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The Napier Lion Aircraft Engine

The Napier Lion was a 12-cylinder aircraft engine produced by Napier & Son from 1917 until the mid 1930's. Although initially intended as an aircraft engine as it was the most powerful engine of its day it was used to power John Cobb's Railton Mobil Special in 1947 too 394 mph, a new car Land Speed Record which was not beaten until the 1960's, supercharged racing versions of the engine exceeded 1300hp output. The advanced design of the Lion resulted in an extended production period.

Napier Lion 1b Aircraft Engine


The Engine had an unusual cylinder layout with three banks of cylinders, these were in a trident arrangement (two banks in a wide V and the third bank in the middle of them). The Napier Lion engine's construction was also for it's time, it had a one-piece aluminium block machined from a single billet, each cylinder had four valves and each of the three banks of cylinders had twin overhead camshafts.

Aircraft that used the Napier Lion aero-engine

Alliance P.2 SeabirdAvro BisonBlackburn Blackburn
Blackburn DartBlackburn PelletBlackburn Ripon
Blackburn VelosBoulton Paul AtlanticBoulton Paul Bodmin
Boulton Paul BoltonFairey IIIFairey Fawn
Gloster GorcockGloster GuanHandley Page Harrow
Handley Page HyderabadMitsubishi B1MParnall Pike
Parnall PossumParnall PuffinSupermarine S.4
Supermarine S.5Supermarine SeagullSupermarine Southampton
Tarrant TaborVickers VernonVickers Valparaiso
Vickers VictoriaVickers VirginiaVickers Vixen
Westland Walrus  

Napier Lion II Specifications:

  • Type: 12-cylinder water-cooled (3 banks of 4 cylinders) piston engine with four valves per cylinder and two double overhead camshafts on each of the three banks of cylinders
  • Bore: 5.5 in (139.7 mm)
  • Stroke: 5.125 in (130.17 mm)
  • Displacement: 1,461.6 in³ (23.9 L)
  • Length: 57.5 in (1460 mm)
  • Width: 42.0 in (1067 mm)
  • Height: 43.5 in (1105 mm)
  • Dry weight: 960 lb (435 kg)
  • Cooling system: Water-cooled
  • Power output: 480 hp (358 kW) at 2,200 rpm at 5,000 ft
  • Specific power: 0.32 hp/in³ (15.0 kW/L)
  • Compression ratio: 5.8:1

Napier Lion VII Aircraft Engine

Napier Lion VII aircraft engine

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These pictures of a Napier Lion are Copyright © June 2014 Siteseen Ltd. We only authorise non-commercial picture use and particularly encourage their use for educational purposes. These Napier Lion pictures are not in the Public Domain.

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Napier Lion Aircraft Engine picture and Specifications


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