going through the overhaul procedure for my B18C, I found this statement in the Honda Manual:

". lf measurements in any cylinder are beyond
Oversize Bore Service Limit, replace the block."

Oversize Bore Service Limit:
81.25mm

SO, HONDA recommends a max over bore of just 0.25mm, or your block is no good!!! I've looked in a 95 manual and a 00 manual, both had the same spec. also, there are only honda replacement parts for standard and 0.25mm over.

I know people have been over-boring higher than this, so what's going on? can anyone comment on this spec?

 

Honda/Acura only sells one oversize (+.25mm/.010").Generally a 1mm (.040") is the max on stock sleeves.

 

you can do 81.5mm no problem. get the pistons, have it bored and honed to the right size, and assemble.

 

so all these aftermarket pistons that are out there are for aftermarket sleeves?

somehow, i find it hard to believe that all these kids are running around with oversized replacement sleeves.

sounds scary. what's actually out there, i mean. now all the stories about dropped sleeves and busted head gaskets are starting to make sense...

I realize, i can go larger than the spec, but since i am running boost, on a stock block, i need to be careful. now finding this piece of info makes it even more critical that i get something that is stock bore.

what kind of success have you seen with 81.5mm?? have you actually run this number or is it based on what you have heard out there?

and why do you say 81.5? why not 82?

please share any experiences you have had. much appreciated.

 

81.5mm b16a stock sleeves, i made 463whp on it, pulled it, sold it, and its in a street car making 460whp, still running strong.

 

I think the price of the piston increases, along with the bore diameter.

EX: 82, 83, 84mm pistons will cost more than 81.5mm

some folks can only afford to go with stock sleeves that have been bored to 81.5mm and use 81.5mm pistons, rather than 82 83 or 84. on top of that, most folks who run sleeved blocks will usually be running a bore diameter bigger than 81.5mm.

i have a friend who bored out his b18c1 block to 81.5mm and is running eagle rods and cp 81.5mm pistons and its running perfectly fine.

 

actually the cost of forged pistons 81-85mm are all pretty much the same price.

81-82mm max on stock B16/B18 sleeves and you will be fine.

84-84.5mm on stock sleeve B20 is fine with proper tuning.

 

fine, with what else? a block gaurd? arp studs? when it is not fine, what breaks? what is the failure mode?

how many miles is it good to? 20k, then what? you blow a head gasket?

honda had a specification in mind when it set the 81.25 limit, after that a design parameter is exceeded and something breaks. maybe not today, maybe not tomorrow, but something will break. someone will say they are trying to make more money, i doubt that.

obviously i do not want to get into a long winded discussion here. just wondering if there is someone knowledgeable enough to speak on the subject of design limits and failure points of the B-series.

 

most honda acura performance shops are building 81.5 82 83 and probably even 84mm b series blocks, that are capable of handling high horsepower, granted you probably dont see these cars on the street often, more on the track.

on top of that, most of those high hp b series setups are running SLEEVED BLOCKS. Blocks that have been sleeved by Golden Eagle, Darton, and other engine sleeve manufacturers

id say you would have no problem building a 81.5mm b series block, as long as its BUILT RIGHT and of coursed TUNED properly....

 

81.5mm stock sleeves is fine!!!!!! they will hold up just fine, detonation is the enemy. the head gasket wont magically blow because of the .5mm overbore. measure a stock headgasket, they are bigger than 81mm anyways.