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Gerald M. Best
Engine 1681 has acquired the "typical"
Southern Pacific look with boiler-tube
pilot and electric lights by the time of
this 1932 photo in Los Angeles. It still
uses saturated steam and has its original
square valve chests atop the cylinders.
This Mogul would be scrapped in 1935.

side and cross-section views of the
Economy valve chest conversion.
That SP look
New M-4s carried oil headlights atop
the smokebox, box types on the earli-
est engines and cylindrical ones later
on. Most had single-phase air compres-
sors on the right side ahead of the cab.
Wooden pilots with either vertical or
horizontal slats appeared on different
groups of engines. Train indicators
(the angled "number boards" beside
the smokestack) were early additions.
The engines always had steel cabs, but
originally with a narrow window ahead
of the wide one on each side.
Gerald M. Best In the 1920s the M-4s began to take
Also at Los Angeles in 1932, no. 1619 wasn't superheated but did have piston valves on what the road's fans now think of as
with new cylinders, as well as a larger tender with a narrow "clear vision" oil bunker. the "traditional" SP look. The compres-
sor moved to the left side and com-
Story continued from page 73 pound pumps replaced single-stage
as coal burners, but the SP began exper- inside Stephenson valve gear. How- types. Electric headlights replaced oil,
iments with oil fuel in 1895, and the M-4s ever, some Pacific Lines M-4s that relocated to the smokebox door on all
were soon converted to oil. weren't superheated also received pis- Pacific Lines and some T &NO engines.
Between 1919 and 1929, all of the ton valves, so the valves alone aren't a The standard SP boiler-tube pilot re-
T &NO engines and 24 on the Pacific reliable "spotting feature." placed the wooden "cowcatcher," and
Lines were given superheaters for Most M-4s received new cylinder the forward cab window was elimi-
more efficient operation with "drier," saddles with the valve conversion, but nated. The drawing depicts T &NO no.
hotter steam. Their engine weight a few got Economy valve chests bolted 448 after she was superheated in 1923.
increased to 147,910 pounds, with onto the square seats of their old slide- A small Vanderbilt tender is shown
127,650 pounds on drivers. Super- valve chambers. Engines 427, 446, and with the 448, but all M-4s came with
heated M-4s were re-equipped with pis- 1713 are shown with this variation in short rectangular tenders. Over the
ton valves, which were easier to lubri- Guy L. Dunscomb's A Century of South- years, the M-4s' fuel and water were
cate at highey temperatures. These ern Pacific Steam, published by the supplied by almost every kind of small
were still activated by the original author in 1963. Our drawings include SP road tender, including "haystack" or

76 AUGUST 1994