A valve assembly for an internal combustion engine includes: at least two valves supported by a pair of valve stem holders; a bracket; a closing actuator for pivoting and closing the valves upon contact with a closing lobe of a camshaft; one or more opening actuators for opening at least one of said valves upon contact with an opening lobe of the camshaft; and one or more Belleville spring washers, allowing for an adjustment of a sealing load when the respective valves are closed.