An engine includes a hydraulic pressure lash adjuster (HLA) pivotally supporting an end of a swing arm and having a valve supporting the other end of the swing arm, wherein the hydraulic pressure lash adjuster includes a housing, a plunger of which one end portion thereof may be slidably inserted into the inside of the housing, the other end portion of which extends outwards and supports the end of the swing arm by selectively moving upwards or downwards in a length direction of the housing, a stopper pin slidably mounted in a chamber of the plunger so as to selectively lock the plunger to the housing such that the plunger cannot move in the housing, and a hydraulic pressure supply portion that selectively supplies one side of the stopper pin with a hydraulic pressure in the chamber of the plunger to move the stopper pin toward the housing.