Hey whats up guys the 98 accord is on its last leg and im ready to tear it down and freshen it up i wanna do a nice street build but cash is kinda low so i decided since the k20 pistons fit the f23a1 block and rods then maybe i can get a slight AM build going for stupid cheap my concerns are as follows 1. what compression will i be expecting using the stock f23a1 head 2. will it be best to port the head 3. any special advice needed to install these pistons 4. has anyone done this piston swap without the h22 head

 

depends on which K20 pistons you use

zealautowerks

check the link and play around with different combos for an idea of static comp ratios. i can tell you from checking it out myself that K20A3 (RSX base) will get you about 11.0:1 and K20A2 (RSX type-S) will be just above 12.3:1.

you will need to "run the backwards" or rotated 180° to account for the pin offset. i've checked K20A3 piston/F23 bottom end/F22A head for piston to valve clearance and there is no issue, but with the higher dome of the A2's (and possibly different valve angle in the F23 head?) i would check for clearance and expect to modify if needed.

 

Thanks ur a big help and the site is the ish also so ur saying go with k20a3 pistons for safer build and still be able to daily drive...and im using my stock f23a1 head and maybe buy a bisi cam later so tell me more bout the way they get mounted inside of the block and the wrist pin offset?

 

i believe either compression ratio can be 'safe' since this is the static not the dynamic comp ratio. (there are some terribly good, in-depth threads and articles out there if you need a better understanding of the difference. i'll humbly refrain from trying to explain what i don't fully understand, but encourage you to run a Google search.)

compression should be the same with the F23 head as it is with the F22A head.

not to pick on you.. i wouldn't call it mounting them in the block, rather installing them. i have a thing about word usage, sorry . the offset of the wrist pin helps reduce wear by lessening side load and piston rocking during the power stroke. because the two motors -- K-series/F-series -- spin CW and CCW respectively the direction of offset is opposite (towards the intake side in the K-series and towards the exhaust in the F-series).

so, if you are using pistons from a CW motor in a CCW motor you need to put the intake side (the direction of offset) of the piston on the exhaust side. rotate 180º. checking piston to valve clearance is the only other extra step compared to a stock F23 piston install.

 

Is the f23a bore size the exact same as a k20? Meaning the k20 pistons drop in without a rebore granted your cylinder walls look good.?

 

Yup, both are 86mm. You will need to verify you won't need an overbore to clean up the cylinder.

 

What about the stroke? And the rod length? And the distance from the wrist pin to the top surface of the piston? And the placement of the notches for the valves? All compatible?

 

The K20 pistons work fine with stock rod length, stroke, etc of the F23. They must be installed backwards to compensate for the difference in wrist pin offset of the two engines. This may pose an issue with valve reliefs if a big cam is used but under typical circumstances it's not a problem.

You can get varying different kinds of K20 pistons with different compression ratios. It would be beneficial to go to www.zealautowerks.com and use their compression calculator to figure out your static compression with the pistons you plan on using.

 

I am kind of surprised that it would work out that well. Good info.

 

called compression height, same for both.

with installed "reverse" to account for wrist pin offset there is plenty of piston to valve clearance with a Delta 272 (higher lift) cam.