Hydraulic actioning device for an internal combustion negine

The actuator has a unit including two passages and a control unit to control fluid flow between lower and upper chambers (24, 25) by valves. The unit maintains a piston (22) at a fixed position or adjusts position of the piston in a body by selected passage of fluid between the chambers due to pressure difference in the chambers, when a force is exerted on the piston by a hinged type connecting rod assembly. An independent claim is also included for an internal combustion engine.