Bentley 3 Litre

Infobox Automobile
name=Bentley 3 Litre


manufacturer=Bentley
production=1921–1929
1622 producedcite book |last=Baldwin |first=N. |title=A-Z of Cars of the 1920s|year=1994 |publisher=Bay View Books |location=Devon, UK |id=ISBN 1-870979-53-2]
class=Sports car
successor=4½ Litre
engine=3.0 L OHC 4-valve I4
designer=Walter Owen Bentley
wheelbase=Auto in|108|0
Auto in|117.5|0
Auto in|130|0The 3 Litre was the sports car that put Bentley on the automotive map. It was a large car compared to the tiny, lightweight Bugattis then dominating racing, but its innovative technology and strength made up for its weight. The 4000 lb (1800 kg) car won the 24 Hours of Le Mans in 1924, with drivers John Duff and Frank Clement, and again in 1927, this time in Super Sports form, with drivers S. C. H. "Sammy" Davis and Dudley Benjafield. Its weight, size, and speed prompted Ettore Bugatti to call it "the fastest lorry in the world."

Coachwork

The 3 Litre was delivered as a running chassis, with Bentley referring many customers to Vanden Plas for standard bodies. Most were open touring cars, but some variety was inevitable with custom coachwork. Customers included Prince George, Duke of Kent, Gertrude Lawrence, and Beatrice Lilliewere.

Engineering

The 3.0 L (2996 cc/182 in³) straight-4 engine was large for its day, but it was its technical innovations that were most noticed. It was one of the first production engines with 4 valves per cylinder, and these were driven by an overhead camshaft. It was also among the first with two spark plugs per cylinder, pent-roof combustion chambers, and twin carburetors. It was extremely undersquare, optimized for low-end torque, with a bore of 80 mm (3.1 in) and a stroke of 149 mm (5.9 in). To increase durability, the iron engine block and cylinder head were cast as a single unit.

Power output was roughly 70 hp (52 kW), allowing the 3 Litre to hit 80 mph (129 km/h). The Speed Model could reach 90 mph (145 km/h), while the Super Sports passed 100 mph (161 km/h).

A four speed gearbox was fitted.

On the early cars the brakes only operated on the rear wheels but from 1924 four wheel brakes were used.

Variants

There were three main variants of the 3 litre and they became known by the colours commonly used on the radiator badge. There is, however, no definitive rule controlling badge colours and the factory would supply any colour requested.

Blue label

This was the standard model with Auto in|117.5|0 wheelbase from 1921 to 1929 or long Auto in|130.0|0 wheelbase from 1923 to 1929.cite book |last=Georgano |first=N. |title=Beaulieu Encyclopedia of the Automobile |year=2000 |publisher=HMSO |location=London |id=ISBN 1-57958-293-1]

Red label

This used a 5.3:1 high compression engine in the Auto in|117.5|0 wheelbase chassis and was made from 1924 to 1929.

Green label

Made between 1924 and 1929 this was the high performance model with 6.3:1 compression ratio and short Auto in|108|0 wheelbase chassis. 100 mph performance was guaranteed.

Production

The 3 Litre car was shown at the 1919 London Motor Show, but the engine had not yet been finished. It took two years to get the engine right, with the first customer delivery in September 1921. Production lasted through 1929, by which time the car had been surpassed by Bentley's own 4½ Litre car.

* Experimental: 3
* 3 Litre: 1088
* Speed Model: 513
* Super Sports: 18

References