The Alco 251 diesel engine

Diesel engine

A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...

 was developed by the American Locomotive Company

American Locomotive Company

The American Locomotive Company, often shortened to ALCO or Alco , was a builder of railroad locomotives in the United States.-Early history:...

 to replace the 244 and 539

ALCO 539T

The Alco 539T was a diesel prime mover built by the American Locomotive Company. This engine was also used as a stationary powerplant, used in pipeline pumping stations, tugboats and dredges. It has a straight six, four-stroke design in a cast block which produced from . The engine has a bore of...

. The 251 was developed to be used in diesel locomotives, as a marine power plant

Marine propulsion

Marine propulsion is the mechanism or system used to generate thrust to move a ship or boat across water. While paddles and sails are still used on some smaller boats, most modern ships are propelled by mechanical systems consisting a motor or engine turning a propeller, or less frequently, in jet...

 in ships and as a stationary power generator

Electricity generation

Electricity generation is the process of generating electric energy from other forms of energy.The fundamental principles of electricity generation were discovered during the 1820s and early 1830s by the British scientist Michael Faraday...

.

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

American Locomotive Company

The American Locomotive Company, often shortened to ALCO or Alco , was a builder of railroad locomotives in the United States.-Early history:...

'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

Turbocharger

A turbocharger, or turbo , from the Greek "τύρβη" is a centrifugal compressor powered by a turbine that is driven by an engine's exhaust gases. Its benefit lies with the compressor increasing the mass of air entering the engine , thereby resulting in greater performance...

, 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. A simple, safe design, it also offered a direct replacement for the aged 539 which was still used in switch

Switcher

A switcher or shunter is a small railroad locomotive intended not for moving trains over long distances but rather for assembling trains ready for a road locomotive to take over, disassembling a train that has been...

 engines and the ALCO RS-1

ALCO RS-1

The ALCO RS-1 was a 4-axle diesel-electric locomotive built by Alco-GE between 1941 and 1953 and the American Locomotive Company from 1953 to 1960. This model has the distinction of having the longest production run of any diesel locomotive for the North American market.The carbody configuration of...

 road switcher

Road switcher

A road switcher is a type of railroad locomotive used for delivering or picking up cars outside of a railroad yard. Since the road switcher must work some distance away from a yard, it needs to be able to operate at road speeds, it must also have high-visibility while it is switching, and it must...

. Like the 539, it was produced in Auburn, New York

Auburn, New York

Auburn is a city in Cayuga County, New York, United States of America. As of the 2010 census, the city had a population of 27,687...

. In August 1951 Alco built the ALCO DL420

ALCO DL420

The ALCO DL420 was the prototype ALCO S-5 switcher diesel-electric locomotive.It was built in August, 1951 using an early six cylinder 251 engine rated at and RS-3 subassemblies in its construction. It rode on two-axle trucks, having a B-B wheel arrangement, and was the first ALCO switcher with a...

 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

ALCO S-5

The Alco S-5 was a diesel-electric locomotive of the switcher type rated at , that rode on two-axle trucks, having a B-B wheel arrangement....

, a demonstrator and six units for the Boston and Maine were built. Two GE X3341 were built in 1954 for the White Pass and Yukon Route

White Pass and Yukon Route

The White Pass and Yukon Route is a Canadian and U.S. Class II narrow gauge railroad linking the port of Skagway, Alaska, with Whitehorse, the capital of Yukon. An isolated system, it has no direct connection to any other railroad. Equipment, freight and passengers are ferried by ship through the...

 with the 251 engines. In mid-1954 the Lehigh Valley

Lehigh Valley

The Lehigh Valley, known officially by the United States Census Bureau as the Allentown-Bethlehem-Easton, PA-NJ metropolitan area and referred to locally as The Valley and A-B-E, is a metropolitan region consisting of Lehigh, Northampton, Berks, and Carbon counties in eastern Pennsylvania and...

 supplied an FA-2 and FB-2 for installation of test 12 cylinder 251A engines. The Lehigh Valley units were tested for a year.

