The Alco S-6 (specification DL 430) was a diesel–electric switcher locomotive constructed by ALCO of Schenectady, New York; a total of 126 locomotives were built between May 1955 and December 1960. The S-6 was an improved version of the earlier S-5 .

The Alco S6 (designed by the company as its DL430) was quite similar to all of its previous siblings, and as aforementioned was the successor to Alco's S5 design. The S5 was the first switcher to employ Alco's very own prime mover, the model 251A, which was capable of producing 800 horsepower via 6 cylinders.

The Alco S-6 (specification DL 430) was a diesel-electric switcher locomotive constructed by ALCO of Schenectady, New York; a total of 126 locomotives were built between May 1955 and December 1960. The S-6 was an improved version of the earlier S-5.

The Alco S6 was a diesel-electric switching locomotive, an updated version of the earlier S-5 model. A total of 126 were built at Alco's Schenectady, New York plant between 1955 and 1960. They were powered by a four-stroke diesel engine that gave them a maximum output of 900 horsepower and a top speed of 60 m.p.h.

Alco Reference #1 by Bob Liljestrand Brotherhood of Locomotive Firemen and Enginemen Magazine, October 1953

Alco Reference #1 by Bob Liljestrand Brotherhood of Locomotive Firemen and Enginemen Magazine, October 1953 Additions/corrections from: Howard Wise and Karl L. Swartz

It is indeed an Alco S6, ex Southern Pacific judging by the light package. This was one of Alco's last switcher models and only the SP really went for it. They bought 70 of the 126 examples built. I can think of about 4-5 examples that still exist in California, including one at PLA in Niles Canyon. Z

Alco S5, S6, SSB9 - Original Owners. by Robert Sarberenyi. S5: 8 US; S6: 93 US, 33 Mexico; SSB9: 2 US

Between 1955 and 1956 Espee receieved 70 Alco S-6 switchers. Two distinct varieties were delivered, #1033-1090 (later #1200-1257) were used as switcher, transfer and branchline units if photo captions are anything to go by.

The VE had numerous interesting locomotives over the years; this post will deal with the Alco S6 switcher. Alco built 126 S6's between 05-1955 and 12-1960. SP owned 70 of these 900 hp switchers that were powered by a turbocharged inline 6 cylinder prime mover.