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1930 Bentley 4.5 Liter Supercharged

Walter Owen (W.O.) Bentley was the youngest of nine children and the son of a prosperous family that could afford to have him privately educated at Clifton College in Bristol. At the age of 16, he began a premium five-year apprenticeship working as an engineer with the Great Northern Railway at Doncaster in Yorkshire. This gave him practical experience with complex railway machinery including the casting and manufacturing of many components. When his apprenticeship ended in the summer of 1910, he decided to forsake the railroad and seek employment elsewhere.

Joined by his brother, H. M. (Horace Millner), the duo formed a company in 1912 called 'Bentley and Bentley' with the purpose of selling French DFP cars. Unimpressed with the DFPs performance, W.O. added lightweight aluminum alloy pistons and a modified camshaft, resulting in a car that captured several records at Brooklands in 1913 and 1914.

With the onset of World War I, W.O. applied the use of aluminum alloy pistons to military applications, increasing the output of the engines, as well as allowing higher compression ratios and engine speeds, while operating at cooler temperatures. His contributions earned him the MBE award (Most Excellent Order of the British Empire).

Bentley Motors
On Stand 126 at the 1919 Olympia Motor Exhibition, W.O. Bentley debuted a new 3-liter car equipped with a prototype engine that had fired up for the first time just a few weeks earlier. Bentley Motors Limited was founded in humble premises located in New Street Mews, Baker Street, London. W.O. was joined by Frank Burgess (formerly of Humber) and Harry Varley (formerly of Vauxhall Motors), along with engineer Clive Gallop. The first complete Bentley 3 Litre car was road tested in January of 1920 and the first production version was delivered in September of 1921. The 3 Litre model would form the foundation for the company's prestigious legacy in motor racing competition. Its iconic radiator, leather-strapped bonnet, and British Racing Green livery would become the archetypal vintage sports car.

Among the early motorsport accolades were a second, fourth and fifth place finish at the 1922 Isle of Man Tourist Trophy, earning Bentley the Team Prize. This accomplishment birthed the TT Replica, which later became known as the Speed Model. The Bentleys competed in hill climbs and at Brooklands, and a single 3 Litre raced at the Indianapolis 500 mile race in 1922 driven by Douglas Hawkes to a thirteenth place finish. Jean Chassagne won the 1921 Grand Prix Sunbeam, and he would later become part of the famed 'Bentley Boys,' a group that would include Woolf Barnato, Jack Dunfee, Tim Birkin and Sammy Davis. The team's inaugural outing at Le Mans was in 1923 when Duff and Frank Clement's private entry took fourth place. The following year, a 3 Litre won Le Mans and subsequent models won again in 1927, 1928, 1929, and 1930.

Production of the 3-Liter Bentley lasted from 1921 through 1929 with 1,622 examples built.

The Bentley 4½ Litre
As the competitiveness of the 3 Litre began to diminish, coupled with the heavy and voluptuous coachwork being applied to many road-going chassis, Bentley introduced the 4½ Litre model.

1930 Bentley 4.5 Liter Supercharged photo
LeMans Sports by Vanden Plas
Chassis #: 3918
View info and history
Before the four-cylinder, 4½ Litre model, Bentley had created the 6½ Litre model. A prototype was created in 1925 with an experimental six-cylinder engine of 4½ litre capacity. A rumor exists that states that while the car was being tested in France, its driver encountered Rolls-Royce's 'New Phantom' undergoing similar trials. Naturally, something of a race is said to have ensued, the outcome of which immediately led Bentley to increase the capacity of its embryonic engine to no less than 6½ litres. Produced from 1926 to 1930, the 6½ Litre model later spawned the immortal Speed Six, which is said to have been W.O.'s favorite among all the illustrious motorcars he created.

The 6½ Litre model was expensive, with a larger chassis than the 3 Litre, a more potent engine, and was suitable for the large, heaving limousine bodies that many customers preferred.

The new 4½ liter model was in essence two-thirds of the six-cylinder 6½-liter unit. It effectively employed the chassis, transmission and brakes of the 3 liter, with its four-cylinder motor retaining the six's 100x140mm bore/stroke plus the company's familiar four-valves-per-cylinder fixed-head architecture, but with the front-end vertical camshaft drive of the 3-liter. Most engines used two valves per cylinder, but the Bentley engine had four valves per cylinder actuated by a single overhead camshaft. With two SU carburetors and dual ignition with Bosch magnetos, the road-going versions developed 110 horsepower while the uprated racing versions produced 130 bhp.

1930 Bentley 4.5 Liter Supercharged photo
LeMans Sports by Vanden Plas
Chassis #: 3918
View info and history
The chassis was formed from steel and reinforced with ties. The brakes were conventional with 17-inch drums operated by rod and finned for cooling. The four-speed gearbox was unsynchronized and the suspension was comprised of semi-elliptic leaf springs.

Production of the 4½-Litre lasted for four years, and all but ten of the 667 cars were built on the 3-Litre's 'Long Standard', 10-foot 10-inch-wheelbase chassis. The length measured 172.4 inches and the width of 68.5-inches. The shorter platform had a wheelbase of 117.5-inches. Like other Bentley models of the period, buyers were able to specify their preferences from a range of mechanical and electrical equipment, in addition to their preferred coachbuilder and body style. In racing guise, a properly prepared 4½-Litre was capable of 120 mph.

