Abstract: In a four stroke cycle reciprocating internal combustion engine, four dual functionable combustion chambers and two power trains to crankshaft are comprised of a single stationary cylinder encasing two quadruple faced rotor-reciprocative pistons, further encasing a rotatable intake-exhaust manifold geared to an external rotatable crankshaft. The crankshaft is connected by connecting rods to driving arms on external extensions of the two pistons.Two such units connect to a common crankshaft to comprise an eight combustion chamber engine.Upon each crankshaft half turn stroke the two pistons of a unit and associated intra-engine power trains to the crankshaft move simultaneously in opposed directions to expand two chambers for intake and combustion and to contract the other two for compression and exhaust functions.