PURPOSE: To provide an integral air compression mechanism of an internal combustion engine for reducing costs and weight of an engine, and for generating compressed air from a part integrated with the engine in order to improve performance and reliability.

CONSTITUTION: This system includes a valve means 32 associated with one 20 of a plurality of combustion chambers 20, 21. A housing 42 is connected to a cylinder head 18 and has first and second bores 44, 46. A master piston 50 is disposed within the first bore 44 to define a first oil chamber 52. A slave piston 54 is disposed within the second bore 46 to define a second oil chamber 56. The master piston 50 is forced toward the first oil chamber 52 when another one of the combustion chambers is in the exhaust stroke. The second oil chamber 56 becomes pressurized and the valve means 32 is opened to the slave piston 54 during the compression stroke of the one combustion chamber 20.