Miata Swap Updates:

Nice work! Any further plans for the engine or just keep it stock once it's in the Miata?

Thanks, the first order of business is to get seat time with the new motor and re-learn the car. I'm sure I'll get bored with 220 whp vs 110 whp eventually, but it won't be for a while.

@whoistheleader There's not really that much difference compared to the stock motor in terms of working space in the bay. There's actually a bit more room now that some parts have been removed, like the strut tower bar and mounts (it won't clear the K24).

[davesaddiction]

@marquettela Moved to Best of OPPO.

[MarquetteLa]

@davesaddiction Thank you!!