Hi everyone. I have a question for the Honda K24 experts as I'm having a hard time getting an actual clear answer from searching on Google. I'm currently planning to purchase a K24A JDM engine from a JDM engine depot about 2 hours from me for my K swap r50 MINI. Now, on their website, I see there are K24A RBB1 engines and K24A RBB3 engines. From my search, it seems that the only difference between the 1 and 3 are the casting date, otherwise everything else is the same?
Do all JDM K24A engines have actual VTEC like our USDM TSXs and not the "eco" VTEC that our USDM 7th gen Accords came with? Is there an easy way to tell that I'm getting whats advertised when I go to look at the engine?
Alternatively, if anyone has a lead for a lowish mile K24A2 out of a TSX near PA/DE/MD/NJ/NY thats not too expensive, I'm all ears as well. 
Sonic
UberDork
3/12/25 9:54 p.m.
All the JDM K24 RBB motors have proper performance VTEC. Not sure the exact differences between RBB1 and RBB3, I have a K24A2 from an 07 TSX in my Civic, it is wonderful.
In reply to Sonic :
Thanks! So sounds like, as long as the head has the RBB stamp, it *should* have the proper performance VTEC? I guess I can also try and peak into the oil fill cap and try to see if I can count 3 lobes on the cam.
No appreciable difference between RBB1,2,3. But RBB on the head is the key.
If the place is only two hours away, they should have no problem with you popping the valve cover off to verify both the presence of the three-lobe cams, but also to inspect the general nature of the engine internals.
Look for pitting on the cams, which can happen if the car sat for awhile in a moist climate. Or perhaps really gunked up oil, if it had never been changed -- I had one like that.
You can also easily take off the exhaust and/or intake manifolds to eye up the combustion chamber insides. Or if you have a boroscope/endoscope tool, you can peak in through a spark plug hole.
You don't want any surprises.
As for low-mileage USDM TSX motors? Good luck with that. :)
Best option for that one is LKQ -- they are nationwide and can ship stuff around between locations.
PS: Another option that has started to pop up is imported Euro spec K24A3 motors. Same basic engine. The JDM supply is getting thin and what remains are not always in the best shape.
Andy Hollis said:
No appreciable difference between RBB1,2,3. But RBB on the head is the key.
If the place is only two hours away, they should have no problem with you popping the valve cover off to verify both the presence of the three-lobe cams, but also to inspect the general nature of the engine internals.
Look for pitting on the cams, which can happen if the car sat for awhile in a moist climate. Or perhaps really gunked up oil, if it had never been changed -- I had one like that.
You can also easily take off the exhaust and/or intake manifolds to eye up the combustion chamber insides. Or if you have a boroscope/endoscope tool, you can peak in through a spark plug hole.
You don't want any surprises.
As for low-mileage USDM TSX motors? Good luck with that. :)
Best option for that one is LKQ -- they are nationwide and can ship stuff around between locations.
PS: Another option that has started to pop up is imported Euro spec K24A3 motors. Same basic engine. The JDM supply is getting thin and what remains are not always in the best shape.
Thanks I appreciate all the info! They'll probably let me walk around and look at a few of the engines if they're reputable I'm sure. They have decent enough reviews so we'll find out.
They do have some K24A3 engines as well. So they're the same thing then? Same internals, oil squirters, all of that?
Japanspec said:
They do have some K24A3 engines as well. So they're the same thing then? Same internals, oil squirters, all of that?
Essentially, but not exactly.
Some info here: https://en.wikipedia.org/wiki/Honda_K_engine
Andy Hollis said:
Japanspec said:
They do have some K24A3 engines as well. So they're the same thing then? Same internals, oil squirters, all of that?
Essentially, but not exactly.
Some info here: https://en.wikipedia.org/wiki/Honda_K_engine
So from that link it seems like a bit lower power but a bump in torque? Didn't see much about internals though unless I missed it.
Japanspec said:
Andy Hollis said:
Japanspec said:
They do have some K24A3 engines as well. So they're the same thing then? Same internals, oil squirters, all of that?
Essentially, but not exactly.
Some info here: https://en.wikipedia.org/wiki/Honda_K_engine
So from that link it seems like a bit lower power but a bump in torque? Didn't see much about internals though unless I missed it.
Most likely due to different exhaust/intake manifolds, which you are going to change anyway.
More info: https://www.drifted.com/honda-k24/
Andy Hollis said:
Japanspec said:
Andy Hollis said:
Japanspec said:
They do have some K24A3 engines as well. So they're the same thing then? Same internals, oil squirters, all of that?
Essentially, but not exactly.
Some info here: https://en.wikipedia.org/wiki/Honda_K_engine
So from that link it seems like a bit lower power but a bump in torque? Didn't see much about internals though unless I missed it.
Most likely due to different exhaust/intake manifolds, which you are going to change anyway.
More info: https://www.drifted.com/honda-k24/
Awesome thank you Andy! This link was also very helpful. I appreciate your insight, I'll keep the K24A3 in mind too then when I go to make my purchase.
I reiterate what everyone else has said so far.
We just bought a K24A2 powered TSX for Champcar. First thing I did when inspecting it was to pop the valve cover off, check for the RBB casting, the cams, etc.
What are your plans for the engine? Keep it as is? I would inspect the tensioner and probably just go ahead and replace it along the VTC gear with a new Honda unit. I would also check the phasers on the back of the cam, I found a loose one that also had one of the teeth worn down. It also had a broken tooth on the crank trigger wheel, which explain a lot of the issues with starting it. Other than that they are solid engines that respond well to things like cams, where you can easily see 300whp.
DirtyBird222 said:I would inspect the tensioner and probably just go ahead and replace it along the VTC gear with a new Honda unit. I would also check the phasers on the back of the cam, I found a loose one that also had one of the teeth worn down.
Not to be pedantic but...
The VTC gear on the front of the intake cam is the cam phaser.
The back end of the cam has pulse plates, which provide signal for the cam position sensors. And yeah, I've found a loose one before.
Andy Hollis said:
DirtyBird222 said:I would inspect the tensioner and probably just go ahead and replace it along the VTC gear with a new Honda unit. I would also check the phasers on the back of the cam, I found a loose one that also had one of the teeth worn down.
Not to be pedantic but...
The VTC gear on the front of the intake cam is the cam phaser.
The back end of the cam has pulse plates, which provide signal for the cam position sensors. And yeah, I've found a loose one before.
Yea what this guy said by being pedantic. My brain was still mush after being at Sebring most of the last month.
Either way, good to check all of those things or do preventive maintenance and while you have the engine out of the car.
Here's what the exhaust pulse plate looked like when we started diagnosing starting issues. Also the crank trigger wheel
Here's what the exhaust pulse plate looked like when we started diagnosing starting issues. Also the crank trigger wheel
That damage is really bizarre for a stock-unopened engine. I've seen those things before but only on modified, high revving engines with dubious workmanship.
In one case, it was my own workmanship 
Oh nice thanks for this additional information! I'm going to do a full service on it before it hits the car so I'll make sure I check all of that.
As for plans, I'm going to run it N/A for awhile and then I'm planning on going turbo to maybe hit 400whp as I heard that's possible and decently safe on the stock internals. I have to figure out which transmission I want to use though, so I guess that will be another limiting factor. Not sure which of the K series transmissions would be best without breaking the bank.
