Abstract: An internal combustion engine including a camshaft journalled in a bearing for rotational movement therein. The camshaft includes a main oil passageway extending axially therethrough and is in flow communication with the oil sump. The camshaft further includes an auxiliary passageway extending from the main passageway to a sidewall outer surface of the camshaft. A first lubricating passageway is formed within the crankcase and extends from the camshaft bearing to the cylinder head, and a second lubricating passageway is formed within the cylinder head and extends from the first passageway to the upper portion of the valve rocker mechanism of the engine. As the camshaft rotates upon engine operation, the auxiliary passageway in the camshaft is in periodic flow communication with the first passageway to provide a pulsed flow of oil to the first passageway. The oil then flows through the second passageway and lubricates the valve rocker mechanism.