Hey, as you gathered from the title I'm doing a build with an F23 block using K24 pistons and H22 Head since i have some **** lying around. Also i know that K20 pistons are the same bore as the f23 and the reason why I'm not using them is because one of the cylinders is out .020" so I'm gonna have to overbore anyway.

Basically my question is which K24 pistons should I use? There are many models of this engine with different compressions and also when you look it up on honda parts sites you get piston set A and B but it doesn't say the difference!!

I'm no Newb to building engines but I'm just getting into in debth honda motor building as my last one was with a turbo mazdaspeed protege 2.0L with forged internals and it's very different with honda on an N/A build haha.

Anyway any advice on this would be great :D

 

87mm bore prelude psitons will do the trick no problem...BUT I recommend you cc out the cylinder head and do some other various measurements to get your CR on the money...altogether stay away from K pistons(they are not meant to mov CCW)

my .02 cents

 

K24 pistons out of the new accords will work the best. You'll be looking around 11.0:1 vurses 10.0:1 w/ the tsx pistons. As far as A and B pistons it doesn't matter as long as you get all the same. All B pistons or all A pistons.

 

In layman's terms what he is saying is that the K24/K20 OEM cast pistons have a wrist pin offsets that works in conjunction with the Clockwise direction of the K24/K20 rotating assembly. Where as the F23 has a counter clockwise direction rotating assembly.

It's more reliable to have custom forged pistons made for your particular hybrid engine build. Your not the first to do a G23 VTEC build. There are probably a few shops that have piston specs ready to go for these builds. Give the chaps at Race Engineering a call and see if they might have a kit that will suit your needs and budget. They helped me out with my internals, great bunch of guys to deal with. Contact them via raceeng.com

Does anyone have an G23 hybrid running K24/K20 pistons with any mileage on them yet? I would like to see one torn down and see how reliable the OEM cast pistons are in the F23 Cylinders. I have also heard that Wiseco forged K24/K20 pistons don't have a wrist pin offset.....How reliable is this information? I would figure if you are making a piston for a particular engine that you would stick to what works with the OEM parts as per offsets and compression heights???????

 

My Wiseco's do NOT have a pin offset.

 

I'm out of a job and waiting to get a TP sensor from a friend to get the car running. This is all that's needed before its up and running. As soon as I can get a job and tuned with some miles on it will let you know.

 

Yeah I have heard a little talk about that pin offset on K series and that you have to reverse the piston and mill the former intake side of the piston to clear the exhaust valves. Sounds like a little bit of bull to me because it's still offset just the other way lol.

Then again if the forged pistons for K series don't have an offset than how much of a difference can it really make if wiseco decided to **** the whole idea of offsetting it.

I just looked it up and I can get Wiseco pistons with 11.1:1, 12.5:1 or 13.7:1 compression for $500 and it comes with rings, pins and locks. OEM K24 piston sets from the new accords are $180 for 4 plus $130 for rings. This is 10.5:1 I believe for the 08 models. Also the 09 TSX has 11:1.

So $310 for oem cast pistons which have an offset that may or may not be bad or $500 for sweet Forged pistons that are a bit lighter and will NEVER break.

HMMMMM..........................

 

Forged is definatley the way to go if your wallet permits! Just be sure to check all clearances, especially if running high lift cams.

 

Clearances aren't so much an issue as the K series pistons almost mirrors F series for everything even the valve reliefs. If I used say H22 pistons then I'd have to mill the head to fit them.

http://www.blueprintracing.com/upima...wiseco_125.jpg

Those just look too sweet I think I'm in love

What compression do you guys think i should go with?

 

Better safe than sorry... I have clayed this setup with different cams and you would be suprised at just how close P2V is. Yes, the pistons are similar but the K and F series are two still two different breeds. Remember - valve angle also plays an important role.

 

cc the chambers, add HG thickness, and pick the CR...it's simple

H22 87mm forged pistons @ 11.5-12.0 dynamic CR and 2300cc's of volume will net you good results with Pro2's...

 

I'm really racking my brain on this one. I've been all over the internet for 3 hours trying to get figures and information but I can't seem to get exactly what i need.

Mostly that one site says h22A head on stock f23 block will produce 8.8:1 CR which is .5 below stock. But then somewhere else says K20A pistons which are usually 11.7 or 11.5 will make the compression ratio 11.5:1. which I don't really understand but kind of do thinking of the k20 peaked piston design. But i really wanted to get all the figures and calculate it myself before i blow $500 on pistons and find they don't fit. But it's really scarce to find the info on this for some reason.

