connecting rod bottom ends can stretch and distort at high loads and rpm's. If there is too much crankshaft end play the surface can be rounded instead of flat in that direction. the rebuild process is to machine the flat connecting surface, then bolt the pieces together and torque. that then makes the hole a modified oval, then machine the hole round to the correct size. the piston end on some rods have a bushing that can be replaced then machined to size, , also the rod can be twisted, and requires straightening, this machine work can shorten the center to center length which cannot be corrected. removing material can effect balance so that is the next step in a performance engine.