The Liberty L-12 is an American water-cooled 45° V-12 engine, displacing 1,649 cubic inches (27 L) and making 400 hp (300 kW), designed for a high power-to-weight ratio and ease of mass production.

In May 1917, a month after the United States had declared war on Germany, a federal task force known as the Aircraft Production Board summoned two top engine designers, Jesse G. Vincent (of the Packard Motor Car Company) and Elbert J.

The Board brought Vincent and Hall together on 29 May 1917 at the Willard Hotel in Washington, where the two were asked to stay until they produced a set of basic drawings.

This led to Henry Leland leaving Cadillac to form the Lincoln Motor Company to make Liberty engines.

The two pieces formed the upper and lower halves of the completed assembly and were held together with a series of bolts running around the outside perimeter.

As was common for the era, the cylinders were separately formed from forged steel tubes with thin metal jackets surrounding them to provide cooling water flow.

Each camshaft was driven by a vertical driveshaft that was placed at the back of each cylinder bank, again identical to the Mercedes and BMW straight-six powerplants.

Fifty-two examples of a six-cylinder version, the Liberty L-6, which very closely resembled the Mercedes and BMW powerplants in overall appearance, were produced but not procured by the Army.

It was a 27 L (1,649 in3) engine with an output of 340 hp (250 kW; 340 PS), which was inadequate for the increasing vehicle weights as the war progressed and also suffered numerous problems with cooling and reliability.

The American version used an adaptation of the Liberty V-12 engine of 300 hp (220 kW), designed to use cast iron cylinders rather than drawn steel ones.

Inter-war, J. Walter Christie combined aircraft engines with new suspension design, producing a rapid and highly mobile tank.

Nuffield Liberty engines were used in British tanks of immediate pre-war and Second World War: HD-4 or Hydrodome number 4 was an early research hydrofoil watercraft developed by the scientist Alexander Graham Bell.

In the following twelve years, Wood built nine more Packard V-12 driven Miss Americas and broke the record five times, raising it to 124.860 miles per hour (200.943 km/h).

He also won five straight powerboat Gold Cup races between 1917 and 1921, and the prestigious Harmsworth Trophy nine times between 1920 and 1933, at the helm of his Miss Americas.