Abstract: An arrangement for an electromagnetically operated actuator for a displacement-type engine having a spring-mass valve actuating oscillatory system which includes a valve having an armature thereon and a pair of electromagnets for maintaining the valve in at least first and second final operational positions of the maximum amplitude of vibration, the armature and at least one of the electromagnets comprising a contact dampener for the armature, at least one of the electromagnets being mounted in the housing by a hydraulic length-compensating element such that the distance between the valve seat and the pole area of the electromagnet is adjusted to correspond to the distance between the valve head and the pole area of the armature, so that the desired amount of dampening is consistently effected as the armature approaches the electromagnet and the valve approaches its seat.