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ALCO 251

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The Alco 251 diesel prime engine was developed by the American Locomotive Company to replace the 244 and 539. The 251 was developed to be used in diesel locomotives, as a marine power plant in ships and as a stationary power generator.

Development

Development was initiated in 1949, and like the 244 would have a bore (cylinder diameter) of 9 inches (229 mm), and a stroke of 10.5 inches (267 mm). Its designation combines Alco's identifier for that bore and stroke - 2 - with the year its design was approved for laboratory testing - 1951. Chief Engineer of Diesel Engine Design, Paul Vaughan, designed the 251 to improve upon the major weaknesses of the 244. A wet block design was used to address severe thermal differences which existed in the dry block 244. The welded block and base was kept, as was the four-point mounting. New in the 251 was an aftercooler for the turbocharger, which minimized temperature differentials but also benefitted performance. Many small improvements were made to the crankshaft, bearings, pistons, injectors and camshafts.

To avoid the problems caused by rushing the 244 into production, the 251 was put through an extensive testing process.

The 251 engines first installed in locomotives for testing were inline-6 designs of 800 hp (597 kW). A simple, safe design, it also offered a direct replacement for the aged 539 which was still used in switch engines and the ALCO RS-1 road switcher. Like the 539, it was produced in Auburn, New York. In August 1951 Alco built the ALCO DL420 test unit with a six cylinder 800 horsepower 251 engine. Ten GE 78 Ton units followed in mid 1953 and were exported to the Consolidated Railroads of Cuba. The following year seven ALCO S-5 and two GE X3341 were built for the White Pass and Yukon Route. In mid-1954 the Lehigh Valley supplied an FA-2 and FB-2 for installation of test 12 cylinder 251A engines.

In 1954, the 251 went into production with the inline-6 at Auburn, New York. The next year production of the V-12 followed at Auburn, New York - where the 539 engine was built - and a V-16 version built at Schenectady, New York, replacing the 244.

Ultimately a refined and successful design, the 251 outlived its designer. For a time it was built in Canada by Montreal Locomotive Works. Today it is still available from Fairbanks-Morse.

North American Locomotive Uses

Engine type Power (hp) Locomotive(s)
inline-6 251 800 S-5.
inline-6 251A 900 S-6.
inline-6 251B 900 S-6, T-6.
inline-6 251C 1000 S-13, RS-23.
inline-6 251D 1200 DL535E.
V-8 251F 1500 C415.
V-12 251B 1800 RS-11, RSD-12, RS-18, RS-36, FPA-4, FPB-4, DL500B.
V-12 251C 2000 RS-32, C420, M420W, HR412.
V-12 251C 2150 DH643.
V-16 251B 2400 RS-27, RSD-15, RSD-17, C424.
V-16 251C 2500 C425.
V-16 251C 2750 C628, C855, C855B.
V-16 251E 3000 C430, C630, M630.
V-16 251E 3600 C636, M636.
V-16 251F 3700 LRC-2, LRC-3.
V-16 251G 3200 HR616.
V-18 251 4000 M640.
  • Pinkepank, Jerry A. (1973). The Second Diesel Spotter's Guide. Milwaukee, Wisconsin: Kalmbach Publishing. ISBN 978-0-89024-026-7.
  • Steinbrenner, Richard T. (2003). The American Locomotive Company - A Centennial Remembrance. Warren, NJ: On Track Publishers, LLC. ISBN 0-911122-07-9