Class P-1 (Locobase 5731) 
Data from set of DL&W locomotive diagrams at [external link] (29 October 2003). See also Robert A LeMassena, "The USRA HEAVY 4-8-2 and its Illustrious Ascendants", Railway & Locomotive Historical Society Newsletter (Vol 23, #2 - Spring 2003). Works numbers were 65418-65422 in March 1924. Works numbers were 65418-65422 in March 1924.
Firebox heating surface included 35 sq ft (3.25 sq m) of arch tubes. Each cylinder was fed through relatively small 11" (279 mm) piston valve.
Drury (1993) says these five Mountains (the first on the line) were bought to eliminate double-heading passenger trains on the grades east of Scranton, PA. But they were soon relegated to local service because of their lack of speed.
When the Atlantic Coast Line found itself short of power in World War II, the Lackawanna realized it could spare this class. As the J-1s, these were put in service between Tampa, Fla and Albany, Ga until their retirement in 1951-1952.
Class P-2/P-3 (Locobase 203)
Data from tables in 1930 Locomotive Cyclopedia. See also DL&W 7 - 1933 Locomotive Diagrams supplied in May 2005 by Allen Stanley. (Thanks to Chris Hohl for his 11 November 2012 email noting a discrepancy in road numbers.) Works numbers were 66163-66164 in April 1925 and 66428-66430 in September.
Water-tube firebox. Three-cylinder passenger locomotive, two with Baker gear (P-2), three with Walschaert (P-3). Followed two years later by heavier, low-drivered freight version (Locobase 2230) with lots of tractive effort, but much lower adhesive factor.
According to Farrington (Railroading Coast to Coast, 1976), the DL&W's Scranton Shops removed the center cylinder in 1940. Drury, 1993, says this occurred much earlier, in 1930-1931 and the two cylinders were enlarged to 28" x 32" (711 x 813 mm). The locomotive diagrams confirm Drury and show also that, as modified, 1450 and 1452 had 11" (279 mm) piston valves and 1451, 1453-1454 had 14" (356 mm) piston valves. All of the engines used Walschaert gear at that point, but the P-2's (1450-1451) valve travel measured 7 1/2" (191 mm) while the P-3a valves traveled 9" (229 mm).
Class P-4/P-5 (Locobase 202)
Data from tables in 1930 Locomotive Cyclopedia and DL&W 7 - 1933 Locomotive Diagrams supplied by Allen Stanley in May 2005 Works numbers were 66954-66964 in September; 66965-67524 in October, and 67525 in November.
Firebox heating surface are included 80 sq ft (7.43 sq m) in Superior E-type thermic syphons and 24 sq ft (2.23 sq m) . Low-drivered, three-cylinder locomotive with a low adhesive factor. The two outside cylinders had 32-in strokes and drove the third axle while the inside cylinder had a 28-in stroke powering the second axle. This class followed a high-drivered (73") class in which all three cylinders had the same length stroke. The three cylinders each had a 12" (305 mm) piston valve.
Because these freight locomotives put less demand for maintenance on that hard-to-get-at center cylinder, the Lackawanna left the arrangement intact throughout the class's lifetime. Retirement came in 1946-1950.
