3.5 Litre

The 3½ Litre (SA 25.63 hp) was introduced at the 1935 Motor Show for the 1936 model year and marked a move ‘up-market’ by Alvis, being available as a “chassis only”.  Series built standard bodies were not offered and at least 12 coachbuilders produced bodies on the 62 chassis eventually  completed. Technically, the chassis closely resembled the SC and SD Speed Twenties, but with the wheelbase extended to 10’ 7” whilst retaining the transverse leaf independent front suspension and the SD Speed Twenty rear springs. The six cylinder engine was Alvis-like in appearance with cast iron cylinder head and block mounted on an aluminium crankcase but with cylinder dimensions increased to 83 x 110 mm for 3,571 cc. For the first time a massive seven bearing crankshaft was used, with a friction vibration damper at the front. In line with Alvis practice of the day, the familiar all-synchromesh gearbox was mounted separately from the engine and drove the rear axle through an open propeller shaft. Various figures have been quoted for the power output, from “about 100” to 115 bhp, for this smooth and quiet unit. A radiator 4” or so taller than the Speed Twenty made for a more imposing body line and was graced by a grille with a large number of narrow vertical slats. Cooling arrangements had no thermostat or bypass, relying on the pump driven from the front of the dynamo. The combined magneto and coil ignition system was carried forward from the earlier models. Carburation was by three substantial S.U. instruments with twin air silencers and a starting carburetter. Lucas P100 headlamps were fitted, along with smaller pass lights, whilst the spare wheel migrated to the rear.  Maximum speed was 91 mph and from 0 – 50 mph took 12 seconds.

The 3½ Litre was clearly intended to compete directly with the established Bentley of similar capacity and by not offering standard bodies, the company was able to direct customers to the better bespoke coachbuilders of the day. Van den Plas, Mayfair Carriage Co., Freestone & Webb, Gurney Nutting , Lancefield, Arthur Mulliner, William Arnold, Mann Egerton and Bertelli all bodied 3½ Litre chassis, along with Alvis regular Charlesworth. Most were saloons but drophead coupés and tourers also appeared, plus at least two sedanças de ville. One car was bodied by Martin & King in Australia. Prices ranged from £775 for the chassis through £1,170 for a saloon with the pillarless Freestone & Webb example coming in at £1,270. The 3½ Litre represents a period when increasing sophistication and weight of both coachwork and chassis necessitated increasing engine size and power to cope.

Deliveries commenced in July 1935 and were complete by late August 1936, except for one car in December.  Late in 1936 the Speed 25 and 4.3 Litre models supplanted the Speed Twenty and 3½ Litre respectively. Essentially the Speed 25 used the 3½ litre engine in a 10’4” chassis with standardised series-built bodies whilst the 4.3 Litre was aimed at the carriage trade with the longer chassis and a bored-out version of the engine. The 3½ Litre was a short-lived Alvis model, but a significant one.