Abstract:The selection of valve cam base circle radius influences the structure size, contact stress and lubrication of cam mechanism. The contact stress of valve cam was analyzed based on the Hertz formula, the elastohydrodynamic lubrication was analyzed based on elastohydrodynamic lubrication theory, and the relationship of cam base circle radius, contact stress and lubrication coefficient was got. The results show that the increase of base circle radius of cam can reduce the contact stress, but it may not improve the lubrication of cam. In order to meet the special requirements of contact stress and lubrication for the valve cam with a given movement, and ensure the reliability and durability of valve cam, the selection of cam base circle radius should be constrained by the Hertz formula and elastohydrodynamic lubrication theory.