Continental A-40, Horizontally-Opposed 4 Engine


Display Status:

This object is on display in the Barron Hilton Pioneers of Flight Gallery exhibition at the National Air and Space Museum in Washington, DC.

Collection Item Summary:

Once the largest independent manufacturer of automotive engines, Detroit’s Continental Motors purchased the rights to a single-sleeve valve engine design in 1925, believing this technology might replace poppet valves in aircraft engines. However, after considerable testing the company only became successful in aviation after reverting to poppet valves and production of four cylinder horizontally opposed engines. The Continental A-40 was the predecessor of a long line of successful horizontally-opposed Continental engines built for general aviation and military aircraft.

For example, the Continental A-40 made the classic Piper J-3 Cub possible, and powered other aircraft such as the Taylor Cub E-2 and Taylorcraft Model A.

An advantage of horizontally-opposed engines is better forward visibility than radial or V-type engines. Today opposed engines have replaced all other types of piston engines for various reasons, including fewer cylinders for equal power and smooth running. And Continental is one of the world’s largest manufacturers of general aviation engines.

Collection Item Long Description:



Inventory Number


Physical Description

  • Type: Reciprocating, 4 cylinders, horizontally-opposed, air-cooled
  • Power rating: 29.8 kW (40 hp) at 2,575 rpm
  • Displacement: 1.9 L (115 cu in.)
  • Bore and Stroke: 79 mm (3.1 in.) x 95 mm (3.8 in.)
  • Weight: 69.9 kg (154 lb)
  • Manufactured circa 1931
  • Has propeller hub; air-cooled; missing 1 spark plug, data plate, manifold

Credit Line

Donated by Robert B. Meyer Jr.


Country of Origin

United States of America




Length 70.9 cm (27.9 in.), Width 67.1 cm (26.4 in.), Height 51.8 cm (20.4 in.) (dimensions for Continental A-40-5)

Data Source

National Air and Space Museum

Restrictions & Rights

Do not reproduce without permission from the Smithsonian Institution, National Air and Space Museum


PROPULSION-Reciprocating & Rotary