The Lycoming R-680 is a nine-cylinder air-cooled radial engine, the first aero engine produced by Lycoming. The engine was produced in two types, the E and B series; both are essentially the same. The B4E was available in a trainer version with a front exhaust collector "ring" for use without cylinder air baffles.
R-680B4E
Rated at 225 hp (168 kW) at 2100 rpm.
R-680BA
Rated at 240 hp (180 kW)
R-680E3A
Rated at 285 hp (213 kW) at 2200 rpm.
R-680-6
Rated at 245 hp (183 kW)
R-680-13
Rated at 300 hp (220 kW) at 2200 rpm.
Beech AT-10 Wichita
Boeing-Stearman PT-13
Cessna AT-8/AT-17
Curtiss-Wright AT-9
Fleetwings BQ-2
Spartan NP-1
Stinson Airliner
Stinson Reliant
Stinson Vigilant
Waco S Series
Data from Jane's.
Type: Nine cylinder air-cooled radial
Bore: 4 5⁄8 in (117 mm)
Stroke: 4 1⁄2 in (114 mm)
Displacement: 680 in³ (11.15 litres)
Length: 37.5 in (953.1 mm)
Diameter: 43.5 in (1104 mm)
Dry weight: 515.46 lb (233.9 kg)
Valvetrain: One inlet and one exhaust valve per cylinder at 30 degrees.
Fuel system: single-barrel carburetor
Fuel type: 87 octane rating gasoline
Oil system: Full pressure type
Cooling system: Air-cooled
Power output: 330 hp (246 kW) at 2,300 rpm at sea level
Compression ratio: 7:1
Power-to-weight ratio: 0.64 hp/lb (1.05 kW/kg)
