1931 Bentley 8-Litre Restoration to Original Specs

The Bentley 8-Litre, introduced in 1930, was W.O. Bentley's final and most ambitious creation. The 8-Litre was designed as a refined yet immensely powerful luxury car, capable of effortlessly reaching high speeds. The massive six-cylinder engine delivered exceptional torque, allowing the car, regardless of body style, to reach speeds of over 100 mph (160 km/h), a remarkable achievement for its time. W.O. Bentley considered the car his masterpiece, combining technical refinement with exceptional smoothness and quietness. The model was aimed squarely at the top end of the luxury market, competing with the finest models from Rolls-Royce, Hispano-Suiza, and Isotta-Fraschini. Coachbuilders such as Mulliner, Gurney Nutting, and Vanden Plas created bespoke bodies that emphasized the chassis' elegance and versatility. Despite its excellence, the 8-Litre arrived at the worst possible time, when the global economic crisis severely impacted demand for ultra-luxury cars. Only one hundred examples were built before Bentley Motors went bankrupt in 1931. Rolls-Royce acquired the company shortly thereafter and immediately halted production of the 8-Litre, as it was considered a direct competitor to the Phantom II. The surviving cars are prized for their rarity, technical perfection, and the clear way in which they embodied W.O. Bentley's design philosophy. Today, the 8-Litre is considered one of the most prized British pre-war cars, renowned for its combination of performance, craftsmanship, and impressive presence.

Technical data

Engine: Six cylinder inline engine with single overhead camshaft (OHC)
Cylinder capacity: 7,983 cc (8.0 litres)
Induction: Twin S.U. carburettors and Autovac fuel‑lift system
Petrol tank: 25 gallons standard - 30 gallons long range (95-115 liter)
Ignition: Twin‑spark system using both magneto and coil ignition
Capacity: Approx. 220 bhp at 3,300 rpm
Torque: Never given but well over 400 Nm
Top speed: Approximately 100 mph, depending on bodywork and gearing.
Gearbox: Four‑speed manual
Clutch: Single dry‑plate clutch.
Brakes: Mechanical four‑wheel drum brakes with servo assistance
Suspension: Semi‑elliptic leaf springs front and rear with friction dampers
Drive: Rear‑wheel drive
Wheels: Wire wheels with Rudge‑Whitworth centre‑lock hubs (varied by coachbuilder)
Bodywork: Coachbuilt to order by Mulliner, Gurney Nutting, Vanden Plas, Harrison, Corsica, Murphy and others
Weight: Approximately 2.5 tonnes, depending on coachwork.

Bentley history 1919 - 1931

The famous Bentley make, erected by Mr. W.O. Bentley, existed as a independent firm for only twelve years (1919-1931) before the proud firm was taken over by the Rolls Royce motor company. Those twelve exhilarating Bentley years were filled with racing successes and many important victories. The Bentley name as manufacturer of large, heavy, powerful and rugged sports cars has been imprinted in the human mind since the "roaring" 1920ies.

Bentley motorcars won the famous 24 hours of Le Mans race in the years 1924, 1927, 1928, 1929 and 1930. The years they did not win the long distance reliability race for production cars they finished second or third. Not only successes at Le Mans were counted but also victories in other long distance events like the Brooklands 500 mile race. The racing successes were mainly due to the rugged built of the cars and the meticulous preparation of the cars. In every race they learned and had the cars improved on small but important details (Head lamp covers, mesh gauze on the petrol tank, quick filler caps for engine oil and radiator, driver adjustable brakes.)

3-Litre

The Bentley 3 Litre was W.O. Bentley’s first design. The car was presented in 1919 but the first cars were sold in 1921. The four cylinder cars of rugged construction where in a class of their own for they combined the size and comfort of the big tourers and saloons with the road holding, and speed of the smaller sports- and racing cars. The Bentley was a true owner-driver car for the sporting motorist and connoisseur. The Bentley car could be had in three different types which were designated with three different radiator badges*. Red badge: short chassis speed model, Blue badge: the early short and then long chassis type for bespoke bodywork, Green badge: very rare and used for about eighteen 100 mph. These Green badge car won at Le Mans in 1924 and 1927 (Old Number Seven.) The 3-Litre was built from 1919 until 1929.

