The plan is to upgrade to some type-s pistons... I checked the back of the block and it reads BBBB so that tells me i need size B pistons. The question I have is after the hone do I have anything to worry about with the hone being larger and out of fitment for the the size B type-s pistons?

 

Depends on the condition of the cylinder. It could be worn badly to the point that it needs .010" taken out to get the cylinder round and straight again. Then again, it may only need less than .001". Your best bet is to take it to the machinist, see where it cleans up at, and choose a piston size based on that.

 

To add to the question, since a set of mahle pistons are relativly the same price would cylinder size matter since they only come in one std size at 87mm?

 

Of course cylinder size matters. Isn't standard bore size already 87mm? I see Mahle 87mm and 87.25mm pistons. If the hone takes out too much material to clean up to use the 87mm pistons, then you will need to use the 87.25mm piston and hone the block to to the right diameter to get the proper piston-wall clearance.

 

There is no need to hone the block unless there are deep vertical scratches - there is an article from Honda floating around here that says not to hone the cylinders unless the condition permits . If there are, send the block to someone who knows how to machine FRM, there are special stones used and a special procedure to do so. IF that was the case, especially since you're already at the B size, the machinist should hone it out to use the 87.25 oversize pistons.

 

First of all, you don't "overbore" .25mm of material, that's the thickness of a couple sheets of paper. You only need to hone that out.

Second, I saw that same service bulletin (VSB618958 #18939) and the process is no different than honing any other block, except that you use stones for a non-ferrous metal, and finish up with a smoother finish. If you are ok with the cylinders being tapered and out of round, and just popping in pistons at who-knows-what piston-wall clearance, by all means do it. However, if you want a round, straight cylinder and set the piston-wall clearance correctly, torque plate hone the cylinders. It will seal better, consume less oil, make more power, and the rings will last longer.

 

I find it disturbing that nobody informed you that the BBBB on the back of the block has nothing to do with your pistons. Those markings refer to the sizing of the mains in your block.

 

LOL, beat me to it.

 

there are two different sized pistons for the h22. an A and B. It should be on the top of the block.

https://honda-tech.com/forums/honda-prelude-4/how-have-frm-honed-2476019/

 

Agreed and I'll also add that bulletin is for a stock engine not a performance build so it does not apply. The stones you use to hone will have more to do with the piston ring material you choose. Do it right and use oversize pistons so you make sure those cylinders are straight and round. Plus the increase in bore size will give you at least an extra 1/2 HP.

 

Very interesting...

 

If I am reading correctly the proccess of going to a .25 OS is done through honeing and not boreing the cylinder out? If thats the case id feel much more comfortable just going with an OS piston.

 

Semantics, sorry. I fixed it. I certainly won't argue the best way to do it is to get it honed properly and have everything straightened out. It just seems there have been a few too many stories around here of people's blocks getting messed up because the machinist didn't know what they were doing.

 

Thanks for the info.
That's weird and cool. 0.0004" difference in diameter between the A and B pistons... crazy FRM motors

 

Just to put it into perspective, 1mm is about .0394 of an inch (thinner than a dime) so a .25mm is less than .010 of an inch. When you bore it, you are supposed to leave .002-.005 of an inch to hone for a proper surface finish. I just pulled a sheet of paper out of my printer, measured it and it is .005 of an inch. You would almost need a very expensive CNC machine to be able to bore something like that accurately.

 

The only advantage to using a boring tool before honing that small an amount is to ensure that the cylinders are exactly perpendicular to the plane of the crankshaft main bearings. A hone will follow the existing cylinder. Most machine shops will just hone it.