Abstract: A control system that allows continuous adjustment of a position of an actuator jack used to change compression rate of a heat engine, with mechanical-type regulation. A source of pressurised fluid is linked to a circuit to allow movement of the jack in two opposing directions. A servo-control device connected to the jack includes a mechanism to distribute fluid to control the position of a mobile element of the jack. A lever articulated with the mobile element of the jack in an initial articulation point includes a second articulation point with a mobile control unit in transfer controlling the distribution mechanism. The lever is able to turn around the initial articulation point via action of a control moving the driver assembly of the lever, connected to a third articulation point at the opposite end.