A bit more info., Rolls Royce designed the B range of engines in the mid 1940s as a power unit for various military vehicles, there was the B40 (4 cylinder) which was used in the Austin Champ, the B60 (6 cylinder) used in the Daimler Ferret, Humber Pig etc. and the B80 (8 cylinder) used in the Saladin and other heavy vehicles. A lot of the parts were common, like valves, springs, pistons, etc. so fewer spare parts were needed and broken vehicles could be used to repair others.