It would be find if i had them lying around and could just try it, but I can't just rent them for a day you know.

According to what I've read if I get 11.5:1 k20 pistons oversized to 87mm then I should get roughly the same compression in my g23. Offset ins't an issue as I'm going with wiseco pistons. Does this make sense?? My head hurts from all this reading.

 

ok so I FINALLY have figured it out. Used this website http://www.zealautowerks.com/hfseries.html and I got information from a k20-24 estimator on the same site the specs of pistons to plug into the thing.

I found that with H22 head on f23 block with f23 rods (Changed bore to 87mm) and K24a4 pistons (0cc dome displacement, 30mm comp height) and a stock head gasket I was getting around 11.7:1 which isn't bad at all. Worst case scenario I could always get a thicker head gasket if my compression was too high.

Does this information seem right? I'm still having a hell of a time wrapping my head around this frankenstein ****. I'm just starting to get how 9.7:1 pistons in one motor can make 11.7:1 in another haha. I hope this calculator is accurate!!!!!!

 

Your close. F23 block, crank and rods with a Flat Top K24 piston @ 0cc & 30mm compression height (same as the F23) with an H22 head w/54cc combustion chambers (F23 has 50cc chambers) your looking at approx. 11:1 CR.

 

import tuner has a real informative article on this subject. Feb 09 issue #119

 

Import tuner's article was based on jdm_ef9 build anyways. So just type in "jdm_ef9" and look for his build under search. Save time and definitely money from buying those magazine filled with spam.

 

Yeah I've seen that article, it's informative but they did leave out a couple of key details. But I think I've got it all figured out now. I have a Full F23 vtech thats in good condition and an H22 longblock with a blown bottom end. I'm just getting started on stripping them down and starting little things like removing and milling out the butterflies and EGR on the h22 intake and other things.

From what I've seen the H block and crank isn't too bad of shape. The girdle and oil pan got ****ed but the cylinder walls are decent. Good stuff to know if I ever needed to use it, just needs a hone. Maybe put the f23 sohc head on the h block lol.

Thanks for all the info guys! Made the transition into Honda engines a little easier. Frank motors hurt my brain at first haha.

 

So, what do you guys suggest if I wanted; say 10.5:1 compression on an F23A1 VTEC, not a G23 (Frankenstein) H head swap - just your plain F23 block & head. Thanks!

 

Sweep the leg, err. I mean mill the head.

 

Forged pistons are the way to go, as mentioned earlier: stonger, and more reliable toward abuse.

 

I'm sure theres a MILLION threads that already answer this question. Find the F23 THREAD!!!!!!!!!!!!!!!! not the G23 HYBRID THREAD!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Posting here makes NO SENSE AT ALL.

 

I did... typed F23 on the search under "All Motor"; this comes up!

Anyways, I'm interested in increasing compression using K20/k24 pistons but have not found anyone using an F23 head, only hybrids... yes.

Not trying to bust your thread, just clarify compression differences between F/H heads since everyone seems interested in using K-series pistons on the F23.

 

K20A2 = 86mm bore, 30mm Compression height with a 4.25cc dome piston in a 50.5cc head = 11.5:1CR
K24A2 = 87mm bore, 30mm Compression height with a -3.1cc dish piston in a 50.5cc head = 10.5:1CR
F23A1 = 86mm bore, 31mm compression height with a -14cc dish piston in a 50cc head = 9.3:1CR
(if anyone physically knows the measurements please correct, these are complements of the interwebs)

If you go buy the numbers found on the interwebs and do the math this is what you would get in an F23A1 wF23A1 head
K20A2 piston = 12.4:1
K24A2 piston = 11:1
Calculations courtesy of zealautowerks.com Honda compression calculator

But the only real way to measure the compression is to physically cc the head and piston. Then clay the engine to ensure that the valves don't smack the pistons or the pistons don't smack the head. (with a 1mm shorter CH I don't think piston to head contact should be a problem)

 

Piston to head is not a problem. The F22a head has the same cc's in the head bowl. When I measured there was no problem with piston to head contact. I measured with no head gasket.

If the valve reliefs are cut correctly there's no problem with valve to piston contact on stock sized valves, not sure about over sized. You can take quite a bit of material off the pistons them self's to make room for the valves.

 

Thanks Ghost... great info. At least it tells me the K24A2 is worth trying.