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Discussion Starter · #1 ·
Hey Guys, I've been lurking around for awhile planning my build and trying to learn as much as I can about the K-series engines. I've got everything planned out for the most part, but wanted to see if anyone can give me some guidance. First off, my goal is to be around 270HP all motor with a jdm 02-04 TSX k24a2.

I plan on doing a full head rebuild (valves, springs, cams, cam gear, etc), upgraded fuel system, TB, etc. etc. I already have full bolt-ons installed on my RSX (base) as well.

My main question is about the bottom end. I really want to get in there and get some hands on experience "rebuilding" the shortblock, but I'd rather keep the stock pistons/rods since I'm not trying to go super crazy on my first build. Seems like a slippery slope with replacing components when you start to disassemble the bottom end.

So my question is: Is it safe to disassemble the entire short block, clean, and re-use the piston/rods? I would want to replace all bearings and piston rings for peace of mind. But can I hone the cylinders and slap the oem pistons back in? Would a hone still keep me within the piston-to-wall clearance?

**I tried searching the threads for an answer to this question, and I found a lot of related threads, but no definitive answer. Thanks in advance everybody!
 

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@LotusElise can elaborate more than I can on this subject I’m sure but I will offer my personal experience.
-you can take the pistons and rods out safely and clean them to be re-used
-you “can” also re-use the rod bearings if they are not scored /burnt and go back in the same rod they were removed from
-you can hone again on a stock bore and keep it within tolerance.
-it is also possible that the oem bore is out of round and once you take the piston out it will not go back in , usually it is advised to bore .5 over to ensure you have a perfectly round cylinder for your new rings to seat on.
-I have seen many motors taken apart and re-ringed/new rod bearings on the existing pistons and rods and then put back together just fine if there is no damage inside the engine. Even 200k+ engines.
 

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Discussion Starter · #3 ·
Thanks for the reply @KBuilt. That's the answer I was hoping for. So if it does turn out to be out of bore and I have to bore 0.5 over like you said, would I need to upgrade to larger pistons? Or would that still be within tolerance to just add new rings?
 

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Discussion Starter · #6 ·
I'm assuming that a jdm k24a2 longblock with lower miles will be less likely to be out of round, fingers crossed. In my case since I'm planning on re-using pistons/rods I think it's worth the extra money, rather than trying to pull from a junkyard. Solid advice @KBuilt, gracias.
 

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Arouse the DAMPFHAMMER!
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First off, my goal is to be around 270HP all motor with a jdm 02-04 TSX k24a2.
Not very likely on a stock block as long as you want to keep it reliable. Redline should be kept below 8000 rpm, which may lift your engine with good bolts on and cams and head work to 260 whp. But 270 whp need definitely a better intake manifold (not available on the aftermarket) or a built and forged high CR block to be able to utilize bigger cams potential and the higher redline reliability.

...I would want to replace all bearings and piston rings for peace of mind. But can I hone the cylinders and slap the oem pistons back in? Would a hone still keep me within the piston-to-wall clearance?
If you dismantle the short block it is time to upgrade it. The time and the money is worth to think about doing a serious OEM like built or an forged high CR built. The only reason to dismantle it complete and assemble it together again without maintenance is measuring every single clearance to prove the no-change-of-maintenance parts is the right one.

Recommended Procedure:
  • doing a leakdown test before dismantling anything
    • if below 4 % leave it
    • if above 4 % think about it
      • think about which system leaks and how much
      • think about the next step to investigate it. If there are open questions, then...
  • dismantle the head, measure all valve clearances, the valve seat center deviation and measure the roundness of the bore with the help of the torque plate
  • if the rings were the leaking system, dismantle the short block
    • measure all clearances and replace parts accordingly
    • regarding the hone structure, when need of another hone process and you aim for a 270 whp goal you need to go to the next or more oversize of the piston. Stopp at 87.5 mm at the stock block. You may go to 88 mm, but don't wonder if the block have bigger blowby and less power.
Sure you can hone and install the old pistons with new rings back, but every hone process is done based on to key criterias: shape and roughness/hone structure. If a honing is necessary it's very likely the bore size increases by almost a 1/10th of a millimeter (around 0.08 mm for a pre and final hone). The stock piston to liner clearance is around 0.038 to 0.051 mm (0.0015" to 0.0020"). I don't think it's a good idea to double the piston clearance, beside you just fine hone it which increases the bore by around 0.02 mm. But that makes no sense if the bore is out of round.
 

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Discussion Starter · #8 ·
Stopp at 87.5 mm at the stock block. You may go to 88 mm, but don't wonder if the block have bigger blowby and less power.
So the only way you should go higher that 87.5 is if you have a sleeved block?

Just a few things I'm still a little unsure of:
1. Are you saying the only reason I would have to remove the pistons is if the leakdown test was above 4% AND the issue wasn't solved with inspecting other systems like the head?
2. Say the leakdown test is under 4% but the cylinder walls are glazed, is it worth a fine hone and re-install original pistons? Or should it be left alone because it's a possibility like you and @KBuilt said, that once the piston is out the cylinder could be out of bore and I would need to bore and replace pistons anyway?

Thanks for the reply @LotusElise, I've been reading a lot of your other posts and I appreciate your expertise (y)
 

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So the only way you should go higher that 87.5 is if you have a sleeved block?

Just a few things I'm still a little unsure of:
1. Are you saying the only reason I would have to remove the pistons is if the leakdown test was above 4% AND the issue wasn't solved with inspecting other systems like the head?
2. Say the leakdown test is under 4% but the cylinder walls are glazed, is it worth a fine hone and re-install original pistons? Or should it be left alone because it's a possibility like you and @KBuilt said, that once the piston is out the cylinder could be out of bore and I would need to bore and replace pistons anyway?

