The carburetor is the unit that introduces the fuel and air combination into the engines suction (intake) side.  The proper ratio of fuel vs. air is critical to maximize performance.  Too much air causes the engine to starve and run "lean", creating excessive amounts of heat and the potential for damage to occur.  A rich mixture (too much fuel vs. air) causes poor performance (because too much fuel can't burn) as well as a build up of carbon (unburned fuel) throughout the engine and exhaust system.  Although the S.U. carb is a bit primitive by design, it really works the best without too many problems.  Matching the proper size carbs and changing the jets and needles can easily be done.  With the help of a little modern equipment, we analyze the exhaust gasses and determine the ratio of fuel to air and then adjust accordingly.  With the addition of performance camshafts, pistons, and larger exhaust systems, the engine will require more fuel faster, but still, at the same fuel to air ratio.  There are different size needles and jets that will allow a normal amount of fuel at idle,  but add more fuel upon acceleration.  This is critical or the engine will develop "flat spots" or "hesitate" upon acceleration.  The engine will hesitate until the fuel catches up with the air or vice-versa.  So, basically just adding more fuel really doesn't accomplish much, except to flood the engine, foul the spark plugs and carbon up the exhaust system.  A performance engine is a high powered engine that runs efficiently, developing more horsepower faster while still maintaining the proper fuel to air ratios.  By enlarging the carb body from 1 ¾" to 2" we now have the ability to allow more air to be moved easier and faster, depending on the internal workings of the engine.  The S.U. carburetor is a suction type carburetor, which means the engine has to "suck" the fuel/air mixture from the carburetor.  So, by making more fuel and air available to the engine it allows the engine to reach it's potential.  Quite simply, more air can be moved through a 2" hole than a 1 ¾" hole, thus the engine is allowed to respond faster and easier.

OVERALL APPEARANCE:
Just stunning!  With the alloy suction chambers polished to a mirror like finish the S.U. carb is "pure artwork".  Their overall appearance is like no other and a wonderful example of British workmanship and design.  At Jaguars Unlimited we plastic media blast the carb bodies, which give them a flat smooth finish, and to contrast, we polish the suction chambers to a mirror like finish.  We also polish the brass pivots and cadmium plate the linkages, and the fuel lines.  Our carbs look as good as they perform.