The History of the SU Carburetter

The SU carburetter was the brainchild of the late George Herbert Skinner. He was born at Ealing in April 1872, the son of William Banks Skinner, a director of the well-known Lilly & Skinner footwear distributors. Despite following his father into the footwear business, Herbert's real passion lay with the motorcar.

Herbert was educated at Castlebar School in Ealing, and although as far as is known he had no technical training, by 1900 he had submitted three provisional patents covering his ideas. In 1903 he is reported to have travelled to France to learn how to drive a car. The following year he and his younger brother Thomas Carlisle Skinner decided to put some of his ideas into practice and improve the carburation on a Star motor-car they owned at this time. The vehicle's massive old carburetter was fitted with a glass top through which they could watch the flow of fuel from the jet. It was clear that the suction (depression) on the jet varied in accordance with the demands made by the engine, and it seemed to them that a big improvement would be made if the jet could be located in an air channel of a size varied to suit different engine speeds, so ensuring a constant depression and air velocity.

A crude mechanism was evolved to bring this about, but it was then found that it lacked overall performance because if a jet orifice was chosen that was suitable for full throttle running, then this would result in an over-rich mixture for slow running and vice versa. The answer to this problem was a tapered needle; this varied the size of the jet orifice according to engine demands. A full patent was applied for by Herbert in February 1905 and granted in January 1906. Herbert's application describes his occupation as "Boot and Shoe Manufacturer".

If Herbert was the inventive genius, his brother Carl was the practical 'engineer'. Carl was born at Ealing in June 1882 and educated at the Leys School in Cambridge. Again it is not known where or even if he received any technical training. Carl also joined the family business but by 1906 he had teamed up with R.P.Wailes to manufacture and fit carburetters. There was also a third brother by the name of John, of whose involvement little is known other than that he appears to have been a director of the Company by about 1913.

It is not clear when the first experimental carbs were produced, but they were almost certainly made at George Wailes & Co.'s works at 258 Euston Road. When George Wailes sold the works and premises in 1906, Carl became a partner with George's son and they took temporary premises in Euston Buildings while new works at 386-388 Euston Road were being built. For some years carburettors were fitted and tuned to individual cars. The new works had an 8ft by 16ft, 30cwt capacity lift which served all four floors as well as the roof and basement. Surprisingly, the top floor was used to fit and tune while the carburettors themselves were manufactured in the works below from working drawings prepared by the Chief Draughtsman, Mr J.O. Gardner, to Herbert's sketches.

Herbert's main responsibility appears to have been one of design and improvement, which he pursued with vigour and also protection by way of patents of his ideas; a full patent covering the 'constant depression' idea was granted in England in 1906, and additional patents were taken out in Belgium, France, Germany, Italy and the USA. Herbert's inventive genius was not confined to the SU; he took out patents in 1907 and 1908 on a hydraulic variable speed gear and a detachable strap for ladies' court shoes and slippers, and later for a paraffin carburetter, an aero-carburetter and a supplementary fuel supply valve for cold starting. There is some evidence to suggest that the carburetter was originally branded "The Union Carburetter" but this was soon superseded by "The SU Carburetter", being the abbreviation of "Skinner's Union".

In 1910 the company moved to premises at 154 Prince of Wales Road, Kentish Town, North London, an old horse stable, the structure of which had to be converted to allow production to take place, and a Limited Company was registered in the name of The SU Company Ltd on the 2nd of August 1910: Reg. No 111416. The earliest financial information appears in the Company's ledger dated April 30th 1911. It is not specific as to who the directors were at this time, but an entry in the accounts of 28th January 1913 shows director's fees of £25 each to W.B. Skinner, G.H. Skinner and J.H.Skinner. By this time the accounts also show that Wolesley and Rover were regular customers of SU.

These early carburetters were fitted with leather bellows in place of the now familiar dashpot, and they appeared to have worked quite well. To maintain the leather bellows' suppleness a regular application of glycerine was recommended. The bellows themselves were made from glace kid by Herbert's wife Mabel at their home. Sales to the company from Mrs Skinner for bellows-making are recorded in the accounts right through to 1928; presumably by this time for spares, not production.

With the outbreak of war in 1914, carburetter production virtually ceased, the factory being busily occupied on Government contracts making machine-gun parts and tripods, bombs and aircraft carburetters. At this time there were about 250 employees. Carburetter production resumed after the war, but progress was slow. There was a general recession within the motor industry due to inefficiency and high costs, and the Company resorted to making wireless parts, windscreens, water cocks and other similar engineering work to remain in business. Some car manufacturers appreciated the qualities of the SU, however, and they were fitted to a number of quality cars such as Bentley, Napier and Invicta. During this time, the leather bellows were replaced by a brass piston (eg in the 1927 Sloper).

