TODAEG9

Hi everyone,

i am planning to have a rebuild my JDM 2004 AP1 Facelifted F20C,

From the beginning i decided to buy Mahle FRM piston 12.5CR 87.25mm with Carillo Pro A F22 Rod,

but after a discussion with my local machine shop, seems they dont have any confidence even i gave him the guideline for bored and honed block from original manual.

So now i am started to think about keep my JDM AP1 piston to avoid any pison failure if they are good enough to re used, just change new rings from 06+ AP2, seems they are a better design isnt it?

And swap in the Balanced and Micropolished F22C Crannk and F22C original rod, since i used stock piston with 22.7mm pin diameter so this is a direct bolt on without any machine work, and they are floating rod and good enough already for 250~ whp. Just a little bit heavier than Carrillo Pro A.

I had do a research for AP2 Rod + Crank plus JDM F20C piston = 12.7 CR ! Am i right? seems its a beast for All Motor setup and even higher CR than Mahle piston.

Finally i found that is no point to buy after market parts, and i heard S2000 OEM piston is forged already.

Any comment ? anyone tried this combo before?

Thanks!

chris_barry

I would use the AP1 length rod along with the Mahle piston with the shorter compression height. This improves the rod/stroke ratio for safer higher rpm. The Mahle piston also has 12.5 compression.

If your machine shop is not OK doing FRM bores, find one who can do.

What you suggest will work if you are on a budget. You just loose the opportunity to correct the bore wear that most used blocks have.

Check that your factory rod little ends/pins are not gaulled. Most used motors I've pulled apart are showing distress in this area.

TODAEG9

I am located in Hong Kong, the best machine shop already is the one i had taught to, the others one even tell me dont know what is FRM.

So i think to do FRM bored and honed in my local area is no hope, only shipped overseas to do but shipping is in sky high.

I had think about the long rod option also but seems i will lose some low end torque. So finally i leave it, and the main problem is i cant change to aftermarket piston in my case. My JDM F20C have 84000km , i dont know how it looks like inside but the engine still in good health, good response and no oil burning.
I hope my piston wall is good and piston can be re used.

Can anyone tell me whats the different from AP1 to 06+ AP2 rings? i found someone said its better design but i dont know whats the different.

I am planning to order new rod from Honda Japan, quoting the price now or maybe i can purchase used one at web.

wadzii

the machine shop should contact the company that makes their honing machine to get the right stones. Any bore/hone machine can do frm, the process isnt different, it only takes a different stone.

the later ap2 rings have a napier hook on the 2nd ring.

no matter the piston you still need to hone the block. Boring an f20c block is exactly the same process as any other block, only honing takes a different stone.

TODAEG9

I will try to figure it out with the machine shop..

But if i keep the old piston still need to honed the block?

Seems every honing process will make the bore a little bit bigger?

If i use stock old piston, honed the block then = bigger P-W clearance?

And i did a research seems freshly honed FRM cyc suppose shine like a mirror, not like the normal one. Right?

thanks!

Andrew17930

i just had my f20c block bored over .25 from my machine shop that never done a frm and it came out great with no issue and i got the mahle piston 12.5CR 87.25mm with Carillo Pro A rods. still waiting for vale springs to come in!

TODAEG9

Did they say any about the boning stone?

Andrew17930

yes they had to get stones made for frm blocks and i got valve guides put in to and it only cost me $250 for all of it!