In 1954, the 251 went into production with the inline-6 at Auburn, New York

Auburn, New York

Auburn is a city in Cayuga County, New York, United States of America. As of the 2010 census, the city had a population of 27,687...

. The next year production of the V-12

V12 engine

A V12 engine is a V engine with 12 cylinders mounted on the crankcase in two banks of six cylinders, usually but not always at a 60° angle to each other, with all 12 pistons driving a common crankshaft....

 followed at Auburn, New York

Auburn, New York

Auburn is a city in Cayuga County, New York, United States of America. As of the 2010 census, the city had a population of 27,687...

 - where the 539 engine was built - and a V-16

V16 engine

A V16 engine is a V engine with 16 cylinders. Engines of this number of cylinders are uncommon in automotive use.A V16 engine is perfectly balanced regardless of the V angle without requiring counter-rotating balancing shafts which are necessary to balance Straight-4 and odd number of cylinder...

 version built at Schenectady, New York

Schenectady, New York

Schenectady is a city in Schenectady County, New York, United States, of which it is the county seat. As of the 2010 census, the city had a population of 66,135...

, replacing the 244.

Power generation

The inline-6 designs of 800 hp version of the 251 engine replaced the 539 engine in 1954 in Alco's low end line of power generation packages. The 244 engine was still used in higher end power generation packages until it too was replaced by 251 engined power generation equipment in 1956.

Ultimately a refined and successful design, the 251 outlived its designer. For a time it was built in Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

 by Montreal Locomotive Works

Montreal Locomotive Works

Montreal Locomotive Works was a Canadian railway locomotive manufacturer which existed under several names from 1883–1985, producing both steam and diesel locomotives. For a number of years it was a subsidiary of the American Locomotive Company...

. Today it is still available from Fairbanks-Morse

Fairbanks-Morse

Fairbanks Morse and Company was a manufacturing company in the late 19th and early 20th century. Originally a weighing scale manufacturer, it later diversified into pumps, engines, windmills, locomotives and industrial supplies until it was merged in 1958...

.

