Mine also seemed to have a bit of piston movement side to side. It has about 85,000 miles on it. I think it's more important that the cylinder wall does not have a ridge at the top from piston ring wear. Mine was almost imperceptible so l left everything alone. I still haven't ran the engine yet but i'm not going to loose sleep over it. New valve seals and a repaired valve cover and pcv system will prevent 90% of the oil usage from these things.

 

Here's a screenshot of the info you're asking about. There's also another chart with ring data. Sounds like you haven't yet been made aware of this site --- it's highly recommended when you're getting into the DIY phase of repairs.

 

There is some good info thanks OBW. If a round feeler gauge is put between the cylinder and piston then the max you should be able to get in there would be .130mm?

 

That's the way I read it --- for assembled engines. Since the cylinder probably isn't round any more, I'd check it several places around the circumference. If you measure with the piston at TDC, make sure the ridge has been removed before measuring.

I'd guess that the "Piston Running Clearance" is for measuring piston dia. vs. cylinder dia. on new bores and pistons. I don't claim to be an experienced engine builder.

 

With that information I'd measure on the thrust side of the cylinder wall in several locations of piston travel. Then you wouldn't have to muck with the ridge if not needed. My pistons had some play but the ridge was almost unfeelable (ha a new word).
the old chevys I've worked on there was more of a concern with ridge then piston wear. I dont know if these pistons or rings are softer than the old chevys. I would think these would have low tension rings. Only an uneducated guess though