Coolspring Spotlight: Circa-1908 6 hp Callahan Engine

By Staff
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The circa-1908 6 hp Callahan on display at the Coolspring Power Museum.
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Identification plate for the circa-1908 6 hp Callahan.
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The circa-1908 6 hp Callahan came with both hit-and-miss and throttle-style governors.
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A rear view of the camstopper camshaft.
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A front view of the camshaft.

Manufacturer: W.P. Callahan & Co., Dayton, OH
Serial number: 3179
Horsepower: 6 hp
Bore & stroke: 5-3/4in x 10in
Ignition: Make-and-break
Governing: Hit-and-miss
Owner: Coolspring Power Museum

This is a circa-1908 6 hp Callahan cam-stopping engine built by the W.P. Callahan & Co. of Dayton, Ohio. The company, founded by William P. Callahan about 1896, produced high-grade gas engines in sizes from 4 hp to 100 hp. “Regardless of their size, they retained almost identical proportions and design features,” says Coolspring Power Museum president Clark Colby. Callahan engines were designed around patents issued to Peter T. Coffield (formerly associated with the Springfield (Ohio) Gas Engine Co.) and Edward E. Williams. Callahan engines remained in production until approximately 1915.


This engine came with both hit-and-miss and throttle-style governors. If you ordered the hit-and-miss governor, which this example has, you got a centrifugal governor driven by the crankshaft timing gear at the back of the engine, which functioned to stop the action of the entire sideshaft when the engine came up to speed. When the engine slows down, the governor re-engages the camshaft at the right place and the mechanically operated exhaust, intake and fuel valves operate as expected, as does the igniter in the head, causing the engine to fire again. Callahan engines featured sideshaft-actuated intake, exhaust and fuel valves and an exhaust-ported cylinder.


This particular engine was obtained from another collection and no further information is available. It was brought to Coolspring in 1992.

Want to learn more about this engine and 38 others? Check out Coolspring: Discovering America’s Finest Antique Engine Museum and see them run on the Coolspring Museum DVD.

Visit Coolspring Power Museum for more information about exhibits of early stationary internal combustion engines and events held at the museum.

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