Thanks for the reply @LotusElise, I've been reading a lot of your other posts and I appreciate your expertise (y)
My best advice I could offer is to not take apart the bottom end unless it -needs- it. (Unless you are prepared to build with aftermarket parts) There are quite a few instances where 270 whp was made with a stock k24 block , but the head work was extensive, k20 oil pump, top of the line intake manifold,a nice set of cams and a great header/full 3” exhaust and usually e85. It would be much easier to hit your goal with a higher compression rating , but pistons and machine work , bearings gaskets etc all adds up. I would write down a list of all possible routes you want to take after going through the all motor dyno/stock block k24 dyno threads and add up the prices of all your parts and expected machine work etc To conclude the best route to take for your engine.
 

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Discussion Starter · #11 ·
Thanks, that pretty much boils it down for me. I have a list parts needed for various options I've been thinking about. At first I had planned on rebuilding the entire bottom end, but after looking at the price tag I thought I'd look into more budget friendly options haha which is why I asked you guys. I know I'd be happy with a stock k24a2 in my RSX, but I'd really like to tear down something and learn some hands on stuff. Sooo I'll probably end up going high CR pistons and just clean up the head. Really appreciate the advice!
 

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Very Nice! 277 on a stock block. I've watched Keep Gunnin videos here and there. Gotta look a little bit more into his setup.
It actually cleared 280whp. I used to watch his ole street racing videos when I was younger and am happy with how the content evolved. There’s a library of k swap and k series how to in those videos.there were many things on my swap I hadn’t done before and through that channel learned and executed on my car. Very valuable in my opinion.
 

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Thanks, that pretty much boils it down for me. I have a list parts needed for various options I've been thinking about. At first I had planned on rebuilding the entire bottom end, but after looking at the price tag I thought I'd look into more budget friendly options haha which is why I asked you guys. I know I'd be happy with a stock k24a2 in my RSX, but I'd really like to tear down something and learn some hands on stuff. Sooo I'll probably end up going high CR pistons and just clean up the head. Really appreciate the advice!
A high compression k24 with a stock head would be a world of fun , try to get either a 05-06 k20z1 or 06-08 tsx intake cam with a 50 vtc to go with it 👍 best oem options , all k24 exhaust cams are the largest and the same spec.
 

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Arouse the DAMPFHAMMER!
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It actually cleared 280whp. I used to watch his ole street racing videos when I was younger and am happy with how the content evolved. There’s a library of k swap and k series how to in those videos.there were many things on my swap I hadn’t done before and through that channel learned and executed on my car. Very valuable in my opinion.
Nice video and a hell of power out of a stock block .

Stock pistons and peak power at 8350 rpm, redline somewhere at 8500 rpm . That lasts not for ever on every application. My idea of a safe peak power would be 7800 rpm and redline it at 8200 rpm for a DD, for a race car 7900 rpm should be redline and peak power engine speed at 7500 rpm.

The issue is the side load wears the hone structure at that high engine speed. As soon as the hone left enough the friction increases, the piston heats up and the seizure begins, combined with knock and soon the rallye will begin and end up in a piston seizure or knock drama. I don't like drama .
 

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Nice video and a hell of power out of a stock block .

Stock pistons and peak power at 8350 rpm, redline somewhere at 8500 rpm . That lasts not for ever on every application. My idea of a safe peak power would be 7800 rpm and redline it at 8200 rpm for a DD, for a race car 7900 rpm should be redline and peak power engine speed at 7500 rpm.

The issue is the side load wears the hone structure at that high engine speed. As soon as the hone left enough the friction increases, the piston heats up and the seizure begins, combined with knock and soon the rallye will begin and end up in a piston seizure or knock drama. I don't like drama .
Ya they are definitely pushing the envelope, who knows how long the block will last like that, but assuming the tune is spot on I would proceed to beat the guts out of it lol 😆. It has a 4piston tsx head, skunk tuner 2 cams with the ultra center feed and 90mm tb. Expensive but effective combination
 

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Arouse the DAMPFHAMMER!
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Ya they are definitely pushing the envelope, who knows how long the block will last like that, but assuming the tune is spot on I would proceed to beat the guts out of it lol 😆. It has a 4piston tsx head, skunk tuner 2 cams with the ultra center feed and 90mm tb. Expensive but effective combination
Maybe I did too much reliability engineering in my profession 😆. If a seizure is included in that fun, than I wonder why the don't built the block too. Maybe just to have the most powerful stock block setup? Everything for the show and the fun. Also an approach to run engines 🤭.
 

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Maybe I did too much reliability engineering in my profession 😆. If a seizure is included in that fun, than I wonder why the don't built the block too. Maybe just to have the most powerful stock block setup? Everything for the show and the fun. Also an approach to run engines 🤭.
I believe they were purposely leaving the block stock and just guiding the head in an attempt to keep the reliability somewhat there, oem Honda blocks can really take it, I’ve been sending it for years 😂 I want to take a similar route with my k24a, making power on stock block costs tho $$$
 

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I believe they were purposely leaving the block stock and just guiding the head in an attempt to keep the reliability somewhat there, oem Honda blocks can really take it, I’ve been sending it for years 😂 I want to take a similar route with my k24a, making power on stock block costs tho $$$
They build those cars to give them away, the previous ones had a CSS 12.5:1 k24 block and a 13:1 88mm block in the 2 previous giveaway cars, both made 300whp one motor had old skunk stg 3 and the other DC STAGE 4 cams. Those guys do a nice job
 
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