Carburetor Classics: The Humble SU

Ask many former owners of 1960s British sports cars about problem areas on their steeds, and they will likely digress into horror stories concerning the dreaded SU carburetors. In most cases though, they'd be wrong.


The SU carburetor, far from being high maintenance or temperamental, is one of the best designed carburetors of all time, and it simply thrives on neglect. In fact, the principal reason it is blamed for so many maladies is that it is conveniently perched beside the engine where it can be easily misadjusted by ham-fisted mechanics often unaware that the real gremlins usually live in the worrisome Lucas "Prince of Darkness" electrical systems common in older British iron. Those in the know realize that the humble SU can be made to feed anything from economical grocery-getters to fire-breathing racing cars. Some lemon!

Two Brothers
The SU Company was formed in 1910 by two brothers, George Herbert and Thomas Carlyle Skinner, who named their company Skinners Union. They had been very successful in the family shoe and leather business, but were captivated by the primitive cars starting to rattle down English lanes. The carburetors of the time were Rube Goldberg devices, requiring separate hand controls for varying gas flow and air mixtures.


George Skinner came up with an alternative in 1904, introducing a carburetor with a floating piston mounting a long tapered needle that moved up and down inside the fuel jet. A leather bellows that responded to engine vacuum actuated the piston. This carburetor was well-received, even though it was expensive to produce.


Then WWI intervened, and SU made military equipment and did general engineering work until 1925 when the company introduced a new carburetor, built on the same principals but without the leather bellows. In its place was a bell-shaped aluminum "dashpot" on top of the carburetor in which the piston slid up and down. This setup was to become one of the most successful carburetor designs of all times. It was used by the fabulously expensive Bentleys on both road and track (where they won Le Mans five times), and by low-priced marques like Wolseley and Morris as well.