Embodiments provide combined valve actuating device with specialized actuating cams for hydraulic lash self-adjustment, including an actuator fixedly mounted on a rocker arm shaft and a rocker arm mounted with a hydraulic lash adjuster. The actuator is provided with a primary piston and an actuating piston. An actuating oil line is disposed between the primary piston hole and the actuating piston hole. The actuating oil line is connected to an oil supply line through a positioning and pressure control unit. A hydraulic linkage is formed between the primary piston and the secondary piston and an actuating valve is opened when oil is supplied to the actuating oil line.