JDM k24a build for 97 miata swap (250-280whp goal) - K20A.org .:. The K Series Source . Honda / Acura K20a k24a Engine Forum
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Old 07-07-2019, 12:31 PM   #1
WannaBeK24
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Default JDM k24a build for 97 miata swap (250-280whp goal)

hi all, i've just ordered a JDM K24a from Hmotors. should be here within a couple weeks. I've also ordered all the pre-install motor prep parts from Kmiata. things like the custom oil pan and type s oil pump etc. David @kmiata recommended drag cartel 2.2s and or 3.2 cams. My goal is track reliability making somewhere around 250-280whp and maybe 210ft lbs of torque if possible? I've through a few builds and wow does the K series have a lot of options. im used to my miata with only like 2 big vendors i trust... my only honda experience is the H23a1 from the 96 lude i had (epic car imo) and i never got to build that since i was a broke high school kid at the time.

but back on topic, what will i need to make this a bullet proof all motor build? i've read through a few builds and i see all sorts of things but don't want to waste money on things that won't really need to be replaced. this motor doesn't need to be over built to handle 400hp.

basically Kmiata claims around 220whp with
-a stock k24a2 with their manifold (was skunk2 ultra street but ill be getting their cast aluminum RBB with 74mm TB)
- their race header (4-2-1 they claim it supports 300whp builds)
-i'll run previously mentioned header and cast mani with a custom 3" inch exhaust
- hondata kpro4 from Kmiata
what i am iffy on from here is to reach my goal range, what else will i need? will the valvetrain need upgrading? will i need to upgrade rods/pistons? is sending my head in for a port/polish necessary? i will mention i want to stay on 93 pump gas. i assume ill want bigger injectors? any and all help and constructive criticism is appreciated.

EDIT: i should add that i am just lost in whats mandatory for reliability and whats just "added security"
and also, i have the 50 degree VTC as well. as i go i will try to take pictures of my tear down and all that jazz. i suspect this build will take a while. if anyone is interested, ill post pics of my miata. not sure i have many of when i first got it, but i have since painted it Nardo Gray (work in a small body shop that specializes in restorations. from a 48 chevy fleetline, to a RHD 300xz)

EDIT #2: will also mention i am in washington state about 200 ft above sea level. so no mile high elevation issues there haha.

Last edited by WannaBeK24; 07-07-2019 at 12:40 PM.. Reason: adding to post
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Old 07-10-2019, 06:55 PM   #2
WannaBeK24
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Default Re: JDM k24a build for 97 miata swap (250-280whp goal)

bump.
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Old 07-11-2019, 09:49 AM   #3
FastG
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Default Re: JDM k24a build for 97 miata swap (250-280whp goal)

I have a K-Miata setup in a locost 7. I have a early 4-2-1 K-Miata exhaust, KPro, S oil pump, 50 degree can actuator, RBC inlet manifolf, with a 70mm throttle body. On a high end eddy current dyno it came out a 220rwbhp and 209tq. So Dave's numbers are good.

Graham
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Old 07-11-2019, 10:50 AM   #4
WannaBeK24
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Yes I didn't think David would be lying about their numbers. Just am unsure what all I would have to do to make around 250-270whp. Port/polish? Bore the block? Do I need to upgrade my rods if I go 12.5:1 CR? Does the valve train need to be upgraded? Was going to go DC 2.2 or 3.2 cams.
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Old 07-11-2019, 11:20 AM   #5
Scider
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Default Re: JDM k24a build for 97 miata swap (250-280whp goal)

I'm currently building an Exocet, with plans of swapping the motor in a year or two to a K24 build. I've been doing a lot of research on how to get to the magical 300 whp number which I plan to get to in stages.

That said, I found these articles particularly interesting:
http://www.superstreetonline.com/how...x-k24a2-engine
https://kmiata.com/blogs/news/k24a2-dyno-testing

You'll definitely need cams to find an extra 30-50 hp. I haven't looked into the milder end of things, but there are options that use the stock valve train, and more aggressive options that require upgraded springs.
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Old 07-11-2019, 11:47 AM   #6
WannaBeK24
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Yes 300 all motor is an expensive feat. I just get lost cuz every rattles off so many different items like X brand of rings and Y brand of this and that and I'm lost wondering if all these things are necessary or if they are WAY over building the motor.
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Old 07-11-2019, 09:41 PM   #7
Lotus
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Default Re: JDM k24a build for 97 miata swap (250-280whp goal)

300 wHp is doable, but only for a top spec build.
As you need high rpm (8k) for these numbers, you need forged pistons, cams, springs to cope with the high lift long duration cams, suitable oil pump, suitable cylinder head, injectors, fuel pump, suitable intake manifold, suitable exhaust system.


You need scary average piston speeds on a K24 to reach these numbers.
Donít expect a K24 build with 300 wHP to last forever on trackdays reving 8000 rpm all day.
At this power level most want some kind of limited slip diff. For a mighty K24 build you might also consider a 4.3 final drive unless you want to do do donuts in 3rd.
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Old 07-11-2019, 09:54 PM   #8
WannaBeK24
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Yeah I am looking for 300. More like 260-270 would be ideal. Would I need to upgrade valves and springs? Also would prefer a solid power curve and have decent mid range power. What cams should I run for that? I've heard good things about prayoonto but everyone only mentions their stage 4s.
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Old 07-12-2019, 06:16 AM   #9
Scider
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Default Re: JDM k24a build for 97 miata swap (250-280whp goal)

Yeah, reaching 300 whp definitely requires a carefully built engine with forged pistons and upgraded rods, head work, cam selection, and an intake and exhaust system that compliment each other to put the tuning peaks where they need to be.

I hate referring to cams by stages, but any "stage 4" cam will require at the least stiffer valve springs with associated retainers/keepers/spring seats.

Here's another build thread (K20/K24 motor) using factory parts. Looks like the motor reached 254 whp @ 7500 rpm in a RWD format with Prayonto stage 2 cams:
https://www.k20a.org/forum/showthread.php?t=165538

And a fantastic history from MrSideways on the history of reaching 300 whp in his S2K:
https://www.s2ki.com/forums/automoti...years-1175851/

Long story short, he ended up with a built K24 from 4Piston and a set of their RR3 cams to break the 300 whp barrier.

Last edited by Scider; 07-12-2019 at 06:20 AM..
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Old 07-12-2019, 06:20 AM   #10
WannaBeK24
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Yes, referring to them is stages gets confusing. I will check out that link when I get a break at work. Any suggestions on a mid range power cam for my power goals?
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Old 07-12-2019, 06:30 AM   #11
WannaBeK24
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Good info in that thread! I'll check out the s2k one later. Man I wish I could blow the budget and build a nasty motor! This is the very first time I get to tinker with a motor like this. I'm so stoked 👍 a littler nervous about checking clearances and all that but I got buckets of time before it even can be swapped into the car.
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