Hello and welcome.
I‘d have the block sleeved for that power if it used in anger on circuit tracks or serious drag racing.
Epoxy filling a block is not a thing to be done on a Honda K-series.
For the occasional street pull, even the stock block will do.

if you already got a full k20a2 engine, you have an ideal platform for a high power turbo engine. I’d skip the k24 block in this case.
Be aware that wiseco‘s normal piston pins are weak. We recently had a failure with them bending and one desintgrating despite them offering that pin on request about the intended use.
In terms of springs, the classic Ferrea K-series springs will do. If you settle on 400 HP, even fully stock springs are fine.
At these boost levels, you might benefit from aftermarket cams with more lift and duration to require less boost for the power. But the k20a2 stock cams are OK even for 500-600HP with the right turbo.

for such a high power build, I’d go fully programmable such as a Haltech R3 or R5 or a Link or Syvecs ECU. These all offer very fast knock control and nice things like DBW throttle control incl. using a DBW as a boost control option for launch control. For a 600HP tune, I’d not tune the car myself as a beginner. You’ll blow it up. These advanced ECUs are also not as easy to comprehend as the Honda OEM ECUs (Hondata), but don’t come with the limitations either.

if you intend to get these 500-600HP to the tarmac, you WILL destroy the stock gearbox in no time, likely on the very first pull. 4th gear failures start somewhere around the 350 to 400HP range, if you are gentle. Gear-x and Mfactory offer more affordable options compared to PPG. Some go sequential at that point or doing DSG conversions. But if PPG money is out of the question, don’t bother with these ideas either.

To get tracking at these power levels, you need to run low ride heights, superwide and super sticky rubber, a decent clutched limited slip trans such as a OS Giken and a good clutch system. You might even have to start looking into twin disk clutches. AWD would reduce tire requirements.

You need to spend a lot of research before spending any $ on this build.
Best to build this thread to home in on expectations, budgets and specs.

 

Okay thank you so much for taking the time to answer. I looked into awd but most likely wouldn’t be doing it until later down the road. I’ll take everything you said into consideration and I have the k24a2 block not the k20a2. And I’m not going for a track/drag build just a street/rare track build. The trans answered a lot of my questions. Also sorry for the sloppy write up was super late and half asleep I have a bit more of an idea on the things I spoke on then I made it seem. Very useful information thank you will keep updated.

 

Be aware we have opinions here and that not always agree with each other at all times.
My common approach for a first turbo build would be to start with a 350-400HP build that can use a full stock engine.


Or in your case a K24/k20 Frankenstein. Stock cams, stock springs, stock tranny except fitting a limited slip diff.
If you invest in a decent exhaust manifold you can later fit a larger turbo for those more like 20 PSI vs. sticking with 9-12 for now.

The performance will already be ballistic. You'll learn how to sort your turbo build incl. heat management, mapping etc.
Once you have run this for a year without fires, leaks etc., build an engine block and a tranny for your spec and swap bottom end and tranny out. Then add boost. If you still have the desire to. 400 HP Civic is already more than a handful on full chat.
You'll spin the wheels until at least 3rd gear if you don't employ boost by gear. Add an other 100-200HP and you'll spin the fronts even in 4th and way past 100 mph.

 

Hey so quick question i ended up going the route you mentioned starting off stock then upgrading. My 92 civic has a tucked gsr wiring harness can I just buy like the hybrid racing universal k swap harness conversion and would it be fine the gsr harness is already installed.

 

this is how a conversion harness is done for the 02-04 ECUs and engines.

https://www.doctronic.at/download/K-Swap%20Harness.pdf

As an engine harness you need a K-series harness. Best are OEM harnesses. Be aware that chinese “tucked” engine and conversion harnesses cause a lot of trouble and headaches. Unless you are inclined to fix electrical problems, stay clear of them. Swapped pins and poor connectors take ages to debug and fix, not always, but most of the time.

