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-680B4ERated at 225 hp (168 kW) at 2100 rpm.
R-680BARated at 240 hp (180 kW)
R-680E3ARated at 285 hp (213 kW) at 2200 rpm.
R-680-6Rated at 245 hp (183 kW)
R-680-13Rated at 300 hp (220 kW) at 2200 rpm.
Beech AT-10 WichitaBoeing-Stearman PT-13Cessna AT-8/AT-17Curtiss-Wright AT-9Fleetwings BQ-2Spartan NP-1Stinson AirlinerStinson ReliantStinson VigilantWaco S SeriesData from Jane's.
Type: Nine cylinder air-cooled radialBore: 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 carburetorFuel type: 87 octane rating gasolineOil system: Full pressure typeCooling system: Air-cooledPower output: 330 hp (246 kW) at 2,300 rpm at sea levelCompression ratio: 7:1Power-to-weight ratio: 0.64 hp/lb (1.05 kW/kg) 
