Brauns Auto
LOMITA, CA 90717

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A Primer On Winfield Carburetors

The Winfield carburetors can be broken into a group of categories. These are two fundamental models, namely the S and the SR carburetor. The S carburetor does not have a separate accelerator pump where the SR model has a vacuum operated accelerator pump. Both the float bowl and the throttle body are different for the S and the SR model. Both models had fuel storage wells that are after the main adjustable jet, but the components that are in these fuel wells are different. These fuel wells provide acceleration fuel to the venturies. The S model provides the necessary extra fuel for acceleration based upon the components that are in the fuel wells. Both models use air bleeds that help break up the fuel before it enters the venturies in the throttle body. Winfield actually made adjustable air bleeds but these are very rare and can be difficult to tune. Access to the components in the well is by virtue of the large brass screws on the bottom of the fuel bowl. The SR model has a diaphragm that is bolted to the bottom of the fuel bowl and this diaphragm is spring-loaded and has a check valve that allows fuel to access one side of the diaphragm. When the manifold vacuum is suddenly dropped, as a result of opening the butterfly the spring tension pushes the diaphragm and this action causes a squirt of fuel to be routed into the intermediate fuel path in the throttle body. As a note here, the SR throttle body can be used with an S bowl, provided that the proper components are used in the acceleration wells, but this modification should be attempted only by someone who is very familiar with the workings of these carburetors. An SR bowl will bolt to the S throttle body, but making this combination run correctly is much more difficult and should not be attempted.

Both the S and the SR models were available in updraft and downdraft versions and the fuel bowl is the determining part of the carburetor. The throttle bodies are the same for either an updraft or downdraft model. As an aside, either can be converted to a side-draft version, by virtue of an appropriate cross adapter. The carburetors can have the bowls bolted to the throttle body in either direction, but an updraft must be used as an updraft and a downdraft must be used as a downdraft. They will not operate correctly if the bowl is simply turned over.

With regard to size, the carburetors were available in seven sizes; A, AA, B, BB, C, CC, and D. There were four bowl sizes, namely A, B, C, and D, but the internal acceleration components in the fuel wells in the bowls made the difference between an A and an AA and so on. It is important that the internal components be proper for the carburetors to operate correctly.

The carburetors were originally copper plated, but they were made of pot metal and the plating was not thick and generally did not survive until today. Most of these carburetors have been worked on without the proper tools. As a result, many of the brass components are cosmetically damaged. There were several types of choke stacks available. These were either straight or curved and were available chrome plated or copper plated. When two separate carburetors were used generally only one choke plate was used. There were sets of carburetors that were made in a pair, mounted on a Winfield aluminum manifold. These were made to replace the Stromberg 97 or other large two-barrel carburetors. In this case both choke plates were used, but were connected with one choke cable.

The Winfield carburetors were made to operate with gasoline fuel and the SR model must have new accelerator pump diaphragms that are compatible with today's gas.