The top end of the connecting rod are mostly thin-walled circular structure for reducing wear between the piston pin and the thin bronze bushing into the hole in the head. In the drilling head and bushing or slot milling, with the surface to make a splash of oil foam into the lubrication bushing and the piston pin.
The body of the connecting rod is a long rod in the work force is larger, in order to prevent the deformation of the rod body must have enough stiffness. Therefore, the engine's connecting rod is mostly used in section I, Section 1 in stiffness and strength are sufficient condition minimum quality, high strength engine using H shape section. Some jet engine uses oil cooling piston connecting rod, to be in the shaft longitudinal drilled hole. To avoid stress concentration, the connecting rod body and head, the bulk of the connecting parts are used in circular smooth transition.