The Zenith model TU is a series of one barrel carburetors with an unusual design where the float bowl is a separate assembly that may be mounted in any one of four positions to provide downdraft, updraft and sidedraft (horizontal) operation.
The updraft configuration of model TU has the throttle at the top and the choke plate at the bottom. The float bowl is shown on the right hand side above. The air inlet is at the bottom and the manifold flange is at the top.
Various versions of the Zenith TU series were used on a number of different industrial applcations from the mid 1930s to the early 1960s. A noteable example are the model TU3-1/2 and TU4C which were used on Caterpillar diesel pony (starting) engines from 1936 to 1961.
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How to find Zenith carburetor numbers