The following pictures shows Volkswagen Beetle Engine Diagram, which applicable for 1200, 1300, 1500 and 1600cc engines from 1954 to 1974 model series. These four cylinder engines are of an air-cooled horizontally opposed design. The four finned cylinder barrels are separately mounted and each pair has a common cylinder head containing the valves and rocker gear. The firing order is 1 – 4 – 3 – 2. Minimum oil pressure at normal operating temperature is 28 psi at 2,500 rpm.