Pratt & Whitney R-1860 Hornet B
The Pratt & Whitney R-1860 Hornet B was a relatively uncommon aircraft engine. It was a development of Pratt & Whitney's earlier R-1690 Hornet and was basically similar, but enlarged in capacity from 1,690 to 1,860 cubic inches (30.5 L).
Source: Wikipedia — Pratt & Whitney R-1860 Hornet B (CC BY-SA 4.0)