When installing a shorter connecting rod than a crankshaft was meant for, it is sometimes necessary to clearance the counterweights. A quick reference we do is to use the shorter connecting rod as a guide to mark how much counterweight needs to be removed. First, with your piston installed on the rod, mark the point on the counterweight that first contacts the bottom of the piston as you rotate it around the rod journal. Next, with the piston removed, place your sharpie at the point that was clearing, and hold your sharpie in that position on the rod. Now as you rotate the rod the rest of the way around the rod journal, it will mark the counterweight showing you how much you need to remove to have that same amount of clearance the rest of the way around.
Don Ott Racing Engines
York Springs, PA