North American locomotive uses

Engine type	Power (hp)	| Locomotive(s)
inline-6 251	800	S-5 ALCO S-5 The Alco S-5 was a diesel-electric locomotive of the switcher type rated at , that rode on two-axle trucks, having a B-B wheel arrangement.... , GE 78 Ton, GE X3341.
inline-6 251A	900	S-6 ALCO S-6 The Alco S-6 was a diesel-electric locomotive of the switcher type constructed by ALCO of Schenectady, New York; a total of 126 locomotives were built between May 1955 and December 1960. The S-6 was a development of the earlier S-5; instead of the 800 hp ALCO 251 engine on the previous... .
inline-6 251B	900	S-6 ALCO S-6 The Alco S-6 was a diesel-electric locomotive of the switcher type constructed by ALCO of Schenectady, New York; a total of 126 locomotives were built between May 1955 and December 1960. The S-6 was a development of the earlier S-5; instead of the 800 hp ALCO 251 engine on the previous... , T-6 ALCO T-6 The Alco T6 was a diesel-electric locomotive of the switcher type rated at , that rode on two-axle trucks, having a B-B wheel arrangement.... .
inline-6 251C	1000	S-13, RS-23.
inline-6 251D	1200	DL535E, DL535EW.
V-8 V8 engine A V8 engine is a V engine with eight cylinders mounted on the crankcase in two banks of four cylinders, in most cases set at a right angle to each other but sometimes at a narrower angle, with all eight pistons driving a common crankshaft....  251F	1500	C415 ALCO Century 415 The ALCO Century 415 was a diesel locomotive of B-B wheel arrangement produced by the American Locomotive Company as part of their Century Series of locomotives.... .
V-12 V12 engine A V12 engine is a V engine with 12 cylinders mounted on the crankcase in two banks of six cylinders, usually but not always at a 60° angle to each other, with all 12 pistons driving a common crankshaft....  251B	1800	RS-11 ALCO RS-11 The ALCO RS-11 is a diesel-electric locomotive of the road switcher type rated at 1,800 hp , that rode on two-axle trucks, having a B-B wheel arrangement.-Development:... , RSD-12 ALCO RSD-12 The ALCO RSD-12 was a diesel-electric locomotive of the road switcher type rated at , that rode on three-axle trucks, having an C-C wheel arrangement.... , RS-18 MLW RS-18 The MLW RS-18 was an 1800 hp diesel-electric locomotive built by Montreal Locomotive Works between December 1956 and August 1968... , RS-36 ALCO RS-36 The ALCO RS-36 is a diesel-electric locomotive of which 40 were produced by ALCO between February 1962 and August 1963 for seven railroads.-Original Owners:-External links:* Sarberenyi, Robert. .... , FPA-4, FPB-4, DL500B ALCO DL500B The DL500B is an 1800 hp ALCo locomotive based on one of their "World Series" designs. The two Australian examples of this type of locomotive are the New South Wales Government Railways 44 class No.s 4401 - 44100 and the South Australian Railways 930 class.The NSWGR 44 class ALCo was used... .
V-12 V12 engine A V12 engine is a V engine with 12 cylinders mounted on the crankcase in two banks of six cylinders, usually but not always at a 60° angle to each other, with all 12 pistons driving a common crankshaft....  251C	2000	RS-32 ALCO RS-32 The ALCO RS-32 is a locomotive of which 35 were produced by ALCO between June 1961 and June 1962 for two customers: the New York Central Railroad and the Southern Pacific Company.... , C420 ALCO Century 420 The ALCO Century 420 was a four-axle, 2000 horsepower diesel locomotive of the road switcher type. 131 were built between June 1963 and August 1968. Cataloged as a part of ALCO's "Century" line of locomotives, the C420 was intended to replace the earlier RS-32 model.- Original Owners :Since... , MLW M420TR, M420W.
V-12 V12 engine A V12 engine is a V engine with 12 cylinders mounted on the crankcase in two banks of six cylinders, usually but not always at a 60° angle to each other, with all 12 pistons driving a common crankshaft....  251C	2150	DH643 ALCO DH643 The ALCO C-643DH, also known as the Century 643DH, was a twin-engine diesel-hydraulic locomotive, the first diesel-hydraulic road unit built in the United States. It had a C-C wheel arrangement and generated . Only three were built, all for Southern Pacific Railroad in 1964... .
V-12 V12 engine A V12 engine is a V engine with 12 cylinders mounted on the crankcase in two banks of six cylinders, usually but not always at a 60° angle to each other, with all 12 pistons driving a common crankshaft....  251E	2400	HR412.