*The Bentley radiator and the logo were designed by the genius motoring artist Gordon Crosby. The logo is a ‘badge’ and not a ‘label’ as stated by AFC Hilstead in his book ‘Those Bentley Days’ (published 1953).

6.5 Litre and Speed Six

Then in 1926 the 6.5 Litre and the Speed Six were presented, these six cylinder models were in the eyes of W.O. Bentley the best cars the Bentley firm ever built. The bigger capacity was needed for many a customer had built a bespoke heavy saloon body on their chassis and thus eliminating the sporting element the chassis had to offer. The Speed Six brought Bentley the most racing successes and Le Mans victories. In the year 1929 the Speed Six came home first with Bentley 4.5 Litres second, third and fourth! In 1930 the same Bentley Speed Six 'Old Number one' came home a victor followed by another Speed six in second position!

4.5 Litre

Next came the upgraded four cylinder Bentley 4.5 Litre in the year 1927. The 4.5 Litre featured four valves per cylinder and two spark plugs per cylinder engine. Most of these cars were given open tourer and saloon bodywork and only nine short chassis were built.

4.5 Litre Supercharged (Blower)

The 4.5 Litre Blower was built in the ‘Barnato’ period. Financed by the Hon. Dorothy Paget Tim Birkin successfully experimented at Brooklands with his blower Bentley and even achieved the Brooklands lap record with his Blower Bentley. As Woolf Barnato was now in charge of the Bentley firm, and W.O. now only responsible for the development of the Bentley cars, Birkin convinced Barnato to enter a separate team of Blower Bentleys for the 1930 Le Mans race. This was against W.O. Bentley’s ideas for he was of the opinion that the supercharger would only add trouble to a perfectly good and reliable machine. The 1930 Le Mans race proved W.O. right as none of the blown cars finished and Barnato and Kidston won on a Speed Six model.
The supercharged 4.5 Litre engines were real "gas-guzzlers", the naturally aspirated 4.5 Litre engine used one litre of petrol every 5.6 kilometres, the supercharged engine used one litre for just 3.5 kilometres, a very large petrol tank was fitted additionally.
Another problem was that spark plugs in the supercharged engine wore out very quickly resulting in loss of power. Bentley engineer Nobby Clarke stated one day: "The blower eats spark plugs like a donkey eats hay". Only 55 Bentley 4.5 Litre ‘blower’ cars have been built by the firm of which 26 carried the Van den Plas open tourer bodywork.

8-litre

In 1931 the most impressive Bentley model ever saw the light of day; the 8-Litre. This car can be regarded as a real ‘super car’. Only 100 of these big cars have been built.

4- Litre

Also in 1931 a down scaled 8-Litre was introduced, the 4-Litre. The car was designed to sell more cars to improve the cumbersome financial situation at Bentley’s. The 1929 Wall Street crash affecting the firm immensely. The 4-Litre featured the chassis, transmission and brakes of the 8-litre. The newly constructed 120 bhp ‘Ricardo’ engine proved underpowered for the chassis and as a result the 4-litre never became the success Bentley hoped for. Only 50 chassis were built.

1931 Rolls Royce take over

In 1931 business prospects looked very black and the firm went into receivership. Napier & Son were negotiating with Bentley's receiver to take over the company. Then another interested party arrived at the scene named British Central Equitable Trust. They outbid Napiers in a sealed bid auction. The Trust later was found to be a front for Rolls-Royce Limited. Rolls Royce had cleverly defeated the threat of a firm that could become a very unwelcome competitor.

From 1933 all Bentley cars were based upon their Rolls Royce counterparts and production was then moved from Cricklewood to Derby. Purists tend to name the Rolls Royce produced cars – Rolls Royce Bentley’s. Rolls Royce took good care of the Bentley ‘marque’. Many magnificent automobiles were built with a distinctively different character than the Rolls Royce models.

_{© Marc Vorgers}