read thru these links also
viewtopic.php?f=53&t=247&hilit=gaps
viewtopic.php?f=53&t=509
viewtopic.php?f=53&t=1795
viewtopic.php?f=50&t=1268
since I can,t closely examine the components I can only go on what appears to be in the picture,you'll need to carefully measure the bore and piston diam, and ring end gap, and have the piston and ring manufacturers look at the piston, and verify the oil level, pressure and the hone job were done correctly
this picture suggests the best clues, obviously there's been piston skirt to bore wall contact to produce those wear marks on the piston skirt , oil film in the clearance between them should prevent that, I can,t be 100% sure without a close physical exam but it APPEARS from THAT picture that the rings ends might have butt, or touched or locked up as they expanded and rode against each other under some conditions,(not the right end gap) that would cause them to expand firmly into the bore wall, or the bore to piston wall clearance was a bit too tight, or the amount of oil on the cylinder walls was not ideal, possibly,but it sure looks like the end gap on the rings was not large enough, or the engine heat too high , too early in the break-in process, due too low of oil flow, or clearance issues, look closely at both the ring ends which in the picture seem to have indicators of riding against each other AND the un- even ring edge wear, indicating the ring rode in a slightly distorted condition firmly against the bore , notice how the wear is more pronounced near the end gaps and tappers to less worn as the distance from the end gap increases?
there's also what appears to be indicators of less than ideal piston skirt to bore clearance, where there was less oil trapped on the bore wall to piston skirt to keep them floating on a film of oil that the rings should be pushing back down on the power stroke, oil that's supplied with splash oil misted on the cylinder wall, and ideally forms a supportive film to keep the piston skirt from direct contact with the cylinder wall.
The most common break in related, piston to bore seizure, or partial seizure is usually caused by the ring not the piston. Most new piston rings come with coating on their outer sealing surfaces. This coating seals to the cylinder wall in just a few operating minutes, which provides better power during the break in period. As the engine is breaking in, the coating eventually wears away and lets the hard surface of the ring advance outward to the bore surface from behind to provide the long term seal. the hone job on the bore provides micro grooves that hold oil on the cylinder walls and naturally you need to follow the manufacturer of the pistons bore to cylinder wall clearance recommendations, and hone recommendations and a deck, torque plate needs to be used during the bore/hone process, The down side of this coating on the ring mating surface is that it increases the ring diam, slightly for a dangerously small end gap during the first minutes of operation, until the rings seat, properly and the coating has worn away,. If the engine is run too hard too soon,or there's not enough oil clearance between the piston and bore the heat will cause the ring to expand in diameter which will drive the ring ends together,if the ring gap was minimal, (if there was not a minimum of about .004 thousandths of ring end gap per inch of bore diam. and in some cases MORE IS NEEDED)) and drive the ring surface hard against the cylinder wall. A piston ring that is being overheated in almost any fashion, due to lack of oil flow excessive heat or non-correct clearances will easily have enough tension against the cylinder wall to scratch off the oil film which will begin the scoring/seizure process. A piston seized in this way will have heavy scoring around the entire diameter of the piston, with the ring usually locked into the groove all the way around as well.
the other possibility is that the wrong rings and ring clearances were used on that piston, if the rings did not have the correct back spacing and side clearance on that set of piston grooves they were matched too and installed in,,it would result in similar wear
http://forum.grumpysperformance.com/viewtopic.php?f=51&t=588&hilit=+plates
http://forum.grumpysperformance.com/viewtopic.php?f=53&t=509&p=632#p632
http://forum.grumpysperformance.com/viewtopic.php?f=53&t=110
read thru this LINK
http://www.babcox.com/editorial/ar/ar80125.htp
"Piston Scuffing
This is a sure sign of overheating and/or insufficient clearance. When an engine runs hot, the pistons swell up reducing the clearance between the piston and cylinder. The cylinder bore can also distort from localized hot spots, further adding to the problem. If a piston gets hot enough, it will scuff the wall wiping material off the sides of the piston. Where this occurs will give you a clue as to the cause.
If overheating is involved, the scuffing will be primarily on the upper ring lands and on the sides near the wrist pins. There may also be oil carbon and lacquer burned onto the underside of the piston indicating it was unusually hot.
The presence of scuff marks on the lower skirt area would tend to indicate a lubrication problem rather than an overheating problem. Scuff marks on the edges or corners of the thrust sides of the piston would indicate bore distortion as the culprit. Scuffing on both thrust sides would indicate binding in the wrist pin.
Any time you find evidence of scuffing, therefore, it’s important to diagnose and correct the underlying cause to prevent a repeat failure.
If the engine was recently rebuilt, the scuffing problem may be due to insufficient assembly clearances. The only way to know is to measure the pistons and cylinders. Measure the pistons at the top, center and bottom of the skirt area in two directions (parallel to the wrist pin and perpendicular to the wrist pin) to see if the pistons are within the manufacturer’s specifications.
If the pistons are the correct size, then measure the cylinder bore at the top, middle and bottom, also in two directions (parallel to the crankshaft and perpendicular to the crankshaft). This will tell you how much taper is in the bores, and if bore distortion is a problem. By subtracting the piston dimensions from the bore dimensions, you can figure the piston-to-cylinder clearance. If the clearance is within specifications, the underlying problem is overheating.
Many aftermarket replacement pistons today are available with moly coated skirts to protect new pistons against scuffing. The coating also allows you to run slightly tighter clearances to reduce piston noise when the engine is cold, and blow-by. Upgrading to coated pistons is probably a good idea for any engine that has a history of scuffing or may be prone to detonation or overheating. Think of it as insurance against piston problems."
http://forum.grumpysperformance.com/viewtopic.php?f=51&t=588&hilit=+plates
your comments on the ideas presented?
