An internal combustion engine has a pair of opposed pistons held within an elliptical guide of the engine housing. The pistons reciprocate within a cylinder attached to a shaft. A combustion chamber is formed within the shaft and positioned to be between the pistons. Combustion of fuel causes the pistons to reciprocate and reciprocation of the piston causes rotation of the shaft. A valve having an intake and out take port provide fuel and exhaust to the combustion chamber. A bridge extending upwardly form the bottom of the combustion chamber prevents fuel intake from exiting the exhaust before combustion.