Abstract: This invention provides a valving arrangement for a reciprocating engine in which there are two valve assemblies, each with a pressure responsive valve member. As the piston approaches the end of its stroke in either direction, the exhaust port is closed, such as by an extension on the piston, causing fluid pressure to build up in the end of the cylinder. This pressure is conducted to the valve assemblies through fluid lines, causing the pressure-responsive valve members to move in response to the pressure build-up in the end of the cylinder. These valve members control the inlet and exhaust connections to the cylinder so that the piston is caused to reciprocate by the working fluid as the valve members are moved pneumatically to open and close the lines.