By the mid-twenties, after some initial problems, William Morris was fitting more and more SUs to his cars and in his usual style acquired the by now struggling company in December 1926. The takeover appears to have been somewhat acrimonious with the existing management probably left with the choice of selling out or going broke. The Company was immediately moved to the Midlands and installed in the works of another of Morris's new acquistions, the Wolesley factory at Adderley park, Birmingham. Carl came as part of the package, being made Managing Director.

This was the real turning-point for SU, and with all the cars in the Morris empire to service, SU production increased rapidly. According to Wilf Webster, who joined the company in 1929 as Assistant Draughtsman, money for expansion and development was no problem: "We could have more or less whatever we wanted," he said, and so new products now started to arrive thick and fast.

1929 saw the introduction of the HV type carburetter with bottom feed float chamber and also the Petrolift which was the very successful forerunner of the electric pump. The Petrolift replaced the gravity feed petrol tanks or vacuum tanks which were the norm for this period. In 1930 the HV was modified to take the top feed float chamber, followed by the OM and D type in 1931, the latter standing for "down-draught", a design which required a spring in the suction chamber to return the piston to the idle position. 1931 was also the year that Herbert, the inventive "genius", died, sadly never to see the heyday of his protégé. In 1932 the first aero carburetter was developed and from this beginning a number were produced for both military and civil aircraft during the mid- to late-1930's, including the Rolls Royce Merlin engine. The following year the L type petrol pump was introduced. This replaced the Petrolift and is still in production today in its original form.

The thirties were a time of almost frenetic development; SU would and did make almost anything for anybody requiring a fuel system and the growth in output in both production and designs was quite incredible. ln 1936 the name of the company changed to SU Carburetters Ltd. In 1937 the thermostatic automatic choke and the ubiquitous H Type was introduced - a series of carbs with choke bores ranging from 1 1/8th to 2 inches in 1/8th increments which were to be the standard right through to the end of the 1950s. In 1938 the hydraulic piston damper was introduced to provide acceleration enrichment. Various new pump designs had also appeared by now including the HP, LCS and double ended high capacity models. By 1939 nearly all Morris and MG vehicles as well as Riley, Woleseley, Alvis, Bentley, SS etc were equipped with either an SU pump or an SU carburetteror both, SU was thriving. In March 1939, according to a contemporary report, the SU factory covered 1,000 square feet and employed between 400 and 450 people making some 4,000 carburetters and 4,000 pumps a week plus quantities of aero-engine components. This year the zinc die-cast piston was replaced by brass, since zinc distorted or grew with age resulting in loose piston rods, and the HV type carburetter was phased out.

The second world war increased SU operations significantly - by the outbreak of hostilities the works employed some 700 people, an increase of 300 in about six months, supplying all the aero-carburetters for Rolls Royce Merlin, Vulture and Peregrine as well as Napier for their Sabre and Dagger engines. The company was also manufacturing its fuel pumps for many military applications. The dangers of this one factory supplying the entire aero-carburetter requirements of the RAF Spitfires, Hurricanes and bombers was realised in late 1939 and it was decided to set up a duplicate plant in the Riley works in Coventry.

Air raids in November 1940 caused damage to the works. In the first air raid the factory was set on fire, but this was contained and extinguished by the works's fire brigade, and although three high explosives scored direct hits, two in the machine shop, the carburetter production line plant survived intact. In the second raid no bombs fell on the SU works itself but girders and other debris from surrounding buildings came through the SU roof and the Ministry for Aircraft Production decided to evacuate the factory. After only twelve hours' notice the first of many RAF trucks arrived to remove the plant to a modern, newly-constructed factory at Highlands Road, Shirley, recently requisitioned from the Co-op. Production continued non-stop during the move, however, any gaps being filled by the Hiley shadow factory. After the move the number of workers quickly rose to 1,500. The weekly output of carburettors was doubled after Dunkirk to 200 a week, with a normal working day of 8am to 7pm. This working day was voluntarily stretched quite often with the workers sometimes sleeping on the floor next to their machines.

A second shadow factory was set up in the Wharf Valley in Yorkshire in 1941, in the village of Barwell, a boot factory requisitioned for the purpose. As well as the SU, this factory made the Rolls Royce Bendix Stromberg type carburetter. In 1942 the petrol injection pump was developed for the aero-engines, first fitted on Mosquito aircraft. Two SU technical staff had taken out a patent in 1939 but the firm could not get anyone interested in it at that time. After three years of neglect, the SU design was adopted and the new British petrol injection pump came into general use in the last year of the war. It was later built under licence by an American company and called The Simmonds Injector Pump.

