Abstract: A 4-cycle, 4-cylinder internal combustion engine which comprises a hollow cylindrical engine casing with only three moving parts, a single rotary piston wall and two rotatable valve cylinders. A hollow cylindrical motor casing is divided in half vertically by an internal dividing wall. A single oil-cooled rotary piston wall is pivotally attached to the center of the internal dividing wall to create four variable size cylinders as the rotary piston wall pivots back and forth with the firing of the four spark plugs each firing into one of the four cylinders.