A Rough Guide to Bentley Identification

Broadly speaking, Bentley motor cars fall into three categories, according to when they were made and by what company: "W O"s made by W O Bentley at Cricklewood, "Derby Bentleys" made by Rolls Royce in Derby and "Crewe Cars" made post World War II by Rolls Royce at Crewe. Crewe Cars are subdivided into chassis-based and monococque and the latter, somewhat arbitrarily, depending who you talk to. Then there are the Specials, which usually have parts from different eras.

CategoryPeriodMade byAlso known asTypes
Vintage Bentleys1919-1931W O BentleyWO cars; Cricklewood Bentleys3, 4½, 6½, 8 and 4 litre
Derby Bentleys1931-1939Rolls RoyceRolls Bentleys* (non-U)3½, 4¼ and Mk V
Post-war1946-1965Rolls RoyceCrewe cars (chassis-based)Mk VI, R type, S types
Modern1965-1998Rolls RoyceModerns; Crewe cars (monococque)T types, Mulsanne, Turbo R, Continental R, Azure
1998-dateBentley MotorsModerns; Crewe cars (VW era)Arnage, Continental GT/GTC/Flying Spur, Brooklands, Azure, Mulsanne, New Flying Spur

* An infelicitous term, best not used in the company of Bentley afficionados

Not everyone would agree with my sub-division of the post-war cars; some might further sub-divide the period at 1971 to reflect the formation of Rolls Royce (1971) Ltd, when Rolls Royce Motors was separated from the aeroplane business. By 1998, Rolls Royce Motors was owned by Vickers, who sold it to BMW, but sold the Bentley name and the Crewe factory to Volkswagen; that is the basis for my sub-division.

This is not intended as an historical account, but a rough guide to identifying Bentley motor cars that you may see on the road or at "classic car" events. Errors and omissions are mine alone. For a detailed historical account, the Bentley Motors website breaks the history down decade by decade. Another interesting site is K J Rossfeldt's rrab.com, which claims to have photographs of every model of Rolls Royce and Bentley ever built. I make no such attempt, but concentrate instead on details by which Bentley models may be distinguished one from another.

Vintage Bentleys

The Vintage Sports Car Club defines a "Vintage" motor car as one built before 1930. By this strict definition, the last of the "W O" or "Cricklewood" Bentleys do not qualify, but few people make this technical distinction in respect of Bentleys made at Cricklewood.

There are five models, two with four-cylinder engines and three with six-cylinders, though the last of the six-cylinder engines (the 4 litre) was not a W O Bentley design. Bentley's engines were designed for power and reliability, with non-detachable cylinder heads and four valves per cylinder, operated by a single overhead camshaft.

Four-cylinder cars - 3 and 4½ litre

The first Bentley was the 3-litre. Most surviving 3 litre cars now carry open bodywork. In most cases, these are not the bodies supplied to the first owners. The Bentley factory did not do coachwork, but sent the rolling chassis to a coachbuilder of the customer's choice. Before long, W O decided that his cars needed more power, so he increased the engine size to 4½ litres. [The 6½ was already in production, but was more expensive; the 4-cylinder cars aimed at a different market.] There are few external clues to differentiate between 3 litre and 4½ litre cars if seen apart: if seen together, the 4½ appears significantly larger than the 3 litre. In fact, all the Cricklewood cars were of the same width, though chassis lengths varied considerably, 4½s' being longer than 3 litres'.

Seen individually, the most obvious difference is that the radiator of the 4½ litre is both wider and taller, to dissipate the additional heat from the larger engine. The curvature at the top is also subtly different, as shown in the following photographs.
The extra height gives the 4½ litre cars a larger "presence" than a 3 litre.

Left: the Bentley 3 litre radiator is straight-bottomed, with starting handle below.

Right: the Bentley 4½ litre radiator extends down on either side of the starting handle guide, which sits in an inverted "U".

