PURPOSE: To improve the scuffing resistance and pitting resistance of a cam/ rocker arm pair which consists of a cast alloy iron and is subjected to a suitable film treatment by finishing the contact surface of said pair by polishing then providing a plane thereto at an adequate area rate.

CONSTITUTION: The contact surface of the rocker arm with the cam of the cam/rocker arm pair constituted by combining the cam which consists of the cast alloy iron and of which the surface is subjected to a manganese phosphate film treatment and the rocker arm consisting of high chromium cast iron is finished by polishing and is further subjected to barrel polishing by which the plane of ≥30% area rate with respect to the polished surface is provided to said surface. The lubricity of the contact surface by a lubricating oil is thus improved and the cam/rocker arm pair having excellent scuffing resistance and pitting resistance is thus obtd.