https://www.coximport.com/jepistons/apps.html

This page gives a list of sizes for certain applications so im going off that right now.

I have a B18c1 with 81mm JE pistons. Im trying to replace the rings because mine got fucked up.

So, i just measured my bore and its 3.210 and i also measured my pistons and they are 81mm 9.8:1 compression.

Looking at the application chart, it says that for a bore of 3.209 it should be 81.5mm pistons.

Orginally i had ordred the rings for 81mm pistons w/ 9.8:1 compression but the gap was huge. like .063 on the new rings compaired to .018 on the old rings.

Something dosent seem to be adding up here...

Engine has 15,000 miles on it with those pistons/rings. But i didnt put it it together.

Could they have just used file fit rings?

after doing the math.....

bore 3.210
piston 3.188 <81mm>

which is a .022 diffrence so that would leave a piston to wall gap of .011 on each side?? dosent that seem kinda big? i thought it was supposed to be around .0028?
But like i said, it did run about 15,000 miles before the rings got washed <fuel> and started to leak <oil coming out the exhaust><reason for replacing the rings>

 

anyone????

 

sounds like you have some major issues going on with that...IF all the measurements you posted are absolutely correct.

i'd double check to make sure you are accurate. Sounds like someone has been in that motor before. It might be .040 over, but i couldn't tell you for sure. Eitherway your pistions and rings sound incorrect.

 

Its possible that it was built with a 81mm piston with a 81.5mm bore and 81.5mm rings.Typically JE's are measured 1/2" up from the end of the skirt.If you measuring it at the top it will be considerably smaller.
Glenn

 

the JE pistons is stamped on 81mm, i was told if they were 81.5 mm that the stamp would say that.

its begining to look like 81.5mm rings were used. What if any are the pro's and con's for using such a larger ring and having that bigger piston to wall clearance?

 

I can't believe it didn't sound like a cement mixer with that much clearance.Typically the skirts will break with that much clearance.You won't get proper ring seal with that much piston clearance.As the piston rocks it will pull the rings away from the cylinder wall.You really should replace the pistons now as well as the rings if the really are 81mm.
Glenn