SU Carbs - The history
Practically every Mini owner can name the brilliant engineer responsible for our obsession. Many can name the man responsible for the rubber suspension spring. A goodly number know a fair bit about the engine's heritage and the man who came up with the extremely efficient cylinder head design. They account for the biggest chunks of the Mini's anatomy. But what about that other extremely simple yet hugely effective instrument that features so prominently when engine tuning occurs - the SU carburetter? A limited few can tell you what 'SU' stands for, extremely few have any idea of its concept and evolution. So let's put that right…
In the beginning
Strangely enough, it all started way back with William Banks Skinner; one of the owners/directors of the well-known Lilly and Skinner footwear distributors. In April 1872, W B Skinner's wife gave birth to George Herbert Skinner in Ealing, London. As usual in those days, the inevitable happened - Herbert followed his father into the footwear business. This was only a day job though as his passion was really for the motorcar. Educated locally, no technical schooling was known to have occurred - it didn't stop him submitting three provisional patents for his ideas by 1900. The course seemingly set!
Apparently in 1903 Herbert took a sojourn to France to learn to drive a car - bit different from belling your local BSM, eh? 1904 saw him get together with younger brother Thomas Carlisle (where DID they get these names from?) Skinner - born in Ealing, June 1882 and educated in Cambridge although, again, no technical instruction seemed to have taken place - and a decision was made to pool their thoughts on carburation improvements and get them into practice using a 'Star' motorcar they owner then. The carb fitted as standard had a glass top through which the fuel flow from the jet feeding the engine was visible. They determined that the suction (depression) on the jet varied in accordance with engine demand and decided it would be far more effective if this jet was located in an air channel whose size varied to suit differing engine speeds/loads, so a constant depression and air velocity could be ensured. Testing a quickly made prototype revealed a loss of overall performance - if the mixture was set to give best performance at high rpm, it was way out at low rpm and vice-versa. To correct this problem, they decided a tapered needle to vary the size of the jet orifice was the way to go… 'Can ya tell what id is yit?'…
Herbert applied for a full patent on this in February 1905, which was granted in January 1906 - with his occupation still being stated as 'Boot and Shoe Manufacturer'!
Carl followed Herbert into the family shoe business, but his practical engineering prowess that enabled him to put his inventive genius of a brother's ideas into reality lead him to join R P Wailes to make and fit carburetters. Actually when the first carbs were produced is a bit of a grey area, but it's very likely they were made at George Wailes & Co.'s works at 258, Euston Road, London. George Wailes sold his works and premises in 1906, subsequently Carl joined up with George's son, taking temporary premises in Euston Buildings whilst new works were being built at 386-388, Euston Road. Another of the Skinner brothers appeared on the scene around this time - John (blimey, what were his parents thinking? Giving him such an ordinary name!). His input is unclear other than he had become a director by about 1913.
For some years, Herbert's sketches where committed to working drawings by the chief draughtsman - a Mr. J O Gardner - then manufactured and consequently fitted to a wide variety of individual cars all in the new works three-story building. Herbert ploughed his efforts into design and development and also in patents to protect his creations - furthering the all ready granted full patent for the 'constant depression' carb idea to cover Belgium, France, Germany, Italy and the USA. Neatly nipping in the bud the countries most prolific in early car development. A clever bunny or what? Herbert's prolific mind encompassed not only the SU carb but other inventions too - a hydraulic variable speed gear, a detachable strap for ladies court shoes and slippers (eek!), a paraffin and an aero carburetter and a supplementary fuel supply valve for cold starting. A veritable explosion of new ideas.
Apparently originally branded 'The Union Carburetter', it was soon re-named 'The SU carburetter', being an abbreviation of 'Skinner's Union' - the brotherhood. Well, there was three of them…
1910 saw the company move to 154, Prince of Wales Road, Kentish Town, North London and The SU Company Limited was born on the 2nd August 1910, company registration number 111416. Interestingly the earliest financial records show what a wonder these carbs were - and what a fortune they were making the company… directors fees in the ledger dated April 30th 1911 show the princely sum of £25 each paid to W B Skinner, G H Skinner and J H Skinner. But no G H Skinner…The accounts also showed Woleseley and Rover were regular customers - shades of things to come.
