title: Franklin O-540
text: # Franklin O-540
  
  The Franklin O-540 (company designation 8AC) was an American air-cooled aircraft engine that first ran in the early-1940s. The engine was of eight-cylinder, horizontally-opposed layout and displaced 540 cu in (9 L). The power output was nominally 300 hp (224 kW).
  
  ## Variants
  
  ### 8ACG-538 (XO-540-1)
  
      Geared propeller drive at 0.632:1, 300 hp (224 kW) at 3,200 rpm
  
  ### 8ACSA-538 (XO-540-7)
  
      Supercharged, 300 hp (224 kW)
  
  ### 8ACGSA-538 (XO-540-3/O-540-5)
  
      Supercharged and geared,330 hp (246 kW) at 3,200 rpm
  
  ## Applications
  
  * Northrop N-9M
  
  ## Specifications (8ACG-538/XO-540-1)
  
  Data from
  
  ### General characteristics
  
  * Type: 8-cylinder air-cooled horizontally opposed aircraft piston engine
  * Bore: 4.625 in (117.5 mm)
  * Stroke: 4.0 in (101.6 mm)
  * Displacement: 537.6 in³ (8.8 L)
  * Dry weight: 438 lb (199 kg)
  
  ### Components
  
  * Cooling system: Air-cooled
  
  ### Performance
  
  * Power output: 300 hp (224 kW) at 3,200 rpm
  