1. AN ENGINE COMPRISING A CYLINDER, A PISTON RECIPROCABLE THEREIN, A CRANK-SHAFT OPERATIVELY CONNECTED OF SAID PISTON, A CAM-SHAFT DRIVINGLY CONNECTED TO SAID CRANKSHAFT, A FUEL INJECTION DEVICE, A WATER INJECTION DEVICE, AND FIRST AND SECOND CAMS ON SAID CAM-SHAFT FOR ACTURATING SAID RESPECTIVE FUEL AND WATER INJECTION DEVICES IN TIMESPACED RELATION, SAID SECOND CAMBEING AXIALLY SHIFTABLE ON SAID CAM-SHAFT BETWEEN FIRST AND SECOND POSITIONS, THERMOSTATIACALLY CONTROLLED MEANS RESPONSIVE TO ENGINE TEMPERATURE FOR AXIALLY SHIFTING SAID SECOND CAM FROM SAID FIRST POSITION TO SAID SECOND POSITION WHEN THE ENGINE TEMPERTURE RISES TO A PREDETERMINED VALUE AND FOR AXIALLY SHIFTING SAID SECOND CAM BACK TO SAID FIRST POSITION WHEN THE ENGINE TEMPERATURE DROPS FROM SAID PREDETERMINED VALUE, SAID SECOND CAM WHEN IN SAID FIRST POSITION BEING IN ACTUATING RELATION TO SAID FUEL INJECTION DEVICE CONJOINTLY WITH SAID FIRST CAM AND BEING OUT OF ACTUATING RELATION TO SAID WATER INJECTION DEVICE, AND SAID SECOND CAM WHEN IN SAID SECOND POSITION BEING IN ACTUATING RELATION TO SAID WATER INJECTION DEVICE AND BEING OUT OF ACTUATING RELATION TO SAID FUEL INJECTION DEVICE.