The Avia M 337 (originally designated the Walter M337) is an inverted six-cylinder air-cooled inline engine. It was developed by the Czechoslovak company as a six-cylinder derivative of the four-cylinder M 332 engine, going into production in 1960. An unsupercharged version of the M 337 is designated M 137. Production transferred to Avia in 1964, and to Letecke Opravny Malesice (LOM) in 1992.
M 337ABasic supercharged engine - not rated for aerobatics
M 337RModified for pusher installation
M 337AKmodified oil system for unlimited inverted flying. "Snap" aerobatics permitted.
M 337AK1AK fitted with alternator instead of generator
M 337BIncreased max running speed (3000 rpm) - increased power - 173 kW (235 hp).
M 337BKAerobatic version of B.
M 337CIncreased compression ratio - 185 kW (252 hp)
M 137AUnsupercharged version of M 337 - 134 kW (180 hp) take-off power. Aerobatics allowed.
M 137AZAs M 137A, with filtered air feed
AeroVolga LA-8CFalconar SAL MustangLet L-200 MoravaZlín Z 526, Z 726Zlín 142Zlín Z 43Data from Jane's All The World's Aircraft 1980-81
Type: 6-cylinder inverted air-cooled supercharged inline engineBore: 105 mm (4.13 in)Stroke: 115mm (4.53 in)Displacement: 5.97 L (364.3 in³)Length: 1,410 mm (55.51 in)Width: 472 mm (18.58 in)Height: 628 mm (24.72Dry weight: 148 kg (326.3 lb)Valvetrain: two camshaft operated valves per cylinder, sodium filled exhaust valveSupercharger: CentrifugalFuel system: Low-pressure fuel injectionFuel type: Min 72-78 OctaneOil system: Dry sump pressure feed systemCooling system: Air-cooledPower output: 157 kW (210 hp) at 2,750 rpm (take-off) 
