Armstrong Siddeley in Advertising
October 1927 and the new 15hp Armstrong Siddeley car was announced. This car was a direct development of the very successful 14/4 and though it still featured a flat radiator the big change was to use a six cylinder side valve engine.
Many other manufacturers had so equipped their cars and promoted the merits of the small capacity six cylinder engine. The main advantages were the inherent smoothness of a 'six-pot' engine and in the eyes of the public, for many makes of car, it represented a progression from the more common four cylinder engine.
Another benefit was the simplicity of maintenance in an era when the 'decoke' of a car engine, approximately every 10,000 miles, due to carbon build up was required. This was normally done by the local garage and the side valve configuration did not require the engine timing to be disturbed. This allowed for the work to be carried out by less qualified mechanics, resulting in lower garage charges. In short the move to a side valve engine was a market led decision.
In the advert above it is interesting to note the subtle change of emphasis directed towards the lady-driver.
Note the artist's impression of the Armstrong Whitworth, Siskin Mk IIIA, powered by the 450hp radial, Jaguar IVS engine. (The world's first supercharged aero engine)