V-16 V16 engine A V16 engine is a V engine with 16 cylinders. Engines of this number of cylinders are uncommon in automotive use.A V16 engine is perfectly balanced regardless of the V angle without requiring counter-rotating balancing shafts which are necessary to balance Straight-4 and odd number of cylinder...  251B	2400	RS-27 ALCO RS-27 The ALCO RS-27 is a diesel-electric locomotive built by ALCO between December 1959 and October 1962. Only 27 examples were manufactured. With ALCO's introduction of the Century Series line, the C-424 replaced the RS-27 in the builder's catalog... , RSD-15 ALCO RSD-15 The ALCO RSD-15 was a diesel-electric locomotive of the road switcher type built by ALCO of Schenectady, New York between August 1956 and June 1960, during which time 75 locomotives were produced... , RSD-17, C424 ALCO Century 424 The Century 424 was a four-axle, 2400 horsepower diesel locomotive of the road switcher type. 190 were built between April 1963 and May 1967. Cataloged as a part of Alco's Century line of locomotives, the C424 was intended to replace the earlier RS-27 model and offered as a lower-priced... , M424W.
V-16 V16 engine A V16 engine is a V engine with 16 cylinders. Engines of this number of cylinders are uncommon in automotive use.A V16 engine is perfectly balanced regardless of the V angle without requiring counter-rotating balancing shafts which are necessary to balance Straight-4 and odd number of cylinder...  251C	2500	C425 ALCO Century 425 The ALCO Century 425 was a four-axle, 2500 horsepower diesel locomotive of the road switcher type. 91 were built between October 1964 and December 1966.... .
V-16 V16 engine A V16 engine is a V engine with 16 cylinders. Engines of this number of cylinders are uncommon in automotive use.A V16 engine is perfectly balanced regardless of the V angle without requiring counter-rotating balancing shafts which are necessary to balance Straight-4 and odd number of cylinder...  251C	2750	C628 ALCO Century 628 The ALCO Century 628 was a six-axle, 2,750 horsepower diesel locomotive. 186 were built between December 1963 and December 1968. Cataloged as part of ALCO's 'Century' line of locomotives, the C628 was intended to replace the earlier RSD-15 model.... , C855 ALCO Century 855 The ALCO Century 855 was ALCO's most powerful diesel-electric locomotive and, at the time, the most powerful diesel locomotive ever built. Powered by a pair of 16 cylinder ALCO 251C diesel engines, and rated at , it was ALCO's answer to the EMD DD35 and the GE U50. The C855 rode on four two-axle... , C855B.
V-16 V16 engine A V16 engine is a V engine with 16 cylinders. Engines of this number of cylinders are uncommon in automotive use.A V16 engine is perfectly balanced regardless of the V angle without requiring counter-rotating balancing shafts which are necessary to balance Straight-4 and odd number of cylinder...  251E	3000	C430 ALCO Century 430 The ALCO Century 430 was a four-axle, 3000 horsepower diesel locomotive of the road switcher type. 16 were built between July 1966 and February 1968. Cataloged as a part of ALCO's 'Century' line of locomotives, the C430 was an upgraded version of the C425 model. Since 1992, 5 C430s have remained... , C630 ALCO Century 630 The ALCO Century 630 was a six-axle, 3000 horsepower diesel locomotive built between 1965 and 1967. 77 were built: 3 for Atlantic Coast Line Railroad, 4 for Chesapeake and Ohio Railway, 8 for Louisville and Nashville Railroad, 10 for Norfolk and Western Railway, 15 for Pennsylvania Railroad, 12... , C630M, M630.
V-16 V16 engine A V16 engine is a V engine with 16 cylinders. Engines of this number of cylinders are uncommon in automotive use.A V16 engine is perfectly balanced regardless of the V angle without requiring counter-rotating balancing shafts which are necessary to balance Straight-4 and odd number of cylinder...  251E	3600	C636 ALCO Century 636 The ALCO Century 636 was the most powerful single-engine diesel locomotive constructed by ALCO. The locomotive had a C-C wheel arrangement and . The locomotive rested on a pair of trucks of all-new design, known as the Hi-Ad, standing for 'high adhesion'. Visually, it is similar to the Century 630,... , M636.
V-16 V16 engine A V16 engine is a V engine with 16 cylinders. Engines of this number of cylinders are uncommon in automotive use.A V16 engine is perfectly balanced regardless of the V angle without requiring counter-rotating balancing shafts which are necessary to balance Straight-4 and odd number of cylinder...  251F	3700	LRC-2, LRC-3.
V-16 V16 engine A V16 engine is a V engine with 16 cylinders. Engines of this number of cylinders are uncommon in automotive use.A V16 engine is perfectly balanced regardless of the V angle without requiring counter-rotating balancing shafts which are necessary to balance Straight-4 and odd number of cylinder...  251G	3200	HR616 Bombardier HR-616 The Bombardier HR616, also known as the MLW HR616, was a 6 axle, freight locomotive manufactured in Montreal, Quebec, Canada. Twenty were built for Canadian National Railway in 1982, numbered 2100–2119, with 2100–2103 being temporarily renumbered as Bombardier 7000–7003, and rated at for... .
V-18 V18 engine A V18 engine is a V engine with 18 cylinders. A rare configuration not used in automobiles, large V18 diesel engines have seen limited use in mining, electricity generation, rail transport, and marine propulsion.- Examples of V18 engines :...  251	4000	M640.