The Liberty L-4B was an experimental water-cooled inline four-cylinder aircraft engine developed in the United States during World War I.

[1] The 102 hp (76 kW) engine was designed and manufactured by the Hudson Motor Car Company and was mainly intended for use in training airplanes.

[2] Only two examples of the L-4B were produced, since other types of engines were available and in production.

While the engine was ground-tested, it is unknown if the L-4 was ever test-flown.

Related lists This article incorporates text from Liberty L-4, a public domain work of the United States Government.