[johnbuckley]

the so-called 14.9 hp of the small bore engine was the "fiscal" or RAC rating horsepower. this was ((diameter of cylinder in inches ) squared x the number of cylinders )all divided by 2.5 . This formual was devised in 1909 by the Royal Automobile Club and gave at the time a good approximation of the horsepower on an internal combustion engine. Of course engine design improved and the formula was no longer a good approximation but the UK goverments of the times kept using it until 1947 as a basis for an annuala road tax levy on vehicles . This gave rise to the Model A 3.3 litre (200 cu in)engine being rated in the UK for tax purposes at 24hp using RAC formula, whist actually producing 40 bhp ,( both large bore and small bore engines were available in the Model A's later years) . Furthermore other European countries used a similar but not identical system for annual vehicle tax. Thus ( from Sam Roberts book History of the Y and C) the European Ford Y was actually producing 22 bhp, but was rated in UK for tax at at 8 hp, in France at 6CV ( chevalvapeur) and in Germany at 4 PS (pfered starke).