The connecting rods are sorted through and checked for balance in two ways. First, all rods in the engine should be of identical weight. To accomplish this, the machinist takes the lightest rod and the rest are reduced in weight to match. The rods are also checked for weight distribution between the big and small ends. Here the small end of a rod is being weighed. All rods should have equivalent mass percentages at both ends from one rod to the next for all eight rods. Verify this stuff now and you'll get a smooth running engine that will stay together.