im rebuilding the motor in my 91 indy 400.nothin wrong with it just want to do it again after 7000 miles.i noticed that the pistons in this sucker only has 1 ring.my dealer says thats all he can got for it .now i noticed that there was signs of blowby on one of the pistons it was all black down one side]my dealer said it was because the rings were worn.my problemis i dont want to put back pistons with just one ring on them and what i wanna know are there any pistonsthat have 2 rings for this motor.my dealer says no something to do with borestroke.if there arent any for the 400 i was considering punching it out to 440 cc and putting in a set of wiseco 440 2 ring pistons any help in this matteris appreciated

Why do you want 2 rings? If the originals lasted 7000 miles and you said it ran good then if you freshen it up with new pistons and rings should be good to go. Believe they went to one ring pistons to lower the drag in the cylinder.

There is nothing wrong with a 1 ring design, In fact, it's probably an L shaped ring? These offer better combustion rebound and lower upstoke friction, very effective design and used in some high output engines. I recall the mach's of that era having the same design.

Anyways, if your questioning what needs rebuilding, you need to do a few checks.

Check your rod side deflection and play, measure the cylinder bores and check your ring end gap. These are key indicators of what needs rebuilding.

Good luck