The Pratt & Whitney R-985 Wasp Junior is a nine-cylinder, radial, air-cooled aircraft engine known for its robust engineering and reliability. With a displacement of 985 cubic inches (16.1 L), it delivers a power output of 450 hp (336 kW) at 2300 rpm. This engine, designed for aviation applications, features a bore of 4.5 inches (114.3 mm) and a stroke of 5.5 inches (139.7 mm), with a compression ratio of 5.5:1. Its direct drive or geared transmission options and wet sump lubrication system contribute to its operational efficiency. The engine weighs approximately 650 lbs (295 kg) and utilizes aviation gasoline, typically with an 80/87 octane rating or higher, alongside dual magneto ignition.

This operation manual, written in English, provides comprehensive guidance for the Pratt & Whitney R-985 Wasp Junior engine. It covers essential information for operation, maintenance, and technical understanding, including oil capacity and recommended aviation-grade oil types. While specific service intervals are to be referred to within the manual, this document aims to assist owners, mechanics, and technicians in maintaining the engine's performance and longevity. The manual contains 217 pages of detailed technical specifications and operational procedures.