In a motor vehicle having a motor block secured to the chassis in a front portion of the vehicle, means projecting along the direction of travelling associated with the motor block and arranged above the center of gravity of the motor block, the arrangement of the projecting means and the securing members being such that during an impact having a certain force magnitude effecting the projecting means causes the motor block to rotate with its end facing the passenger cabin of the vehicle downwardly towards the road by creating a rotational momentum pivoting the block downwardly.