A more precise home shop way to determine appromately the cylinder wear is with the use of a piston ring.
We need a ring from the engine that is the least worn and that is usually not the top ring.
Clean fairly well the ring and the cylinder.
If a ring had .000 end gap when inserted in the cylinder and squared up-and we caused the ring or the cylinder to lose .001 from the cyl ID or the ring OD the gap would increase by .0031416 in.So if we use the piston without rings to push the ring we selected down the cyl into the unworn area below normal ring travel, and measure the gap, then bring the ring up to the most worn area at the top and measure the gap, the difference in the two measurements divided by 3.1416 will be the increase in bore.Roughly speaking , a increase in bore of 1 thousanths/inch will result in a growth of ring gap of 3 thousanths/inch.
If the measurement in the unworn area was .165 and the measurement in the wear area was .190,the difference is .025 divided by 3.1416 and the wear would be .0079 or nearly eight thousandths.
Of course the wear is never equally distributed so the worn area is not round but this is an average measurement of wear in the measured area.
Last edited by enginenut; 01/08/2011 3:12 AM. Reason: mistake
