Presented is a very low speed, high torque, horizontally opposed, rotary, valveless, Otto cycle piston engine producing four power strokes per revolution, the engine consisting of a fixed engine case assembly having upper and lower plates, the engine rotor assembly having upper and lower plates, sandwiching a single, closed ended cylinder assembly, the cylinder containing intake and exhaust-intake ports, independently reciprocating power and head pistons, each piston being reciprocally controlled by its vertically projecting piston bearing sets contacting respective sets of upper and lower, inner and outer peripheral cam plates, the engine being thus rotated, the cylinder being lubricated by a sealed, recirculating air-oil mist system, the engine rotor assembly having a lower, vertically projecting gear box housing containing a gas porting cap, a vertical drive shaft, two counter rotating output shafts, intake and exhaust pipes, and an exhaust gas filter canister.