Curtiss K-12 By Note: This item is currently in storage. The Curtiss K-12 was a milestone in the development of liquid-cooled aircraft engines and was regarded as one of the most advanced in the world for its time. Designed by Charles B. Kirkham and first tested in 1916, the K-12 featured a cast aluminum upper crankcase and integral cylinder blocks, four valves per cylinder, and "wet sleeve" construction for improved cooling. It relied upon high rpm and reduction gearing to develop the same power as larger engines. Although technologically advanced, many of the K-12's innovations challenged the state-of-the-art and created serious reliability problems. The K-12 design, however, led to the development of the very successful Curtiss D-12 (1922) engine used in fighters and racing planes. By 1926 the D-12 design had evolved into the more powerful Curtiss V-1570 Conqueror, noted for its use in military aircraft. That evolution was continued in the powerful liquid-cooled, V-12 aircraft engines of World War II that owed so much to design concepts pioneered in the K-12 engine of 1916. TECHNICAL NOTES: Type: 12-cylinder, liquid-cooled, Vee Displacement: 1,145 cu.in. Rated hp: 375 Rated rpm: 2,250 Click here to return to the Featured Accessions index. Find Out More Related Fact Sheets Curtiss D-12 Engine Curtiss V-1570 Conqueror Engine Note: The appearance of hyperlinks does not constitute endorsement by the National Museum of the USAF, the U.S. Air Force, or the Department of Defense, of the external website, or the information, products or services contained therein.