 The 276 type carburettor is, in virtually all aspects, identical to the 76 version, except that the main emulsion air is drawn from inside the air intake (air filter) whilst the 76 carburettor uses unfiltered air.The 76 types are of die-cast zinc construction and were introduced in the early 1930s, replacing the earlier 6 series, which were of bronze construction, although basically the same design.The 276 type was introduced in 1940 in an attempt to improve the carburettor's durability in dusty and dirty operating environments.