1929 Bentley 3-Litre

Walter Owen Bentley was a railway engineering apprentice turned aero-engine designer, before creating a firm that bore his name, and produced its 3 Litre automobile from 1919 through 1929. It was first made available to customer's coachbuilders beginning in 1921 with most receiving coachwork from Bentley's near neighbor Vanden Plas. Virtually all of the Le Mans campaigns by the 3 Litre Bentleys wore lightweight open four-seater touring bodywork by Vanden Plas. even after the four-cylinder cars were usurped by its 6-cylinder siblings, the most sporting examples often wore this guise. A 3 Litre chassis had been on display on Stand 126 at the 1919 London Motor Show (Olympia Motor Exhibition), the engine having fired up for the first time just a few weeks earlier.

The three-liter straight four-cylinder engine was designed by ex-Royal Flying Corps engineer Clive Gallop, and was one of the earliest production cars to use four-valves per cylinder, an overhead camshaft, and dry-sump lubrication. It used a bevel-geared shaft drive for the camshaft that was based on the 1914 Mercedes Daimler M93654 racing engine and was among the first to use two spark plugs per cylinder, twin carburetors, and pent-roof combustion chambers. The long-stroke undersquare engine had an 80mm bore and a 149 mm stroke, optimized for low-end torque. Twin ML magnetos provided the ignition and power was transmitted via a four-speed gearbox with right-hand change. Rear-wheel brakes provided the stopping power up to 1924 when four-wheel Perrot-type brakes were introduced.

The standard model was known as the 'Blue Label' and rested on a pressed-steel 117.5-inch wheelbase chassis (1921 to 1929) or longer 130-inch wheelbase (1923 to 1929).
The initial offerings by Bentley were among the most expensive cars on the market, a bold stance considering the company's inexperience and lack of reputation. The mechanical prowess and attractive coachwork were soon joined by the marque's first victory, achieved at Brooklands during the May 16th, 1921 Whitsun meeting. International recognition soon followed, with a purpose-built racer, Douglas Hawkes'streamlined but otherwise comparatively standard Bentley, finished the 1922 Indianapolis 500 in 13th place overall with an average speed of 74.95 mph. Just a few weeks later, the Cricklewood firm fielded a team of three Works cars for the Isle of Man Tourist Trophy race. Driven by Frank Clement, W.O. Bentley and Douglas Hawkes, the trio took the chequered flag in second, fourth and fifth places respectively. W.O. missed out on third place by a mere six seconds. Interviewed after the event he commented: 'Our primary motive was to put the cars in the public eye and get them talked about . . . and the results were very pleasing'.

Following the success at the Tourist Trophy, where the team had taken the Team Prize, Bentley introduced the 3-Litre TT Replica (later known as the Speed Model). They used the existing 9 foot, 9.5-inch wheelbase, short standard chassis, and were identified by the Red Label on its radiator. The Speed Model differed by having a higher compression ratio, different camshaft, twin SU 'sloper' carburetors, and the close-ratio A-Type gearbox (the latter being standard equipment prior to 1927 when the C-Type gearbox was adopted). With these modifications in place, horsepower rose from the standard 70 to 80 bhp and top speed increased to 90 mph. Other enhancements included the larger, 11-gallon fuel tank and often the addition of Andre Hartford shock absorbers.

The inaugural Le Mans 24-Hour race was held on May 26th and 27th of 1923, and although skeptical about the new event, W.O. made the last-minute decision to attend. Duff and co-driver Frank Clement overcame a holed fuel tank to claim fourth place overall, establishing the fastest lap in the process. A year later, Bentley recorded its first Le Mans victory with its 'Speed Model.'

Along with the Blue and Red Label specification, Bentley also had the Green Label (1924 to 1929), which had a 6.3:1 compression ratio engine installed in a short 108-inch wheelbase.

Near the close of 1926, the factory created the first supercharged Bentley - chassis number 220 FR5189. It used a Roots-type blower attached to the 3-liter engine and pre-dated the Birkin supercharged Bentleys by two years. The blower was mounted in front of the radiator, between the dumb irons, and driven by the crankshaft.

The production total of the 3-Litre Bentley reached 1,613 chassis with a third of those being the short chassis Speed models.

by Daniel Vaughan | Sep 2020