title: Franklin O-175
text: # Franklin O-175
  
  The Franklin O-175 (company designation 4AC-176) was an American air-cooled aircraft engine of the 1940s. The engine was of horizontally-opposed four-cylinder and displaced 175 cu in (2.9 L). The power output was nominally 80 hp (60 kW). A later variant was designated O-180, despite sharing the same displacement.
  
  A related four-cylinder engine of slightly smaller capacity was known as the O-170 or 4AC-171. It produced 60 hp (45 kW).
  
  ## Variants
  
  ### O-170
  
  **4AC-171**
  
  
      60 hp (45 kW)
  
  ### O-175
  
  **4AC-176**
  
  
         4AC-176-B - 65 hp (48 kW) at 2,200 rpm
         4AC-176-BA/(O-175-1) - 65 hp (48 kW) at 2,300 rpm
         4AC-176-C - 75 hp (56 kW) at 2,500 rpm
         4AC-176-D - 80 hp (60 kW) at 2,650 rpm
         4AC-176-F - 80 hp (60 kW) at 2,500 rpm
  
  ## Applications
  
  * Aeronca L-3D
  * Bowyer BW-1 flying wing
  * CAP-4 Paulistinha
  * Harris Little Jewel
  * Interstate Cadet
  * IPT-7 Junior
  * Jensen Sport (O-170)
  * Johnson-Funke monoplane
  * Langley Twin
  * Piper J-3 Cub
  * Piper J-4
  * Piper L-4
  * Porterfield Collegiate
  * Taylorcraft BF-60 (O-170)
  * Taylorcraft BF-65
  
  ## Specifications (4AC-176-BA2, O-175-1)
  
  Data from Wilkinson
  
  ### General characteristics
  
  * Type: 4-cylinder air-cooled horizontally opposed aircraft piston engine
  * Bore: 4 in (102 mm)
  * Stroke: 3.5 in (89 mm)
  * Displacement: 176 cu in (2.88 L)
  * Length: 28.6 in (726 mm)
  * Width: 30.2 in (767 mm)
  * Height: 20 in (508 mm)
  * Dry weight: 182 lb (82.6 kg)
  
  ### Components
  
  * Valvetrain: OHV, 1x inlet valve, 1x exhaust valve operated by pushrods
  * Fuel system: 1x Marvel-Schebler MA-3P updraught carburetor
  * Fuel type: 73 octane gasoline
  * Oil system: Pressure system at 40 psi (3 bar), wet sump
  * Cooling system: Air-cooled
  
  ### Performance
  
  * Power output: 65 hp (48.5 kW) at 2,300 rpm for take-off
  * Specific power: 0.37 hp/(cu in) (16.837 kW/L)
  * Compression ratio: 6:1
  * Specific fuel consumption: 0.49 lb/(hp h) (0.298 kg/(kW h), 220 US gal/(hp h)) cruising
  * Oil consumption: 0.003 lb/(hp h) (0.0018 kg/(kW h), 1.4 US gal/(hp h)) cruising
  * Power-to-weight ratio: 0.357 hp/lb (0.587 kW/kg)
  