The SU Carburettor
Those of you of a certain age who visited or originated in the UK will be familiar with the chain of shoe shops called Lilley & Skinner which were a common sight in the High Streets of most towns. This shoe business was started in 1835 by one Thomas Lilley.
In 1881 he was joined by William Skinner and some 25 years later younger members of the Skinner family become involved. Three Skinner brothers in the family – Herbert, Carl and JH – also dabbled in engineering and in the early 1900s set up a company to serve that new-fangled invention, the motor-car.
One of the difficulties with engines of that era was the fuel system; particularly the means of getting the right amount of fuel into the engine with the right amount of air. You only have to look at the early vehicles to see how basic this was. The boys put their collective minds to work, to address this challenge.
The device patented by Herbert Skinner in 1905 was a tapered needle mounted in leather bellows of the best quality, made by a family member in the shoe business. The bellows and needle were enclosed in a chamber attached to a tapered tube (venturi) clamped to the inlet side of the engine. As the engine speed increased, so did the airflow through the venturi, lifting the bellows and tapered needle and thus allowing more fuel mixture into the engine.
Thus the SU carburettor was born: S for Skinner and U for the union of the three brothers.
By 1912 they had a flourishing factory in London, producing carburettors in quantity and switched to military production at the start of WWI, including carburettors for aero engines.
The original SU design had no choke. In 1918, Wolseley Motors patented a solution by adding a moveable jet, operated by the driver. This can be a source of rich running if the choke cable is not correctly set up to allow the jet to return to its proper position.
After the War, SU carburettors were being supplied to Wolseley, Austin, Lagonda and Napier. In 1920, the first carburettors and pumps were supplied to Morris Motors, increasing production considerably.
In 1926 the company got into financial difficulties, so Herbert left and Carl sold the business to William Morris for £100,000. Morris relocated the factory to Birmingham and, at this time, Morris Motors required 1000 units per week.
Expansion allowed the company to develop new products, including the Petrolift pump and aero carburettors: one version of which was fitted to the Rolls Royce Merlin engines that powered the Hurricane, Spitfire and Lancaster.
With the outbreak of WWII, production facilities were duplicated at Riley Motors in Coventry. The Birmingham plant was bombed and relocated elsewhere in the city. Another factory was established, to make aero engine components, including a fuel injection pump for the Merlin engine.
In 1947 the original Birmingham factory reopened once again, making 223,000 carburettors and pumps per year. Carl Skinner returned at the end of that year and sold the fuel injection side to the Stirling Company in the USA.
With the formation of BMC in 1952, SU production once again increased. In time, the Zenith carburettors and AC mechanical fuel pumps fitted to the Austins were replaced by SUs. The evidence of the latter items can be seen on many B -Series engines, where a blanking plate covers the hole in the block where the actuating lever for the AC pump engaged an eccentric on the camshaft. For years the camshaft continued to be produced with the unused eccentric, because it was too costly to change the tooling for the forgings, for no purpose.
With the creation of British Motor Holdings (BMH) in 1965, some 30,000 carburettors per week were required for all marques in the group, including the new HD and HS types, and the HIF that had an integral float and electronic cold-start system.
In the mid-80s, with technology changing rapidly to fuel injection, SU production changed to Single and Multi Point Throttle Bodies.
After a further change in ownership, in 1988, from BMH to British Aerospace, SU was sold off to the USA’s Hoburn Group; in turn acquired by Echlin Inc, which was later taken over by Dana Inc.
At the end of the 1990s, negotiations were completed with Burlen Fuel Systems Ltd in Salisbury, England, to manufacture and supply spares. This company is now the primary source and has a good website. Reasonable prices and a reconditioning service are offered, so check it out at www.sucarb.co.uk