The small end of the rod is sent out to the machine shop to get milled down. We take a bit extra off for clearance between the piston and rod.
The rods and crank we received were from preproduction units. The big end of the rod journal was on the tight side, while the crank OD was on the big side. When we went to measure out for the bearings, we found that the clearance was to the point that there was no bearing to select from. This was an easy fix, however, since we were at the end of the spectrum where the rod ID could be opened up to a bearing spec of our choice. We also found that the small end of the rod was too thick for our box-style piston. Since the wrist pin was shrunken down, the actual thickness of the rod wouldn't fit. The thickness of the rod measured out to 24.79mm while the gap from pin journal to pin journal was 20.3mm. Since our piston is already so narrow, we decided that it would be wiser to have Ultra Performance Machine mill down the small end than cut out anymore material from the piston. We had them cut the rod down to 19.3mm giving us a 0.5mm clearance on each side of the rod.