The invention relates to a measuring unit dowel device with a parallel guide mechanism, which comprises a fixed and movable guide parallel parallelogram pillar with a fastening part and at least two fastening components mutually connected through a guiding element. Every fastening component has at least one hole vertical to the corresponding parallelogram pillar relevant surface and at least one hole fastens a bearing element to the dowel device and or fastens the dowel device to the engine body or the middle support element. The parallelogram pillar has a slot-shaped notch. The fastening component is provided with an elevated fastening mat area corresponding to the parallelogram pillar. The fastening part is separated from other parts of the parallelogram pillar through a first slot-shaped notch which passes through the parallelogram pillar. When the projection is at the plane extending through the fastening component vertical to the parallelogram plane at the moving direction of movable guide parallelogram pillar, the cutting shape area of the slot-shaped notch at the parallelogram pillar is corresponding to the surface of the parallelogram pillar, extending within the opposite side of the fastening component.