 

Okay more questions this guy that’s local to me needs to get rid of his aem series 2 for super super cheap which raises a lot of red flags he said it’s for k series but I have only done research into hondata. Do the aems lock up after use? Or does it even work with what I want tried looking for information online but not much I could find again thank you for all the help and time you have taken to answer my questions

 

Race Technology Knowledge Base | ECUType / AEMSeries2

a standalone does not lock up after use. Why should it. Some have password options, but they can be reset to factory spec in that case.

if you are on your own, this may be money and time well spend:

Learn how to tune AEM series 2! — Evans Performance Academy

Learning how to tune with AEM series 2 has never been easier! Our step-by-step online training course shows you every detail you'll need in order to become a AEM Series 2 tuning pro today!

www.evansperformanceacademy.com

It is an older ECU, but still capable. Pricing should be significantly lower than a new KPro or standalone.
Main benefit it offers is huge flexibility and real time programming while the engine runs. How much is he asking for it?

AEM Series-2 Plug-n-Play EMS for Honda/Acura K20A-Z, D17A1/A2 (Drive-by-cable)

Manufacturer: AEM; Product: Series-2 Plug-n-Play EMS; Make: Honda/Acura; Model: Civic, CRX, Del Sol, Integra, Prelude, RSX; Year(s): 1988-2006; Part Number: 30-6030

www.theboombopshop.com

 

He listed it for 500 but I’m over an hour away so he agreed to 400

 

for that price I think it is OK, especially given a KPro is like 3-4x that

 

set-up manual:

https://www.turbo-total.com/media/pdf/c1/e3/aa/30-6030-Series-2-Plug-Play-EMS.pdf

 

Okay thank you so much genuinely so grateful for your help

 

subra, but set-up will be similar:

https://www.supraforums.com/threads/aem-series-2-knock-control-setup.675960/

 

ended up getting it brand new. Been watching videos and listening at work on aem tuning and the basics EPA huge help. going to also dive deeper into wiring harness now that I know what I need. Also the z3 head is all prepped lubed and oiled. Going to get new hardware and gaskets. I do need to service the pistons ill add a photo the walls are good a glaze over them but clean. I dont know what to do with the pistons I dont really know what bad wear looks like or if i should clean them and reuse or just buy upgrade. Thank You again

4 is closest to the fly wheel

3&2

4

next two are 1

 

the piston pictures do not show?

 

Okay will take more when I get home from work and reupload. Do you know anything about this wiring harness K20 K24 K-Series Tucked Engine Harness For Honda Acura website owner was promoting on market place and I decided to message. He’s out of Europe. Been told by you and others not to cheap out on a harness is this considered cheaping out / Chinese harness. Or should I just save my self the trouble and get like a rywire one or more expensive one?

 

that loom is sold out and looks identical to the chinese "tucked" harnesses sold for <$100.
It is also too cheap to be made in the west.
These "tucked" harnesses are a common source of hard to diagnose and fix electrical issues.
I suggest a search here for "tucked" and "swapped pins"

Best looms are OEM or for the same quality western made aftermarket loom. But they cost >$500.
If you are on a budget get a base RSX auto loom and strip out all the auto tranny wires.
if you are on a half budget, get a 02-04 RSX-S loom or the k24a2 TSX looms.

 

Okay lil update tried pulling a wiring harness out of an 02 rsx from the junk yard but spent like 4 hours doing it and then they closed so they kicked me out gonna try again on Thursday on my day off but the pistons gonna try to reupload them. My guess is going to be they need to be replaced and if so I’m just going to upgrade and go low comp but then if I do pistons rods are needed aswell which I’m okay with. Just scared about trans might save up and go for a built one but don’t want to drop 5k+ on one also traction issues. Might just go with stock piston and rods if they are cheap but if they are even kinda close to low comp ones I’ll just replace.

 

Hello! Little update haven’t given up yet! Things I have picked up, 02-04 harness with a k tuned step down I got ALL my gaskets and all my new timing stuff (guides/chains/ect) and arp head studs. Going to buy my trans today had a few questions before I go get it after work today I’ve read mixed things about the k20z3 6 speed lsd. Is this not the optimal for boost bc of the shorter gears? Or is the ep3 better bc wider gears? And please correct me if I’m wrong I will need to change out the selector and cables correct? I’ve seen there’s different options for changing out the selector most likely going with k tuned. I’ve gotten a good grasp of the engine and head swap but being completely honest I know jack about transmissions so any information will be helpful been trying to read up.