Originally the carb was fitted with a leather bellows where the dashpot now resides on the latest incarnation. They required regular application of glycerin to maintain their suppleness, and proved very effective given materials technology at the time. Kid goatskin was used, manufactured by Herbert's wife, Mabel (well, what did you expect?) from their home - a cottage industry none-the-less! Again, old accounts show Mrs Skinner provided these bellows right up to 1928. Although in later years they would have been as service parts rather than production.
1914 and World War I saw carb production massively reduced as the factory became seconded by the government to knock out machine-gun parts, bombs and aircraft carbs. With cessation of hostilities came the resurgence of carb manufacture - but much depleted because of the post-war recession within the automotive industry. However, car manufacturers of the quality and magnitude of Bentley, Invicta and Napier recognised the SU's benefits, fitting them to many of their models. At this time the leather bellows was replaced by a brass piston.
By the mid twenties, William Morris (Morris Motors) was fitting more and more SU's to his cars. In fact he liked the product so much, he bought the company. The Skinner family was relieved as keeping the SU Company afloat - something they'd been doing for many years - was proving costly. The company was immediately transferred to works premises in the Midlands - the Woleseley factory at Adderley Park, another of Morris's acquisitions. Carl was retained as Managing Director. SU production boomed with the whole Morris Empire to service, development seeing a surge, as money was no longer an issue - new products coming thick and fast. 1929 - the HV type carb was designed featuring a bottom feed float chamber. The 'Petrolift' fuel pump saw the light of day - the very successful forerunner to the SU electric fuel pump, replacing the gravity and vacuum fuel tanks used at that time. 1930 - the HV was modified to have a top feed float chamber. 1931 - the OM and D type carbs appeared, the D standing for 'down-draught' - the design using a spring in the suction chamber to return the piston to the idle position; sound familiar? Unfortunately 1931 also saw the death of Herbert, sadly never to see the hey-day of his inspired invention. 1932 - and SU's first aero carb developed from these previous designs was sold for military and civil aircraft use during the mid to late 1930s; including the Rolls Royce Merlin engine. 1933 and the L type petrol pump was born to replace the Petrolift and is still in production today - the same design used on the first Mini Coopers!
SU Carburetters Limited and WWII
1936 and the company became SU Carburetters Limited. 1937 was the year the ubiquitous H-type SU carb was born featuring a range of choke bore sizes from 1-1/8 inch to 2 inches in 1/8 inch increments; a carb to cover all applications and so successful was the design it stayed virtually unchanged right through to the end on the 1950s. 1938 and the only modification to the H-type - the addition of the hydraulic piston damper to improve acceleration enrichment, a feature that remains right now. SU was thriving - supplying either fuel pumps or carburetters, and sometimes both, to nearly all models in the Morris, MG, Riley, Woleseley, Alvis, Bently and SS. Contemporary reports show some 4,000 pumps and 4,000 carbs were being manufactured weekly by some 400-4540 employees at a 81,000sq ft factory. Brass replaced the die-cast zinc piston as it was discovered the zinc item grew or distorted with age, causing loose piston rods. The HV carb was finally phased out. Then World War II exploded on to the scene.
SU's expertise was pounced upon to produce all aero-carbs for Rolls Royce Merlin, Vulture, Peregrine and Napier (for their Sabre and Dagger engines) as well as fuel pumps for the military - swelling the workforce by nearly 100%. Luckily an on-the-ball government bod spotted the danger of having all this production in one place and a second factory was set up in the Riley works in Coventry. Good job too, as in November 1940 an air raids caused damage to the main factory - a fire contained by the work's fire fighters, three direct hits scored by high explosive bombs. Despite the machine shop getting the brunt of it the carb production line survived. In subsequent raids, no bombs hit the factory but all manner of debris from exploding surrounding buildings came through the roof. The Ministry for Aircraft production thought it prudent to evacuate the factory. In true Brit grit stylee, within 12 hours the first RAF trucks arrived to instigate the move to a newly built, modern factory at Highlands Road, Shirley (requisitioned from the Co-Op!). Production carried on throughout the move, any voids being filled by the Riley-based shadow factory. Production escalated to meet the demands of war, often seeing the workers voluntarily stretching their normal working day of 8am-7pm to the point where they'd be sleeping on the floor next to their machines. Doesn't it make you proud?
