1. Remove the crankshaft and pistons. Check the piston for distortion or cracks. Measure the piston diameter at a point 11 mm (0.4 in.) from the bottom of the skirt. There are two standard-size pistons (No Letter or A, and B). The letter is stamped on the top of the piston. Letters are also stamped on the block as cylinder bore sizes. Piston Diameter
   Standard (New):
   K20Z2 Engine:
   No Letter (or A): | 85.980−85.990 mm (3.3850−3.3854 in.)
   B: | 85.970−85.980 mm (3.3846−3.3850 in.)
   No Letter (or A): | 86.980−86.990 mm (3.4244−3.4248 in.)
   B: | 86.970−86.980 mm (3.4240−3.4244 in.)
   No Letter (or A): | 85.930 mm (3.3831 in.)
   B: | 85.920 mm (3.3827 in.)
   No Letter (or A): | 86.930 mm (3.4224 in.)
   B: | 86.920 mm (3.4220 in.)
   Oversize Piston Diameter
   K20Z2 Engine:
   0.25: | 86.230−86.240 mm (3.3949−3.3953 in.)
   0.25: | 87.230−87.240 mm (3.4342−3.4346 in.)