Abstract: A hydraulic control system for controllably directing pressurized engine oil to deactivation valve lifters to activate or deactivate the associated engine intake and exhaust valves. Passages to the lifters are controllably opened or closed by a solenoid control valve responsive to signals from a computerized engine control system. Preferably, the hydraulic control system includes a top plate having a first pattern of channels and bores formed in its underside, and a bottom plate having a second such pattern formed in its upper surface. The top and bottom plates are joined to form a hydraulic distribution manifold mounted on the engine. In a presently preferred embodiment, a gasket plate having bores and patterns of resilient gasketing material is provided between the top and bottom plates to simplify fabrication of the top and bottom plates.