Here's an unusual question from an admitted novice. I have a set of .040 over KB pistons and a new set of KB 4000BM8.060 rings for a .060 over bore. Old school engine builder friend of mine says rings can be filed to fit and will work fine. Any input appreciated.

Thanks MoParts

up to .010" over would be OK but that much will make an ovaled ring in the bore as it's about more than just reducing the circumference until it fits. When done the .060" rings would not be concentric in the bore.

IMO with KB pistons it will take a lot of filing and like Robert said it may not be perfectly round when finished due to the amount required to take off to get the proper ring gap on a KB piston. KB pistons take a much larger gap due to piston composition so even standard .040 rings have to specially filed for the specified gap or you will have piston problems. In a pinch with standard manufacture pistons it may work but with the KB's I would not even think of trying it.

Thanks People.

I didn't really like the idea but I don't know what I don't know. New ring set certainly isn't going to be a deal breaker.

Maybe you can get a dealer to trade ring sets with you.

Not only not concentric ... but how about the additional pressures placed on the cyl walls ?

Guy's, the radius of the .060 over rings are bigger than the radius of .04 over rings. Filing the ring end gap will not change the radius of the rings! Just my opinion!