Abstract: A method and apparatus for increasing the power of internal combustion engines is disclosed and includes the method step of injecting pure oxygen, under pressure, into the combustion chamber of the engine after ignition of the usual fuel mixture. The apparatus includes a source of oxygen under pressure, suitable lines leading to a distributing valve which is controlled by the cam shaft of the engine and suitable lines leading from the distributing valve to the individual cylinders. The apparatus also includes a one way check valve to avoid back feed of exhaust gas into the oxygen system.