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Warner Scarab / R-420 / SS-50
Warner Super Scarab 185 / R-500 / R-550

Warner R-500 Super Scarab 165


First run in November 1927, the Warner Scarab is an American seven-cylinder radial aircraft engine, that was manufactured by the Warner Aircraft Corporation of Detroit, Michigan in 1928 through to the early 1940s. In military service the engine was designated R-420.


Warner Scarab engine advertisement for 1928 in Aero Digest


Amongst the many uses for the Scarab, the engine was fitted to the Cessna Airmaster and the Fairchild 24 (UC61 or Argus). Notably, in 1942, it was put into use powering the Sikorsky R-4, the first helicopter to be put into production.



Warner Scarab


The Warner 145 and 165 HP engines are the most commonly seen of the small radials for US-built pre-WWII era aircraft, in large part because of good parts availability due to the engines having been used on WWII Fairchild UC61s and Meyers OTWs.

Warner engines are also in demand as realistically sized, though far more powerful, replacement powerplants for many replica or restored World War I era airplanes which were originally fitted with rotary engines.


An air or hand-electric starter were available at extra cost.




A 7-cyl. air-cooled radial engine introduced in 1928, the Scarab developed 125 hp (93 kW) at 2,050rpm from 422 cu in (7 l) with a dry weight of 285 lb (129 kg).


Scarab Junior
A 5-cyl. version introduced in 1930 developing 90 hp (67 kW).
Super Scarab 165
Increased capacity 7-cyl engine developing 165 hp (123 kW) at 2,100rpm from 499 cu in (8 l) with a dry weight of 332 lb (151 kg).
Super Scarab SS-50
Alternative company designation for the Super Scarab.
Super Scarab SS-50A
A 145 hp (108 kW) de-rated Super Scarab.
Super Scarab 185
With the capacity increased further, developing 185 hp (138 kW) - 200 hp (149 kW) from 555 cu in (9 l).
Military designation of the Scarab
Military designation of the Super Scarab 165
Military designation of the Super Scarab 185
Alternative designation for the Warner Super Scarab SS-50A
Alternative designation for the Warner Super Scarab 165
Alternative designation for the Warner Super Scarab 185 (Primarily a helicopter application).


CAC Wackett
Cessna Airmaster
Cessna Model AW
Curtiss XC-10
Davis D-1
Faichild 22 C7E, C7F
Faichild 24 C8B (UC61 or Argus)
Fleet Model 1
Gee Bee Sportster
Harlow PJC-2
Meyers OTW
Monocoupe 110
Pasped Skylark
Ryan S-C
Ryan ST-W
Sikorsky R-4
Stinson SM-2
Waco RSO
Waco RBA
Waco BNF and RNF




Type: 7 cylinder, fxed radial, air cooled 4 stroke
Approved Type Certificate No.2
Military Rating: 110 hp at 1850 rpm
Commercial Rating: 110 hp at 1850 rpm
Displacement: 422
Compression ratio: 5.2-1
Bore: 4 1/4 in
Stroke: 5 1/4 in
Length: 29 in
Diameter: 35 1/2 in
Weight: 270 lb
Fuel consumption: not more than .55 lb/hp/hr
Oil consumption: not more than .025 lb/hp/hr
Lubrication: Force feed
Ignition: Dual Scintilla Magneto
Carburation: 1 Stromberg
Spark plugs: 2 per cylinder A.C.
Price: $2700

Scarab 50
Type: Seven-cylinder, air-cooled, radial piston engine
Bore: 4.25 in (108 mm)
Stroke: 4.25 in (108 mm)
Displacement: 422 cu in (6.92 L)
Length: 14 in (35.5 cm)
Height: 36.5 in (93 cm)
Dry weight: 292 lb (132.5 kg)
Valvetrain: 1 inlet and 1 exhaust valve per cylinder
Fuel system: 2 Stromberg carburetors
Fuel type: 67 octane Avgas
Oil system: Dry sump
Cooling system: Air-cooled
Power output: 125 hp at 2,050 rpm
Compression ratio: 5.15:1
Power-to-weight ratio: 0.43 hp/lb






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