By Lloyd E. Stagner and TRAINS Magazine

With the ending of World War II in August 1945 and the accompanying drastic reduction in westbound freight tonnage, Nos. 2917-2929 were shifted to passenger service on Nos. 1-2 and 23-24, between Kansas City and Los Angeles, effective September 23. The 2-10-4's were now available for some Waynoka-Clovis freight work, replacing 4-8-4's. On the Plains Division, a reduction of helper service was effected as a 2-10-4 could handle 3800 tons out of Waynoka up Curtis Hill, compared with 2400 tons with a 4-8-4. Eastbound, from Canadian to Coburn, Tex., respective ratings were 5800 and 4500 tons on that ruling grade.

Before the spring-summer 1946 conversion of 10 FT diesels to passenger work, the 4-8-4's were assigned as follows on April 1: 2900-2916, Clovis-Argentine freight; 2917-2929 and 3765-3775, K.C.-L.A. passenger trains; 3776-3785, La Junta-Los Angeles passenger. Six 3751's were assigned to Argentine-Clovis freight, and the other 8 were in the K.C.L.A. passenger pool, usually handling the second sections of Nos. 3-4 and 23-24, which had been operated since 1943.

The 488 diesel units owned by AT&SF at the end of 1945 were the largest number on any railroad, but the company nevertheless embarked on an extensive program of improving steam power. All 2900's and the eight unequipped 3776's received Timken roller bearing side rods with needle bearings on the valve gear during 1946-1948. This improvement resulted in the maximum speed of these classes being increased to 100 mph. These engines also had either circulators or Duplex syphons in the firebox applied by 1952, increasing firebox heating surface to the equal of the 3765 class. Telescopic extension smokestacks were applied to all 4-8-4's, but the 3751's equipped with the flopover type retained them. Tender water level indicators and chassis lubrication were also included in this improvement program. The Santa Fe-designed Dutch oven oil burner system was applied; however, these burners proved troublesome to maintain owing to fire brick working loose in the pan, and they were subsequently removed.

New Worthington 6SA feedwater heaters were ordered for the 3751's not previously equipped, but three of these engines were retired with the Elesco equipment as this program was never completed.

As a result of the 1947 ICC signal order limiting passenger trains to 79 mph unless some form of automatic train stop or control was provided, AT&SF made extensive applications of ATS on most main lines, and 4-8-4's 3751, 3757-3760, 3776-3780, and 2900-2929 were equipped with Union Switch & Signal Company's intermittent ATS equipment, with the receiver mounted on the right trailer truck frame underneath the front axle, permitting timetable maximum speeds of 90 mph for the 3751's and 100 mph for the 2900's and 3776's. ATS equipment was added during 1950-1952 and removed for use on diesel locomotives when the steamers were retired.

The most extensive improvement project was the application of the Franklin Railway Supply Company's rotary cam poppet valve gear to No. 3752. The new built-up welded cylinders featured streamlined steam flow to and from the cylinders. A new front-end arrangement was used, with a longer stack extension with flared base. This arrangement permitted a less restricted gas flow from the flues to the stack. The application of circulators in the firebox instead of syphons also improved the drafting. Other improvements made to No. 3752 included a Worthington 6SA feedwater heater, chassis lubrication, lightweight piston, piston rods and crosshead, and the Dutch oven oil burner.

No. 3752 left the Topeka shop in February 1948 and was operated in both freight and passenger service west of Kansas City. In June, tests were operated with the dynamometer car, and at their conclusion, No. 3754 was tested on the same territory with similar trains in order to make a direct comparison between the two engines.

The comparative test was overwhelmingly in favor of 3752. Maximum indicated horsepower of 3754 was 3940 at 50 mph, whereas the poppet valve locomotive developed 4300 h.p. at 60 mph. Maximum drawbar horsepower at 50 mph increased from 3600 to 3910. In passenger service on trains Second 7 and 8, between La Junta and Kansas City, 3752 saved an impressive 18.42 per cent in fuel westbound and 18.71 eastbound. On fast freights between Argentine and Wellington, the reduction in fuel was 17.61 per cent westbound and 4.51 per cent eastbound.

Total cost of rebuilding No. 3752 was $43,153.68, and it was estimated this cost would be recovered in fuel and water savings in 77.7 months in freight and 54.2 months in passenger service. The test report was not released until August 29, 1949, and stated that even greater savings could be expected in freight service if the 5011-class 2-10-4's were equipped with poppet valves. Some steam supporters felt the test had been suppressed for 13 months because its publication would cast doubt on the wisdom of the accelerated diesel program which had started in 1949. However, by that year, Santa Fe was on the path toward complete conversion, and that course would not have changed by wholesale application of poppet valves. Perhaps, if poppet valves had been adopted before the war, dieselization would have slowed.