The Motorcraft 2100 (often originally branded as the Autolite 2100) is a two-barrel carburetor that was used on many Ford engines from the 1960s to the mid-1980s. The carburetor is known for its simplicity, durability, and good performance.

One of the primary ways to identify and differentiate between the various 2100 carburetors is by the size of their venturis. The venturi size directly affects the airflow and fuel mixture, making it vital for engine tuning and matching the carburetor to a specific engine's needs.

Here's a list of common Motorcraft 2100 carburetor venturi sizes and their corresponding airflow ratings:

1. 0.98 inches - rated at 190 CFM (Cubic Feet per Minute). Often found on smaller engines.
2. 1.01 inches - rated at 240 CFM. This size was used on a variety of mid-sized engines.
3. 1.02 inches - rated at 245 CFM. Another variant for mid-sized engines.
4. 1.08 inches - rated at 287 CFM. This is one of the more common sizes and was used on a lot of Ford 289 and 302 engines.
5. 1.14 inches - rated at 300+ CFM. This size is less common and was found on some larger engines.
6. 1.21 inches - rated at 351 CFM. Typically found on the largest Ford engines that used the 2100 carb, such as the 390 and 428.

Keep in mind that the actual performance and efficiency of the carburetor can be influenced by various other factors beyond venturi size, such as the condition of the carburetor, the altitude, and the specific tuning. It's also worth noting that over the years, there might be variations or unique applications that deviate from the list above.

The Motorcraft 2100 & 2150 use different venturi sizes depending on the engine size. The 2 barrel carburetor will usually have the venturi size stamped on the side of the carburetor (Chinese made carburetors may not). This number corresponds to the measurement at (A). This particular carburetor measured 1.21" which would be used on bigger v-8's aka 390 CID.

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