Do you have iron pistons? I have never worked on that style engine so like I said it might be something I have never seen before. You are at about the right time in Chevy's history to have either kind. I don't know just when and for what models the change occurred. But I would bet that the rings would be different for cast iron pistons and aluminum pistons. Some one on here will know and that is what is so great about this site. Iron pistons might very well have had rings like you describe. Oil control would be very different with each type of piston.