The first Bentley Team car to race with the 4.5-liter engine was 'Old Mother Gun,' essentially a three-liter team car fitted with a new cylinder block. During the 1927 Le Man's race, the new 4.5-liter engine proved fast until the historic Maison Blanche crash. The infamous White House crash involved eight cars including all three of the Bentley team entries and caused the retirement of two of them. The third Bentley, albeit badly damaged, managed to win the race. It was a 3 Litre Speed model driven by Dudley Benjafield and Sammy Davis. Later that same month, Old Mother Gun was run at the Grand Prix de Paris, which it easily won. This was the first victory for the new 4 1/2-litre engine.

1930 Bentley 4.5 Liter Supercharged photo
LeMans Sports by Vanden Plas
Chassis #: 3918
View info and history
For the 1928 racing season, Bentley worked on preparing new works cars based on the 4 1/2-litre production chassis in addition to Old Mother Gun. The first two examples built were YV 7263 and YW 2557, and wore lightweight Le Mans coachwork created by Vanden Plas. The specialized production chassis consisted of an ash frame with fabric covering, complete with a rear D-shaped fuel tank mounted with a vertical spare. Covered with a rounded aluminum shroud, the resultant appearance earned the cars their 'Bobtail nickname.

During the 1928 24 Hours of Le Man's race, YW 2557 suffered a broken frame and Old Mother Gun suffered a similar fate, breaking its frame shy of the finish, yet Barnato was able to limp it to victory. The car driven by Birkin finished 5th overall. On the return trip from Le Mans, the third 4 1/2 Litre broke its frame. Upon return to Cricklewood, each of the team cars received new frames with significant chassis strengthening.

The 4½ liter Blower Bentley
The 4.5 litre Blower Bentley originated from the vision of Sir Henry Birkin, whose goal was to increase the performance of the 4½ Litre model and to convince then-company Chairman Woolf Barnato of its potential. Barnato seemingly agreed, despite W.O. Bentley's early objection to the supercharged concept.

1930 Bentley 4.5 Liter Supercharged photo
LeMans Sports by Vanden Plas
Chassis #: 3918
View info and history
The concept was simple; attach a Roots-type supercharger to the 4.5-liter engine. The work was performed by engineer Amherst Villiers, who had also produced the supercharger. Since W.O. refused to allow the engine to be modified to accommodate the supercharger, the unit was placed at the end of the crankshaft, in front of the radiator. Employing a unique lubrication system, along with special pistons and crankshaft, the engine produced 175 bhp at 3,500 for the touring model and 240 hp at 4,200 rpm in racing guise.

To comply with the homologation restrictions of Le Mans, the factory was required to build fifty examples. The inaugural competitive outing for the 'Blower' Bentley was in June of 1929; July brought the first podium finish. Satisfied with its potential, production of the supercharged cars began that June with the intent of displaying two production 'Blowers' on the stand at the 1929 Olympia Motor Show. Customers began receiving the production Blowers by 1930. The first 25 supercharged cars received chassis numbers beginning with SM; these had smooth-cased 'blowers.' The subsequent 25 chassis numbers, beginning with MS, had ribbed blowers to aid cooling.

Having satisfied the Automobile Club de l'Ouest requirements to compete at Le Mans, the Blower Bentley were able to 'toe' the line in 1930. While powerful, the Blower Bentleys were less reliable than its naturally aspirated siblings. The two Blower models entered in the 1930 24 Hours of Le Mans by Dorothy Paget, one of which was co-driven by Tim Birkin, did not complete the race. Birkin placed second in the French Grand Prix at the Circuit de Pau in 1930.

1930 Bentley 4.5 Liter Supercharged photo
LeMans Sports by Vanden Plas
Chassis #: 3918
View info and history

When the Blower Bentley was able to finish the race, the result was often monumental. Mildred Bruce, a British female racer, achieved a 24-hour distance record at Montlhéry in a Blower Bentley, with an average speed of 89.5 mph.

Production
Production of the 4½ Litre Bentley ended in November of 1931 with 720 examples built, including 50 supercharged examples.


by Daniel Vaughan | Nov 2022

Related Reading : Bentley 4½ Litre Blower History

The Bentley 4 12 liter came into existence to fill a void left by the 3-liter and the 6.5-liter variants. The 3-liter suffered from underperformance while the 6.5-liter was unsafe for the roads. The 6.5-liter was powerful, and with poor road-conditions often caused tires to fail quickly. The solution was the Bentley 4.5-liter a vehicle that had enough power to carry the vehicle down the road at....
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1930 Bentley 4.5 Liter Supercharged Vehicle Profiles

1930 Bentley 4.5 Liter Supercharged vehicle information
Drophead Coupe

Coachwork: Gurney Nutting
Chassis #: SM3909
Engine #: SM3910
1930 Bentley 4.5 Liter Supercharged vehicle information
Open Sports Tourer

Coachwork: Vanden Plas
Chassis #: SM3913
Engine #: SM3916
1930 Bentley 4.5 Liter Supercharged vehicle information
LeMans Sports

Coachwork: Vanden Plas
Chassis #: 3918

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Performance and Specification Comparison

4½ Litre Blower

Specification Comparison by Year

Year
Production
Wheelbase
Engine
Prices
130.00 in.
4 cyl., 274.61 CID., 182.00hp

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