The Armstrong Siddeley 12 Plus

Production period	1936 to 1939
Number of cars produced	3,750
Engine	6 cylinder, 1666cc, 45bhp

The 12+ was produced between 1936 and 1939, with a total production of 3,750 vehicles (which includes the 14).

In 1935 the 12HP was complimented by a model with increased power, being known at first as the 12+ (Twelve Plus). A change was made to the pushrod overhead valves, now being slightly inclined and fed by a horizontal carburettor through an alloy manifold. The cylinder bore was now 61mm with the 95.2mm stroke still being retained from the 12 engine resulting in an engine capacity of 1666cc that provided 45bhp.

Wheelbase was lengthened to 9’ 0” and the chassis was now a box section. The differential ratio was altered to 5.3 to 1 and larger tyres were fitted allowing easier running at touring speeds.

In 1936 a centrifugal clutch was fitted as a further refinement and the car then became known as the 14.