Boring FRM Sleeves

[thumping_accord]

So I've done some searching and I don't know if I'm being completely ignorant about this subject or what, but I keep finding conflicting info about this subject.

The H23a1, that i just rebuilt about a year ago, is in need of piston rings already. I've talked to my machine shop about the problems I've been having, basically too much pressure in the block, and they said the rings are the cause of my problems. At this point he said that they shouldnt have gone bad so fast unless something was wrong with the cylinders, such as if they were not straight, he then said that to fix the situation the block would have to bored over 1/10,000. which I believe he said would be .2mm.

So I've been researching because I was under the assumption that FRM sleeves couldnt be bored and the only option was resleeving; however, during my searching I found that someone bored there FRM sleeves .25mm.

My big question can I do the boring and be ok without having to resleeve? Has anyone bored there FRM's? What kind of problems were there if there was any?

[Joey GT-R]

FRM sleeves can be bored and are bored often. The issue is finding a machinist that has the capability of doing so as it is not a straightforward process as traditional blocks. You need to find a shop that is familiar. Porsche uses FRM in their 911s so if you know of a shop that specializes in Porsches they will know exactly what you're talking about.

HondaTuning details the process here.

[Stoner51]

They can be bored but only so much. How much I don't know?
I am using more oil than I would like. However I have a rear main seal leaking so I'm thinking king it is that but I have been reading some as well.
The general concensus that I read says you just replace the rings usually. Did you use oem rings or another brand?

If I were to do my swap now I would go f20b. Iron sleeves no trouble finding a special machine shop.

I have no experience with this just what I found on my research

Steve

[thumping_accord]

thanks for the quick responses, ill need to check if my machine shop will be able to do it or not, but by the sounds of it more thank likely I will have to find another shop.

[illinois_erik]

which rings did you use as replacements? the reason why the rings went bad is because the FRM is harder than the metal the rings are made from. if you can inspect the bore of the cylinder and its not scored leave them alone. measure to make sure theyre not tapered of course, but FRM is pretty resilient. try OEM rings or FRM compatible aftermarket. Or talk to a machine shop that has FRM experience because regular cylinder wall knowledge must be dropped when dealing with FRM. example, you dont use the dingleberry hones in them or even stone hones. Theres a specific procedure that finishes up with buffing the cylinder walls with silicone paste and felt pads like on a regular stone honing tool. just my 2cents save money where you can.