Southern Pacific class MC-4

4 ft 8+1⁄2 in (1,435 mm) standard gaugeDriver dia.57 in (1,448 mm)Adhesive weight398,500 lb (180,800 kg)Loco weight432,600 lb (196,200 kg)Boiler pressure200 psi (1.4 MPa)High-pressure cylinder26 in × 30 in (660 mm × 762 mm)Low-pressure cylinder40 in × 30 in (1,016 mm × 762 mm)

Performance figures
Tractive effort	85,040 lbf (378.28 kN)

Career
Operators	Southern Pacific Railroad
Class	MC-4
Numbers	4017 – 4028
First run	July 21, 1911
Retired	1947 – 1948
Disposition	scrapped

Southern Pacific Railroad's MC-4 class of steam locomotive was the second class ordered and built as cab forward locomotives. Southern Pacific (SP) found the MC-2 class sufficient for a proof-of-concept for cab forward locomotives and sought to continue with now tested designs.

In service, SP found that the locomotives were a little too slow for the traffic needs. By 1930, all of the MC-4 class had been "simpled" to use uniform size cylinders and feedwater heaters were installed to address the issue. They were then reclassified as AC-2 locomotives. As rebuilt, the locomotives continued in service through the end of World War II.

References

• Diebert, Timothy S. & Strapac, Joseph A. (1987). Southern Pacific Company Steam Locomotive Conpendium. Shade Tree Books. ISBN 0-930742-12-5.