By the time cab units such as the F9 were built, railroads were turning to the road switcher-style of locomotive, as they had much better visibility from the cab without the need to lean out the window. The F9 was succeeded in most part by the EMD GP9.
The F9 used a 16-cylinder 567C series Diesel engine developing 1,750 hp (1.30 MW) at 800 rpm. The 567 was designed specifically for locomotive applications, being a 45 degree V-type two-stroke design, with 567 cu in (9.29 L) displacement per cylinder, for a total of 9,072 cu in (148.66 L). A D.C. generator powered four D37 traction motors, two on each Blomberg B truck. EMD has built all of its major components since 1939.
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An F9 can be distinguished reliably from a late F7 only by the addition of an extra filter grille ahead of the front porthole on the side panels on A units. Internally, the use of an 567C prime mover increased power to 1,750 hp (1.30 MW) from the F7's 1,500 hp (1.12 MW).
Marre, Louis A. (1995). Diesel Locomotives: The First 50 Years: A Guide to Diesels Built Before 1972. Railroad Reference Series. Waukesha, Wisconsin: Kalmbach Publishing. ISBN978-0-89024-258-2.
Solomon, Brian (2010). Vintage Diesel Power. Minneapolis, Minnesota: MBI Publishing. ISBN978-0-7603-3795-0.
Solomon, Brian (2011). Electro-Motive E-Units and F-Units: The Illustrated History of North America's Favorite Locomotives. Minneapolis, Minnesota: Voyageur Press. ISBN978-0-7603-4007-3.
Solomon, Brian (2012). North American Locomotives: A Railroad-by-Railroad Photohistory. Minneapolis, Minnesota: Voyageur Press. ISBN978-0-7603-4370-8.