In 1945 the production of carburetters and fuel pumps for motor vehicles was resumed and a move to the present site at Wood Lane, Erdington, Birmingham took place in July 1947. The "Skinner" connection was finally severed this year when Morris (Lord Nutfield) called a meeting with Carl, along with eight other directors from various parts of the Nuffield Empire, and announced that they were all sacked. A sad and somewhat ignominious end to a career dedicated to the development of his brother's ingenious invention. The following year saw the introduction of aluminium die castings replacing zinc and brass, a direct result of experience gained during the war years and making good use of the plentiful supplies of aluminium left over from aircraft production.

After the war, developments and new introductions came almost on a yearly basis. In 1950 dust proofing was introduced, in 1952 the formation of the British Motor Corporation widened the market for SU carburetters and pumps still further, and in 1954 were introduced both the part throttle weakener for single car applications on 6-cyl engines (eg Rover P4) and the HD type carburetter.

1958, the year Carl Skinner died, saw the introduction of the HS type carburetter, 1962 the delrin float needle, and the following year the nylon float needle on HS carburetters. 1967 saw the development and marketing of a mechanical fuel pump and shortly after an automatic enrichment device (AED). In 1969 the spring-loaded metering needle and throttle overrun valve were introduced, in 1971 jet temperature compensation on HSB carburetters, and in 1972 the HIF type. Jet temperature compensation was expanded to HS4 and HS6 carburetters in 1975; the following year the ball-bearing suction chamber was introduced and the part throttle weakener further developed.

By 1976 SU's position, that of a small plant in a rapidly declining car manufacturer known as British Leyland Motor Holdings, changed once again when it became part of a division of Service and Parts known as SU/Butec. With the demise of SU/Butec a few years later, SU lost its identity to become Austin Rover Fuel Systems, the beginning of a long period of drift and decline with SU parts becoming more and more difficult to service. By the early eighties SU was seriously considering ceasing production of HS pairs (for MGB Midget, Spitfire etc), but they were persuaded to keep tooling operational by Burlen Services.

Burlen Services, was formed in 1971, and first became involved with SU carburetters in the fuel crisis of 1974, when they were first appointed as agents. There followed a long period of co-operation, to the mutual benefit of both companies, culminating in a joint venture to rescue the defunct Solex UK production in 1985. Burlen now trades under the name of Burlen Fuel Systems which was formed in 1986.

In 1982 SU introduced the HIF44E carburetter, which had electronic control of the cold start function, idle speed and overrun fuel cut-off. In 1988 the Company was acquired by the Hobum Eaton Group, who themselves were acquired by the large USA based multinational Echlin Corporation eighteen months later. The Echlin Corporation granted SU true independence, being solely dedicated to automotive components. The name SU was brought back to the forefront, and the Company today trades as SU Automotive.

Burlen Fuel Systems, meanwhile, were practically single-handedly responsible for the re-emergence of the SU brand after its many years of neglect. They upgraded the image with the new SU blue livery and first promoted the product at Autoequip in 1987, followed quickly by several other UK shows and the prestigious 1988 AutoMechanika in Germany.

1994 saw the end of an era of carburetter production for the great marques of motoring manufacturing, when SU ceased original equipment carb production. On 16th August the final units, designated HIF and KIF, were produced, direct descendents of the original design by the Skinner brothers, the longest-running UK carburetter in production. Aftermarket product will be available for decades to come, however, due to the relationship between SU and Burlen Fuel Systems, while low-volume production will continue on a batch basis using production modules at both SU and BFS; indeed, BFS are continuously expanding their range, details of which you will find in this catalogue.

Meanwhile, with their own design and development resource, SU is developing new materials and products for the 21st Century, including plastic throttle bodies, plastic and aluminium fuel rails, lightweight aluminium fuel pumps and electronic fuel injection assemblies.

Burlen Fuel Systems now supplies most of the SU aftermarket requirements, being responsible for kit packing, cataloguing and sales promotion throughout the world. BFS has invested heavily in tooling, both in its own right and in joint ventures with SU Automotive in order to support the Classic market; the most recent example being the re-emergence of OM, HV3, and H Type carburetters.

Burlen Fuel Systems is dedicated to ensuring the long term supply of genuine SU parts for your car. All BFS's SU products are packaged using the SU logo and all literature contains both the SU and the BFS logo - this is your assurance of a quality product.

Article reproduced from TRDC Magazine 1995 Edition 3 and by kind permission of Burlen Fuel Systems Ltd.

Burlen Fuel Systems can be found at:-

Burlen Ltd
Spitfire House
Castle Road

Phone +44(0)1722 412 500

Web site:-