I know there are a ton of K24z3 people on here. I need a new motor for my K miata. The JDM motors seem like the way to go however in Japan the k24z3 is instead called a K24A. All of them so far I have seen are R40 blocks and heads.

The JDM motors are available with as little as 10 to as high as 11:1 compression.

How do I find and verify I'm buying the 11:1 compression version?

 

I would be interested to know this. I ended up with a JDM version of the K24Z. I think I went down a rabbit hole and determined that they were all 11, but I can’t recall that logic, and it may be flawed. I haven’t put this motor on the dyno yet, but with the tune from my OG TSX K24Z3, it drove great this past weekend at Sonoma.

edited to add: sounds like you lost your K24Z, how’d that happen?

 

I have been researching this for the past few hours and what I have come across so far suggests that for the US engines the difference in compression comes from the pistons alone. R40 gets you 10.5 and RL5 11:1. That would be visible with a boroscope assuming there wasn't too much carbon buildup.

Someone on another forum posted this link which has some teardown of a single port jdm k24a:
https://www.driveaccord.net/threads/...3#post-6928113
That JDM motor has flat top RLF pistons which look very low compression. Google suggests the RLF came in the CRV and was 10:1.

At this point I'm thinking my best bet is to pull a plug and look inside for the piston letters.

Not sure what happened on my motor for sure until I tear it apart but there is a hole in the side of the block. My tuner noticed some gouging where the crank pulley bolt was hitting the sway bar under braking. This would cause a lot of wear and tear on the thrust bearings. I was planing on fixing it in the next month when I had the splitter off. This past weekend I had a hard off and when I came back on there was a lot of vibration and the car was really hard to shift. Soon after the motor popped, spewed oil on the drivers suspension and spit out flames. My theory is the thrust bearings wore out and the crank was walking and pushing into the trans input shaft.