Abstract: A single cylinder head design used for a series of engines using different cylinder bore diameters with a small diversity of parts. The cylinder head mounting holes and the valve stem guide openings for the breathing valves 4, 4a are the same for the series of engines. The cylinder head 2 is designed for the internal combustion engine of the series having the largest cylinder, wherein the valve disks 6 extend into the cylinder peripheral region of the part of the cylinder head 2 cooperating with the cylinder in forming the combustion chamber. When the cylinder head 2 is used for a small bore diameter engine of the series, the cylinder head is equipped with valve seat inserts 7a having a small diameter valve seating face and the valves have a corresponding smaller diameter complimentary seating face.