How far can a b18a1 be safely bored out to in millimeters without being sleeved? Just to run N/A. Thanks guys

82.5mm would be the most i'd go. maybe 83mm if the block is that messed up. any more and the block is junk

82mm would be the most without sleeving. CP's 83mm forged pistons are meant for sleeved blocks.

i dont think your supposed to bore them any more then 20 thou

I wouldn't go any larger than 82/82.5.

the largest i have seen without sleeves is 83mm but with sleeves u can go up to 86mm

Possible to bored it to a 84mm?since it is suppose it ly the same block as the b20

84 I doubt would be possible. 82.5 would be the highest I went with to be on the safer side.

The blocks are similar but not the same. The wall design of the cylinders are very different. I know it's painful to think about having to buy a new block, but i wouldn't be boring more than 20 over. Buying a new head gasket (~$100), Machine work (~$250-$300), time (how much do you make an hour compared to how much are you spending on a pain in the A project), not to mention having to buy new rings, and pistons to match, and then getting it tuned again to componsate for the changes you've made = Think long and hard about what you're doing or what you're going to do and read this and other forums a million times over. I'm not sure if that made any sense to you, but I hope it helped.