This series of carburetors is a two-barrel downdraft carburetor used on mainly Ford, Mercury and Lincoln products, including Ford trucks from 1934 to 1956 and GMC, IHC, Mack, REO and White trucks into the 1950's.
Holley 2100 - Ford Car
The best known version is the Holley 2100 used on Ford flathead engines starting in 1934. This carburetor uses a three bolt flange, shared with the Stromberg EE-1 ('97'). This carburetor was produced for Ford and is often found with Ford script markings on the float bowl, in which case it is referred to as the AA-1 model. The 2100/AA-1 carburetors are often referred to as Ford 94's due to the '94' marking on the back of the float bowl, which refers to the venturi diameter in inches.
A similar carburetor was referred to as the Chandler-Grove 91 or 99 model (after the original designer of the carb) and was used on Lincoln V-12's from 1937 to 1948, as well as 1938-1942 90-100 HP Ford flatheads. The smaller 81 model was used on the 60 HP flathead in 1937-1940.
The 2100 DD variant appeared in 1952 and was last used on the 272 CID motor in 1955. The 2110 EE was used in 1956 and 1957 in Ford trucks in 1956 and 1957. These used a conventional four bolt flange.
Holley 852 FFG
Governed versions appeared on heavier trucks in the 1950's. GMC and REO trucks used the 852 FFG carburetor, which was similar in layout to the AA-1. IHC used an AA-1G and Mack used an AA-1. The designation AA-1G denotes a carburetor with an integral governor, whereas an AA-1 could be used with an inline governor mounted under the carburetor. Most of the medium and heavy truck versions of these carbs used a cast iron airhorn and throttle body, but a zinc float bowl.
The 852 series of carburetor should not be confused with the 885 model, which are 'concentric' or 'Tea Pot' models, described here.