A central actuator for a magnet valve of a cam phaser, the central actuator including a housing that envelops the central actuator; a pole tube and a pole core that are arranged within at least one coil that generates a magnetic field; an actuation plunger that is arranged at an armature that is axially movable in a direction in an armature cavity; a closure element that closes the armature cavity, wherein the closure element includes at least one pole core insert that includes a central bore hole and a support bushing that is arranged in the central bore hole of the pole core insert, wherein the actuation plunger is supported axially movable in the support bushing, and wherein the closure element includes a closure cover and is provided as a pre-assembled module.