This is an old post, but there are a lot of assumptions being made here. Since the measurement is taken just below the oil ring on the old style piston, it makes Kohlers piston clearance seem large at .007+. When you measure an old style Kohler piston just below the oil ring, that area is not the largest diameter of the piston. The largest diameter of the piston is at the bottom of the piston. The pistons are cam ground (oval), and tapered from top to bottom. If you have .007 clearance just below the oil ring, you will have .002-.003 clearance at the bottom of the skirt. This is where the machine shop screw ups happen if the machinist sets Kohlers recommended clearance at the bottom of the skirt instead of just below the oil ring. If the piston clearance is .007-.010 at the bottom of the skirt, new ring gaps will be large and there will be piston slap. I've read about people running into this problem. Why Kohler decided to instruct people to set the clearance just below the oil ring is beyond me. It's made for a bit of confusion and overbored blocks over the years. I measured the piston clearance on an NOS K301 and an NOS K321 mini block. At the bottom of the piston skirt, the clearance on the K301 was .003 and on the K321 a tight .002. The compression and oil ring gaps were .012-.015 which is what I would expect.
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