Engine with known mileage?
I don't like the look of all that piston top flaked carbon that can fly around. Carbon is a bad sign. Seems like hotter plugs, or oil-burning plugs might help reducing future carbon build up, but that's just temporary, or better said; not the best solution for engine longevity. Irregular piston wall glazing is questionable too. Me, I'd tear down the engine, and plasti-gauge the rod bearings, then after using a ridge-reamer tool, push up the rods/pistons up out of the cylinder holes. I'd buff the cyl. walls as directed in any book to get the proper diagonal-angled buff pattern, (60 degrees?). Be prepared to at least obtain new rings, and rod bearings. You might be able to get away with the same sized rings, and bearings.., but that is best left for future discussion with others with better memories, hands-on experiences to share with you, i.e; the use of proper dial/caliper gauges, feeler gauges, readings, etc., in order to comprehend if you have standard, oversized, OEM installed parts. I have gone to NAPA, and managed to; just once, get just one standard piston, rod, piston pin, and rings as a single replacement set. What a hassle. Seems most stuff comes in complete sets.., so me.., I'd go with the latter, and do the whole job.
Old school methods of installing new rings is ok with me, i.e., ridge-reaming the tops of the cylinders, removing piston(s)/rod(s). With good lighting, sunlight, or spot light, magnifying lense; pulling all rings out/off of a piston, and then carefully cleaning out each groove with a ring that has been broken in two using the factory squared ends in order to push, pull, but mostly push out any stuff within the groove via this type of home-made tool. There are professional tools for that too, which are faster, and better at preventing any overdone digging/nicking. Anyway you do not want to scrape any aluminum away from the sides, or bottom of the ring grooves, just carbon, and gunk stuff. Once done, (with freshened piston grooves), new appropriate sized rings can be installed, (given that the pistons are tight from axis slop, i.e., none from end to end), and reinstall after the buffing job to the walls. Your walls don't seem too bad as I don't really see any scratches, just wear, and glaze. The wear looks to me to allow oil to travel vertically along those wear zones, and perhaps to allow extra oil to be where it is not wanted, and then mixed in with the air/fire/fuel mix creating the carbon deposits. So far we are just talking about one cylinder, but while there I'd do all of them.
However.., In a pinch, just do that one.., If you do not want to do a complete tear down, that is..! If you do just that one piston, without the plasti-gauge business, then you would just undo the rod cap to the crank, pull out that one piston, and rod-part, (remember; after ridge reaming), and then just buff up that one piston wall. Prior to buffing be sure to cover the crank with towels in such a way as to be able to remove them after buffing in order prevent any crap that will fall down onto any metal surface below the hole. In a pinch you could use the same rings as long as they are positioned correctly, and the same rod bearings.., in that pinch. BUT I would not do that. I would at least install new rings, in cleaned piston grooves, in order to interface with the buff job.., and after only ascertaining that the rod bearings were within spec. ...in a pinch.., just saying.
As a side-note; Back in the carb days.., I knew a fellow that got a brand new vehicle where the engine cylinder walls were mirror smooth, (talk about OEM quality control), and he had extremely low psi in each cylinder. He took a scouring powder, Bon Ami, and introduced a tablespoon of it down the carb, slowly sprinkling, taking the revs up, and down. Then he'd check the psi's until proper. It was good to go for the normal life of that type of engine. Must have taken him a day's worth of messing around though, lol. Bottom line, it worked. Me, I'd opt for the proper mechanical method of de-glazing that wall of yours, i.e., with a drill, and proper attachment, i.e., a professional one. Yours seem to be mirror glazed. Some like that, I don't.., when it comes to getting rings to marry to the walls.
I can see reasons to have a mirror cylinder wall finish with the use of chromed rings, (old school short-lived racing engines), but for our vehicles a more standard approach is best. Take any engine repair book, and they are showing us a rather universal method at cleaning up our cylinders to be ready for replacement rings in order to get a better balanced psi within each cylinder when completed. Balance is key.
Break-in procedures are a must, i.e., proper highway up/down rpm levels, changing out the oil after such miles as indicated. WHAT? 500-750 miles or so, I think, and then doing an in-service-check by loosening those new head-bolts you used, (right?), and re-tightening them down to spec.
Anyway, that's my two cents at the moment, but there are real mechanics on
that can, and will give you, hopefully, better guidance...
