Alvis' entry into car manufacture came with the 10/30 in 1920. This was a high quality light car with a four-cylinder fixed head monobloc side valve engine of 65 x 110 mm, 1460 cc. A three bearing crankshaft was used, carried in an aluminium crankcase bolted to the cast iron block, with a separate four-speed right hand change gearbox, at a time when these features were unusual in light cars. All of the mechanical parts were of Alvis design and manufacture. Wheelbase was 9'2" and steel artillery wheels were standard. Maximum speed was some 60 mph. In 1921 the range was extended to include the 68 x 110 mm, 1598 cc 11/40, a model more sporting in character offered either on the previous chassis or with a shorter, 9'0½" wheelbase, and this was renamed the 12/40 in 1922.

1922 10/30 Cross & Ellis 2 - seater

Next year a 9'4½" wheelbase version appeared. The chassis was of conventional design for the period, with half-elliptic springs all round and beam axles, the engine and gearbox being carried in a subframe. Alvis designed brakes operated on the rear wheels only. From the very start, Alvis fitted their own design of cast aluminium rear axle, with fully floating halfshafts. Despite many detail design changes and the use of many different final drive ratios, this axle remained a recognisable feature of most Alvis cars until 1940. A worm and wheel steering box of Alvis' own design and manufacture was employed, giving the customary high gearing of the vintage period. It is believed that upwards of 2,700 side valve Alvises were made but only a handful exist today.

1922 11/40 Cross & Ellis Tourer

They were discontinued in 1925 in favour of the overhead valve 12/50 when the success of the latter demanded all the company's resources. At this time the majority of the cars produced had open coachwork, most of the 10/30s were two seaters, some more sporting than others, but the 11/40 and 12/40 also appeared in four seater tourer and saloon incarnations. The rakish "ducks-back" polished aluminium (usually) sports 2 seater body, so called from the shape of the pointed tail with spare wheel underneath, made its appearance very early on.

1923 12/40 Carbodies saloon