Hi Glaser,
In all probability this engine if a side valve as you say it is, would be from a Douglas Industrial Truck. Engines with the prefix letters of FT would be from examples of the Series 10 models which were produced under licence from Douglas by Withers (W.N.) Ltd of Wordsley, Stourbridge in Worcestershire. This particular series comprised of five models being;
a. Low loading Non-elavating
b. Low loading Elevating Platform
c. high loading Non-elevating
d. High loading Elevating Platform
e. The High Lift.
Fundamentally, the basic design of the Douglas Industrial Truck remains unaltered since its introduction to the public in 1928. The engine was based on the 596cc EW design and the first customers for the truck was the Great Western Railway using them at the Temple Meads, Bristol main station. Production took place before, during and after the Second World War. Eddie Withers became involved shortly before the Westinghouse take-over so I can imagine this particular engine FT3726 being manufactured possibly mid to late 1950's.
In the event other engines or crankcases come to light with numbers not recognised from normal motorcycle sequences below are prefix indentifications for reference purposes.
Engine Numbers
6R101 to 6R127
SR128 - 40 to SR421 -41 Models 5 and 6
1FT60 - 100 to 1FT60 to 125 - - - - - "- - - - -
Prefix 2FT Model 7
Prefix 4FT Model 8
Prefix 5FT Model 9
The wartime generating set 350cc ohv engines as mentioned by Chris would be prefixed FT35
Reg.
