From the Rhinebeck website:
Country: Detroit, Michigan,
USA
Year: 1934
Horsepower: 210-240
R.P.M.: 2200
Weight: 415
Displacement: 668 cu. in.
Configuration: 7 cylinder radial, air cooled
Used in: Stearman PT-17, Waco UPF-7, N3N
Originating in the mid-thirties, the W-670 was updated through the Second World War and was widely used in primary training aircraft of the U.S. military. In the post-war years many were used in crop-dusters. A slightly different version of the W-670 was developed for use in tanks.