First introduced in 1920, all Alvis cars made in the early 1920s were designed around a four-cylinder engine. They proved to be a popular sports car but GT Smith-Clarke, the chief design engineer was looking for better performance so in 1927 he introduced an 1870cc six-cylinder overhead valve engine and it was this engine and all future enlarged versions of this engine which powered most of the cars Alvis made right up to the outbreak of World War II in 1939.
To increase performance, over time, the original 1870cc engine was bored out and given a longer stroke so that it grew from 1870cc, first to 2148cc and then to 2511cc. This engine was the one used in the Speed Twenty – a name derived from the official British RAC rating – which was introduced in 1931. The Alvis Speed Twenty stayed in production from 1932 to 1935 and was a low-slung car with excellent road manners and an attractively styled body. The radiator carried the red triangular badge which distinguished all Alvis vehicles.
The Alvis Speed Twenty had a front-mounted engine which drove the rear wheels. This engine had a bore and stroke of 73 mm x 100 mm and it developed 65kW at 4000rpm. Fuel was supplied through three horizontal SU carburettors giving the car a top speed of 142 km/h. Suspension, front and rear, consisted of a beam axle and various body styles were offered.
During its production life 1165 examples were built varying from sports cars to saloons making the Speed Twenty, available in four sub types, all of them with triple SU carburettor engines, the highest selling pre-war car produced by Alvis. By the mid-1930s the Speed Twenty had reached its highest level of maturity and it was finally overtaken by a larger model with a next generation six-cylinder engine with a capacity of 3.5 litres.