Franklin 4AC

4AC
Franklin O-200 at the Hiller Aviation Museum
Type	Flat-4
Manufacturer	Franklin Engine Company
First run	1938

The Franklin 4 (US military designations O-150, O-170, O-175, and O-200) was a series of air-cooled aircraft engines of flat-4 configuration produced in the 1930s and 1940s.

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(4AC-176-BA3 identical except for electric starter and generator)

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Wikipedia