Unfortunately for the Bentley-spotter, this is only a guide, since a good many 3 litre cars have been fitted subsequently with 4½ litre engines, but seldom with 4½ litre radiators. Such cars are known as "3/4½"s. The majority of surviving 4-cylinder Bentleys have been considerably modified during the 80-years since the Cricklewood factory closed, so the only way to be sure of what you are looking at is to know the car's history or to see it with its bonnet open on the exhaust side. The exhaust manifolds are different: the 3 litre's is attached by four bolts to its downpipe, whilst the 4½'s has eight.

Seen together, there are distinct differences between the 4½ (left) and 3 litre (right). In fact, the latter is a 3/4½.
The difference in shape at the top of the radiator (where the shell meets the core) is plain in this photograph.

3 litre "100 MPH" model

The tapered radiator on this 3 litre Bentley identifies it as one of the fourteen "100 MPH" cars.

4½ litre "Blower" Bentleys

A small number of 4½ litre cars were supercharged. These are known as "Blower" Bentleys and are clearly distinguished by the presence of a finned supercharger at the base of the radiator. W O Bentley did not approve of this, his philosophy being that the way to get more power was to increase engine size; supercharging, in his view, made his cars unreliable. This photograph is of a Petersen re-creation, to illustrate the appearance of the supercharger: note the SU carburettors.
When I find an original "blower" Bentley to photograph, I'll add an image to this page.

Here are some images of an 1929 "Blower" Bentley.

Six-cylinder cars - 6½, 8 litre and 4 litre

In keeping with his philosophy that there is no substitute for litres, W O designed a 6½ litre, six-cylinder engine, to provide more power, both for his racing cars and for customers who wanted large, heavy coachwork for their motor cars, but still expected good performance.

Except for the 4 litre, the six-cylinder Vintage Bentleys can be distinguished by the presence of a dynamo casing (quite different from the supercharger of a "Blower") at the base of the radiator. (Confusingly, some very early cars had dynamos driven from the rear of the engine, though whether any of these survive unmodified I do not know.)

The car on the left is a "Standard Six" with its original Sedanca de Ville coachwork by H J Mulliner and the tapered radiator shell characteristic of the Standard Six. Its dynamo casing is paint-finished. On the right is a "Speed Six": its dynamo casing is unpainted and has been polished. The parallel-sided radiator is characteristic of the Speed Six, which was fitted with twin SU carburettors to increase the performance over the Standard Six, which had a single carburettor and complicated inlet manifold. (Again, confusingly, this particular car now carries triple SUs.)

1930 Speed Six with saloon coachwork by Gurney Nutting

These two photographs of another Standard 6½ clearly show the inlet attangements and tapered radiator shell. Note also that the inlet is on the left side of the engine and, ergo, the exhaust must be on the right. The 6½ is the only Bentley engine with this conformation, so a right-hand exhaust is another clue to its identity compared with the 8 litre. The reason for this seems to be that there was difficulty in finding room for the throttle linkage on the same side as the steering column; the difficulty was evidently overcome when the 8 litre was designed.

The 8 litre is distinguished by a vaned radiator shell. This one has a paint-finished dynamo casing and wheel discs. The radiator vanes were thermostatically-controlled to aid fast warming of the engine from cold and to maintain a constant temperature thereafter.

The 4 litre

Many - perhaps most - vintage Bentley enthusiasts regard the 4 litre Bentley as an aberration. Certainly, W O did. It was produced in a somewhat desperate attempt to generate cash-flow for the company to keep it afloat when the market for expensive luxury cars was poor. The attempt failed, and the Bentley company was acquired by Rolls Royce in 1931. The 4 litre pushrod engine - anathema to W O - was mounted in chassis designed for the 8 litre engine, the result being an under-powered motor car, not at all in the spirit of W O Bentley. This error was compounded when heavy coachwork was mounted. Few 4 litre cars were sold.

The massive 8 litre chassis allowed coachbuilders to mount heavy bodies, similar in style and accoutrements to the 8 litre cars, as this photograph of a 4 litre car shows.

The absence of a dynamo beneath the radiator distinguishes this from an 8 litre Bentley. The wheel nuts (spinners) clearly identify this as a Cricklewood car. Derby-built cars were quite different.

Next: Derby Bentleys

March 2014, updated July 2015