I have a B18C1 that needs bored out. I noticed that most of the overbored pistons you can get are .020" over. Does that mean I need to have the block bored out .020" over stock or do I need to have it bored out more to allow for the ring clearance?

 

it depends how bad the walls are if there not bad then a .10(81.25) over will do but you might have to do a .20 over witch would make your stock b18c1 81.5mm, so you first buy the pistons then give them to the machine shop and he will measure the pistons and bore the block to the spec sheet(that comes with the pistons)

 

Yea, what he said ^^^^

I am putting 81.25 JDM ITR pistons in my gsr block and I plan to do the same thing.