The cylinder head is the metal part of the engine that encloses and covers the cylinders. Bolted on to the top of the block, the cylinder head contains combustion chambers, water jackets and valves (in overhead-valve engines). The head gasket seals the passages within the head-block connection, and seals the cylinders as well. Henry Ford sold his first production car, a 2-cylinder Model A, on July 23, 1903.