"5/16" X 12- I found ever
"5/16" X 12- I found everything quite clean- however I did find the following:
Bottom 2 pistons with low compression had ring lip on cylinder wall more pronounced than top of same cylinder and other pistons did not have this.
The rings removed from same low compression cylinders were thinner (.020"/ 0116 vs .136)) measured ID to OD, opposite side from gap. I checked one of the higher compression pistons as a baseline and found .002-004 varition. Something is out of round-or wearing hard towards bottom of engine.
Pistons from both higher compression and low compression cylinders all have have lower skirt scuffing- no cylinder wall damage visable and no transfer of aluminum."