ALCO HH Series - HH660

The HH660 started production in ALCO's lineup in October 1938; 43 examples were built until April 1940. It utilized a naturally aspirated version of the 6-cylinder McIntosh and Seymour 538 engine, producing 660 hp (490 kW). Externally, HH660s are indistinguishable from late HH600s.

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