 

 

Completely missed the gear changes they don’t match to the z3 stock ratios bc they are the tsx ratios should this be fine for boost

 

I gotta be stupid or something answered my own questions the gear ratio is better in the tsx will hold better and it has the lsd from the z3 in there so best of both world’s apologies for the spam

 

EP3 used a different selector mechanism (switch block) on top than a z3 gearbox. They can be swapped. The difference is in the direction of the throw.
For you 500 to 600HP, the stock ratios don't matter as you need a stronger gearset anyhow. Gear-X, PPG, MFactroy, etc.
Or go down to 400HP. Then they will just about work if you are symphatetic while shifting and launching.
That power is also about all you manage to get on the tarmac anyhow unless you go really wide and low on super sticky tries at the front. Boost by gear is your friend.
Who cares about power that only spins the wheels in 1st to 4th gear?

 

Hello! Quick couple-month check-in — haven’t picked up much since last time. I did end up getting a transmission: the one I posted before turned out to be a scammer and wasn’t any good. I ended up with another RSX Type-S 6-speed with a Z3 LSD and new syncros. From what the seller said it came from Shawn K20 — I didn’t know who he was, but he has a following on Insta. The seller just never got around to using it. I also got K-Tuned cables.

A couple things I’ve decided: I’m going to go with new rods and pistons. Since I’m replacing piston rings and bearings, might as well replace everything, right? (My wallet is crying.) I’m looking at Nippon Racing turbo pistons and SCAT rods. I’ll still run 87 mm — the walls are good but need a proper clean. I also picked up a 4-piston oil pump with the K24 install kit for a good price.

Now the questions — and anyone is more than welcome to add input, ask questions, or tell me to shut up. I’m very open and enjoy the conversation and learning.

From what I’ve read and been told, the transmission and power goals are still going to be an issue: unless I upgrade gears, I’m not going to be able to put this power down without breaking something or just spinning all the time. So — is it worth upgrading rods and pistons without a gear upgrade? Current pistons are fine and just need some loving, or should I do the new rods/pistons now to be safe and avoid sending a rod into orbit later?

About the 4-piston oil pump: I called 4-Piston and asked about oil pans. They said most pans work but pointed me toward what they offer, like their 4P race pan and Moroso pan with baffles — but those are extremely expensive ($500–$800). I’ve seen conversations here about other options like Unit2Fab but couldn’t find what would work with the 4-piston pump without spending a fortune. I understand the reasoning behind the prices, but I’m wondering if there’s a budget option or a DIY route that would work.

Using Lotus and other posts from a while back to find comp ratios, I came to ~10.4:1 with the pistons and rods I mentioned and a stock-sized head gasket on E85. Should I shoot for a lower ratio and change to a thicker head gasket to bring comp down? I’ve also read that in this turbo application a slightly higher comp (10.4 vs something like 9.8) can help with E85 and "longevity" but need a good tune — so I’m on the fence.

Don’t be afraid to tell me what you think or what I should do — very open to opinions. I still have a lot to buy and do to get this thing running, or I could just slap it together, run it NA, and see what happens from there.

Cheers — thanks again for all the help and for taking the time to read. Truly the best car community in and out of the forums.

 

10.5 CR is good for any boost a stock gearbox can take even on 93 octane gas.
e85 runs great on a turbo. Just use a OEM headgasket. Thicker ones reduce squish, something you don’t want if you can avoid it.
if you rebore the block, I‘d go for Mahle 4032 alloy pistons. If not, the Nippon pistons will be gone for some 400HP as well. both will last much longer than 2618 alloy pistons, will clapper less and use less oil.
if this is a street build and you got a PRB k20a2 style oil pump, why not just get a k20a2 oil pan and a baffle kit?
Doing a swap and a turbo build is already complex. I’d keep it as simple as possible on the engine and gearbox side and get it to run properly, heat managed well, 2.75” to 3” drone free exhaust etc. running for a season.
Then build an engine and a gearbox if that power you got is not enough. This is unless you start to track the car.