Three of the four SP M-K TE70-4S locomotives on their maiden run in March 1978
The M-K TE70-4S was a four-axle 2,800 hp (2.1 MW) B-B diesel-electric locomotive built by Morrison-Knudsen. The locomotive was a rebuild of the GE U25B with a Sulzer V-12 prime mover installed. Morrison-Knudsen rebuilt four for the Southern Pacific Railroad in 1978. The experiment proved unsuccessful and no additional units were rebuilt.
The prime mover for the M-K TE70-4S was a Sulzer 12ASV 25/30. Normally found in marine or stationary uses, the 12ASV 25/30 had been in production since 1969. The four-stroke turbocharged engine was rated for a maximum of 3,240 hp (2.4 MW) at 1000 RPM. The locomotives retained the GE GT598 D3A generators and GE 752 traction motors from the U25B. The capability of the prime mover notwithstanding, the locomotive was rated at 2,800 hp (2.1 MW).
The new prime mover required substantial alterations to the cab, carbody, and underframe. The locomotive measured 60 ft 2 in (18.3 m) long by 10 ft 7 1⁄2 in (3.2 m) wide, and stood 15 ft 10 7⁄8 in (4.8 m) high. It weighed 279,000 lb (126,552 kg).
Southern Pacific sent four GE U25Bs (Nos. 7030–7033), then at the end of their service life, to Morrison-Knudsen for rebuilding. Morrison-Knudsen rebuilt the four locomotives in its Boise, Idaho, shops in 1977–1978. The first revenue run occurred beginning March 1, 1978, when the four locomotives handled a Seattle–Los Angeles trailer-on-flatcar (TOFC) train between Portland and Los Angeles. Inauspiciously, one of the four locomotives broke down during the trip.
The locomotives carried a unique paint scheme featuring the red-and-orange of the SP's famed "Daylight" passenger trains, albeit in a different style. The color scheme led to the nickname "Popsicle"; unreliability led to their retirement in 1987.
- "News Photos". Pacific News. 18 (2): 28. February 1978. ISSN 0030-879X.
- "M-K's New TE50-4S unit". Pacific News. 19 (9): 4. September 1979. ISSN 0030-879X.
- Fearon, Joseph G. (1978). Application of Sulzer 12ASV 25/30 Diesel Engines to M-K TE70-4S Locomotives. Energy Technology Conference & Exhibition, Houston, Texas, November 5-9, 1978. American Society of Mechanical Engineers. pp. 1–12. 78-DGP-15.
- Guernsey, Paul; Immel, Ed; McKinley, Gene; Leeder, Bryan (March 1978). "Morrison-Knudsen-Built TE70-4S's Delivered to Espee" (PDF). The Trainmaster (211): 2.
- Lustig, David (May 2003). "Whatever happened to SP's 'Popsicles'?". Trains. 63 (5): 23. ISSN 0041-0934.
- Pinkepank, Jerry A.; Marre, Louis A. (1979). Diesel Spotter's Guide Update. Milwaukee, WI: Kalmbach Publishing. ISBN 0-89024-029-9.
- Liddle, S. G.; Bonzo, B. B.; Purohit, G. P.; Stallkamp, J. A. (1981). Future Fuels and Engines for Railroad Locomotives (PDF). 2. Pasadena, CA: Jet Propulsion Laboratory.
- Solomon, Brian (2014). GE and EMD Locomotives: The Illustrated History. Minneapolis, Minnesota: Voyageur Press. ISBN 978-0-7603-4612-9.