Carburetor Classics: The Humble SU

Road and Track
In 1926 the growing company was bought by Morris Motors, which expanded production and soon added a line of fuel pumps. During WWII, SU carburetors fed the Hurricanes and Spitfires that won the Battle of Britain over fuel-injected Messerschmitts.


By the 1950s, SU was making 60,000 carburetors and fuel pumps per week in their spacious factory. These were installed on everything from tiny Mini Coopers to booming Aston Martins. The winning Jaguar at Le Mans in 1951 wore SU carbs, as did hundreds of amateur racing cars around the world.


The SU's small, round fuel bowls were extremely resistant to starvation in hard cornering, and they were easy for even amateur racers to modify for more performance. Although less tunable than the more intricate (and expensive) Weber carbs from Italy, the SU was easier to set up and less likely to need adjustment.


Most Americans saw their first SU carbs during the sports car boom of the 1950s. They were mounted on MGs, Triumphs, Austin-Healeys and Jaguars, and usually delivered in pairs on 4-cylinder and 6-cylinder engines. They appeared in triplicate on hotter sixes like the Jaguar XKE, Aston Martin and some Healeys.


The twin carbs were connected by a simple linkage system that could be easily adjusted with a screwdriver. This ease of adjustment led amateur mechanics to attempt to correct any engine malady from an intermittent miss to catastrophic crankshaft failure by turning one or more of the funny little carb screws. When this didn't work, they blamed SU. Not fair.