 Andy: In my opinion, that is not the right way to measure the piston clearance, and you'll probably point yourself toward too much overboring if you do. Since you are at the last overbore (.125") before sleeving back, I would be really careful about going too large. You need to measure that piston top to bottom, in three sections, left to right and fore and aft, so you get the dimensions of the "cylinder" that the piston fills. Many times pistons are no longer the correct form. Remember, because of some piston design, pistons are not always round. Many have an eccentric form established by a master cam on a rotary mill. Get the correct measurements from a book, then compare those to your piston. If the piston is squished in one direction and fat in another, you can re-form them with a deadblow, soft-faced hammer. The JD official service book even shows that procedure for tractors like my 70D, when Deere began to install aluminum pistons from the factory. Check your pistons carefully, 6 places, using a proper micrometer, not with a feeler gauge. Also, have you checked the ring end gap by sliding each ring squarely using the top of a piston, and measuring the remaining gap? If the ring gap is good, and then you over bore to "fit" the piston, you'll have an excess ring gap, and risk some permanent blow-by. Before I would give up any of that bore which you can never get pack, I would get a good, known, quality, 5-6" mike, not a caliper, and measure until I was certain that I knew the true shape and form of those pistons. Frank
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