An engine includes a housing defining an annular bore and a piston assembly disposed within the annular bore. The engine includes at least one valve configured to oscillate between a first position within the annular bore to allow the piston assembly to travel from a first location proximate to the at least one valve to a second location distal to the at least one valve and a second position to define a combustion chamber relative to the piston assembly at the second location. The engine includes an exhaust gas port disposed in fluid communication with the combustion chamber and a fuel distribution assembly configured to mix fuel from a fuel source and air from an air source into a fuel and air mixture at a location external to the combustion chamber and to deliver the fuel and air mixture to the combustion chamber.