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#14161
BRIAN MARSHALL
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The earlier versions of the Scott-Amal type 6 and type 29 had an external primary inlet system, with four external holes in the side of the body. The specifying dept. of the armed forces vehicle procurement did not like this feature, and sensibly insisted that ALL air entering the carb could be filtered. The carbs were therefore modified, with an internal primary air inlet just inside the main air inlet, near the bellmouth retaining thread. Jet blocks are totally different between the two types, and not interchangeable. I think that this major change occured somewhere around 1938. Jet sizes stated prewar and postwar are no longer relevant because petrol is totally different. For instance if it stated a 170 main jet, you will need a 190 or 200. A type 29, as fitted to the 1939 Clubman Special will need a 210 or 220 main jet if the engine is still in its original ‘specially tuned’ specification, and 596cc.
Brian