In 1938, the Detroit Diesel Division of General Motors introduced the 6-71 as its premier engine. The numerals 6 and 71 stand for the number of cylinders in line (6V designates a V-6, which appeared in 1957) and the displacement of one cylinder in cubic inches (actually 70.93 cubic inches). Every engine in the 71 series had a bore of 4.25 inches and a stroke of 5.0 inches. Tuned for commercial duty, it produced 165 horsepower. The battle-rated version made for the U.S. Navy developed 225 horsepower. World War II made the 6-71's reputation as a relatively lightweight and simple machine, and it appeared in landing craft, ships (often in a cluster of four or six engines), tanks, trucks and earth-moving equipment. Stan Grayson in his book Engines Afloat (www.devereuxbooks.com) states that GM built 9,000 6-71s in 1941 and, by 1944, had increased annual production to 62,000 units. That figure does not include the engines made for Gray Marine. The grand total for the war years was about 100,000 engines.