AP2 nominal bore size
 

Hi guys, do you have any idea what the bore size is of a brand new AP2 block? I am trying to find out if the F22 has the same piston to wall clearance and the same nominal bore size new as the F20, as i am looking to install the newer pistons/rings that eliminate oil consmption issues but i can't find anything, and i can't find a service manual too for the 04-05 model (i already have the 2000-2003 service manual)

Bore sizes are the same, BUT both AP1s and AP2's technically have 2 different size "Standard" bores. The block will be stamped on the head surface with "BBBB, or AAAA, or ABAB" or any combination in between. The pistons are also stamped in the very center of the dome with a corresponding letter. Pistons with NO stamp at all are "A" pistons, and ALL "B" pistons will have a stamp. You CAN use AP1 pistons in an AP2 block and vise versa, as long as you pay attention to those bore codes. :thumbup:

This is a great post, very clear and informative.
Regarding the AP1 vs AP2 pistons rings, do you know if they are interchangeable? I mean i don't see why not since i read in another thread that they have the same thickness and the bore is the same, but on the other hand i can't be sure if i don't have an Ap1 and Ap2 piston in hand to measure the ring channel dimensions, and if i could get away with only replacing the pistons rings with the improved ones, that would a great money saving, as long as it's technically 100% correct!

I would use AP2 piston rings regardless. They are a better design and an improvement over the AP1 rings. (of which there are 2 different part numbers for)

Good luck and glad I could help. :tipwink:

As long as the ring gap, groove clearance, etc are all to specs I don't see why you can't use AP2 rings in AP1 pistons

To add to Jordan's post, no letter or A pistons have a diameter of 87.993mm to 88.006mm and have a service limit of 86.980mm.
B pistons have a diameter of 86.983 to 86.996 and a service limit of 86.970mm.

Pistons are measured at the skirt, near the bottom of the pin because the top of the piston expands more.

A or 'no mark' pistons are matched to bores that are between 87.01 and 87.02mm
B pistons are matched to bores that are between 87.000 and 87.010mm
With service limit @ 87.07mm for the cylinder bores.
for ships and giggles, oversize bores is 87.25mm to 87.26mm, which would make the displacement 2012.7cc assuming 84.4mm stroke for AP1.

Piston to cylinder clearance is from .0002" to .002" or .004 to .04mm.

Ring to groove gap is .045-.09mm with service limit of .135mm for top ring, .040 - .07mm for bottom ring with service limit of .13mm clearance
Ring gap is .30mm +- .05mm for top ring with .60mm service limit
2nd ring is .60-.75mm with .9mm service limit
.20-.70mm with .90mm service limit for the oil control rings.

And all of this is EXACTLY why any shop attempting to rebuild this motor that is not familiar with it will 99% of the time F up and cost you more money or even your engine. Period.

I've gotten engines shipped to me for (re)building that had just been rebuilt and I found A pistons in B cylinders and vise versa, a bunch of mix matched bearings, non OEM gaskets, etc. And then people wonder why their engine failed.

Plain and simple, if the shop you're going to doesn't have a track record of successful S2000 engine (re)builds, don't let your engine be their guinea pig. Because that's exactly what it'll end up being.

I am doing all the work on my own, and i am always taking great care in the little details and double measure everything. I knew already the bearings sizing method, i knew the difference in size between pistons A and B, but i didn't know that pistons A and B could live together in the same block. The question is, are all these dimensions and gaps/clearances the same with a late (04+) EU F20C2 and an US F22C1? That's the reason i asked if there is a manual for the 04-05 or 04-09 S2ks

To add something on the topic, the EU 04+ F20C2 uses the same part number piston rings as the US F22C1, the piston itself is a different part number, obviously for the shake of increased capacity, less dome volume to bring the compression ratio down.

By the way, the reason i want to rebuild my 00 AP1 is because it consumes 1 quart of oil every 1500 miles on mild daily use and occasional,short, high rpm runs. It will smell burning oil sometimes when stationary idling in traffic and then taking off, or blow a small white cloud from the exhaust when i shift near/on the rev limiter which i notice throuth the mirror. I am not worried about changing the piston rings and valve stem seals, but more finding a scored cylinder wall

a lot of your information doesn't match up with the service manual.


OP ignore the post above and go by this (from my 2000-2007 service manual):
Attachment 178170
Attachment 178171
Attachment 178172

Another great post, keep it coming, this can be of great help for those looking to do a rebuild, and we can finally conclude if we can all use the 04+ F20C2/F22C1 piston rings on the earlier AP1 pistons to fix or improve the oil consumption issue. Honda changed pistons and piston rings three times in 5 years, this is not incidental.

Although there is a part number that has replaced all the earlier version AP1 piston rings (13011-PCX-305), and i am wondering if there is any improvement on that or they just did it so they don't have to stock so many different part numbers

Umm all the numbers I posted are exactly the same as yours, sooooo I don't know what the big deal is. I know I have a funky way of writing it but trust me they're the same if you check. But thank you for including the diameter of oversized pistons, my dyslexia gets the best of me at times.

After reading your manual I actually spotted a typo, the service limit for piston to cylinder clearance is incorrectly stated as .004mm, where that number should be .04, .004 is the smallest the clearance can be.