1941 and a boot factory in the Yorkshire village of Barwell was requisitioned to form a second shadow factory. Here they not only turned out the SU, but also the Rolls Royce Bendix Stromberg type carb. 1942 - the petrol injection pump was developed for aero-engines, first fitted to the monstrously quick Mosquito aircraft (633 Squadron and all that). An effective design - like many things since ended up in the hands of an American company (called the Simmonds Injector Pump) because nobody in British industry saw it's potential. Ho-hum.
Post War blood rush and decline
Unlike the follow-up to WWI, post WWII witnessed strong and steady growth. 1945 - pumps and carb s production resumed. 1947 - the expanding company moved to new premises at Wood Lane, Erdington, Birmingham. Morris (Lord Nuffield) assembled eight senior figures from various parts of the Nuffield empire along with Carl Skinner - now 65 years old - and announced their retirement, thus finally ending the Skinner connection and a career dedicated to the on-going development of his brother's ingenious invention. It didn't stop the development though…
1948 - aluminium die-castings replaced zinc and brass, a direct result of experience gained throughout the war years. A mountain of aluminium left over from aircraft production ensured constant supply. 1950 - introduction of dust proofing. 1952 - BMC (British Motor Corporation) was formed, expanding SU requirement. 1954 - introduction of the part throttle weaker on single carbs on six-cylinder engines and the HD type carb was born. 1958 - the HS type carb was born; unfortunately it is the year Carl Skinner died. 1962 - the delrin float needle appeared. 1963 - nylon floats for HS carbs. 1967 the first of SU's mechanical fuel pumps and an automatic enrichment device. 1969 - the spring loaded needle and throttle over-run valve were introduced. 1971 - jet temperature compensation (the pesky 'wax-stat') appeared. 1972 - first HIF types surfaced. 1975 - pesky Wax-stat appears on HS4 and HS6 types. 1976 - ball-bearing suction chamber/rods added.
1976 and the diabolical monster that was British Leyland motor Holdings was falling apart, dragging down all it's connected small plant manufacturers - of which SU was one. Hoving off chunks of the BLMH Empire to try and salvage something saw SU sold into the service and parts division, renamed SU/Butec. 1982 - the last real development added the HIF44E with electronic control of cold start, idle speed and overrun. A few years later and SU/Butec dissolved into Austin Rover Fuel systems - SU's identity seemed lost forever and service parts became sporadic. 1988 - Hoburn Eaton Group bought the company who were in turn consumed by a multinational USA company called Echlin Corporation who were later swallowed up by the giant that is Dana Corporation. In 1998 the company became Dana SU Automotive.
SU carb saviors
Things were starting to look seriously bleak in the mid eighties when twin SUs as used on MGB, Midget, Spitfire, etc. were threatened with extinction. Enter stage right - the knights in shining armour, Burlen Services who persuaded Dana to keep the tooling operational. Formed in 1971, they became involved with SU carbs during the 1974 fuel crisis. A period of mutual co-operation and benefit followed. In 1986 Burlen started trading under 'Burlen Fuel Systems. Their massive efforts and dedicated input caused the re-emergence of the SU brand.
1994 was the end of SU carb production, the end of an era when SU ceased to be original equipment supply - the longest running production of a UK carburetter. Fortunately the intervention and dedication will keep SU products available for decades to come. In 1996 they have taken over exclusive manufacture of all SU carbs and pumps - bless their cotton socks. The SU may be nearly a century old design - but it is so effective and simple it has a real future - especially where our good old A-series is concerned.
BFS supply SU components to many of the major Mini parts suppliers. If you cannot get what you need from them, Burlen Fuel Systems are at
Wilts SP1 3SA
Tel: 01722 412500
Fax: 01722 334221