Honda Prelude Forum banner

1 - 5 of 5 Posts

·
Registered
1999 Prelude. F20B/K20A hybrid rebuild
Joined
·
175 Posts
Discussion Starter · #1 · (Edited)
Hi Yall, so long story short, on New Years Eve my stock H22a4 blew up and melted a piston on me. She ran strong for 242,000 miles original to the car.
29100
29101
Well some things happen for a reason, the previous summer, i actually purchased a used F20B that had a blown piston from being boosted by previous owner. I bought because i knew F20B’s have iron cylinder walls and that would make it easy to get bored out for bigger pistons and a rebuild.
29094
29095


Well i had taken it apart and it was as i expected besides the crankshaft main journals having slight scarring.

So i had the machine shop bore and hone out the cylinders 1mm over. And had them slightly grind and polish my crankshaft to fix the damage.
29096


So i was stuck with a couple different options for pistons, i knew this was gonna be a Naturally Aspirated bolt-on type rebuild so it was between finding OEM F20B 1mm over-sized pistons which would’ve been easily $400-500 (because they’re JDM imported) which is the same price of FORGED pistons. OR, after doing TONS of research.. i decided to to JDM K20A Type R pistons. They are 86mm stock which is the perfect size since my F20b was bored from stock 85mm to 86mm. I purchased the K20A pistons before i dropped everything off at the machine shop and i had them match the block to the pistons with spec-ing the proper Piston-to-Wall clearance for the K20A pistons. They were Nippon-Racing brand and were only $240!! Rings included and free shipping from SwapShopRacing.com
29098
29099


Now, a lot of people argue how K20 pistons LOWER compression in a F20B block, which is true because K series pistons are 1mm shorter than F20b pistons which does lower compression. BUT, most people assume that thinking about USDM k20 Rsx type S or civic Si pistons. Those usdm K20 pistons are not the same as JDM Type R K20A. The Jdm K20A pistons are much higher compression than the usdm versions, a usdm k20z type S might push 10.5-11:1 compression ratio, where the Jdm K20A type R pushes about 11.5-12:1 in a K series. So yes, they are still 1mm shorter, but having my block and head slightly decked, and considering the higher specs of the Jdm Type R pistons, my F20B will still be pushing anywhere from 11-11.5:1 compression ratio, stock is 11:1. By the way, i wasn’t aiming for super high compression, the K20A pistons were the CHEAPEST option!

SO, a month or two after the machine shop and everything was ready. I had all my oversized bearings, brand new OEM Honda oil pump and seals genuine. New Oem main bolts and Rod bolts. Everything i needed to make it perfect.
29104


After some time working magic in the garage and being very OCD about everything like checking clearances and proper torque-ing. It was assembled, and shortly after i swapped it into my 5th gen.
29105
29106


I ended up doing a proper break-in/seating of the piston rings for about 60-100 miles doing various 1/4 throttle pulls and a lot of engine braking.
I changed the oil to full synthetic after that, and she was fully ready!! So far it’s been about 3 months running, already have about 4,000 miles on the F20B and it’s running like a dream!! Pulls great, real responsive, and LOVES to revv high! And after a couple races is almost DEAD EVEN with S2K’s(i’ve raced 3 different one’s) This is my FIRST ever engine rebuild so i’m super satisfied with how it turned out. Thanks to my proper breaking-in of the piston rings i haven’t even burned a DROP of oil on any of my oil changed so far, which i could not say about my H22 LOL. *i also went with K20 piston ring gaps and windowed all the rings using K20 window directions.
All in all this was a great experience for a first-timer, i gained a lot of knowledge and i’m hoping i can use it in the future for much cooler and more serious builds. If you made it this far, thanks for reading!!
 

·
Registered
Joined
·
4 Posts
Very nice build sir and great job! I'm in the process of a build myself. Good to see other do-it-yourselfers be successful in their builds. I'm currently working on a G23. I have a h23 jdm blue top head on a f23 shortblock with k20 type s pistons. It's all pit together and ready to go back in my lude. I'm still trying to figure out what tuning/ecu to go with tho. What is your's tuned with? And are you running regular premium gas?
 

·
Registered
1999 Prelude. F20B/K20A hybrid rebuild
Joined
·
175 Posts
Discussion Starter · #3 · (Edited)
Very nice build sir and great job! I'm in the process of a build myself. Good to see other do-it-yourselfers be successful in their builds. I'm currently working on a G23. I have a h23 jdm blue top head on a f23 shortblock with k20 type s pistons. It's all pit together and ready to go back in my lude. I'm still trying to figure out what tuning/ecu to go with tho. What is your's tuned with? And are you running regular premium gas?
Nice! Those G23’s are perfect for K series pistons especially because they are already the perfect height on the rods so you get the benefit of higher compression. But yeah! i did forget that info in my post.. so basically i’m using my 5th gens h22 full stock harness, hardware, and sensors. From the stock H22 i swapped over the entire intake manifold with injectors, distributor, and knock sensor. Also i bought a brand new H22a4 oil pump which has mounting for the crank sensors(Jdm’s don’t). And also swapped over the h22a4 timing and balance shaft gears. So with all that stuff on the F20b my 5th gen is running it with full stock Ecu and harness and i didn’t need to do anything crazy. No Cel’s either. I also have a adjustable FPR so i set the fuel’s psi on the lowest of OEM spec(30psi idle) i did that so it doesn’t run super rich since it thinks it’s a 2.2. With that being said, yes since it’s on stock Ecu so i know it’s not full potential yet. It runs smooth, efficient, and powerful enough where i don’t mind it. But i know if it was fully tuned i could potentially gain 20+ HP, i have tuning plans for the future and mods to go with it, i have a fully ported intake manifold and a 70mm TB, also a PLM Try-Y header, all would be installed before the tune. But right now based on all the races i’ve done and how it feels it’s probably pushing 190whp, with how dead-even it is with S2K’s that sounds about right(they don’t even pass me until 90-100mph). I think a tune with those mods above could get me to over 200-220whp, anything above 200wheel i would be very happy. And also yes i’ve been running Premium gas in my area it’s 93 octane
 

·
Registered
1999 Prelude. F20B/K20A hybrid rebuild
Joined
·
175 Posts
Discussion Starter · #4 ·
Also important F20B rebuild info:
Main bearings:H22a4
Rod Bearings: B16A
Main bolts: H22a4
Rod Bolts: F23a *Torque- 20ft-lbs + 90 degrees after.
Headgasket: H22a4
ALL SEALS, GASKETS + O-RINGS: H22a4 (97-01 Prelude reference)
 
1 - 5 of 5 Posts
Top