The following pics show a couple of original era aftermarket cast iron intake manifolds for Model A & B Fords. The first is a Simmons Swan intake which is an updraft along the lines of a Model A, but with a slightly larger bore, and a higher turbulence balance tube. It was originally claimed that this would provide more even charge loading.
The second manifold shown is a Bendix Stromberg downdraft, though this particular one is not marked. I have another near identical one which has the name cast in.
Simmons Swan. This is a heavy manifold. Note the carb throat transition from round to square. Also has original style vacuum port for wiper. Original Zenith carburetors fit this manifold.
Original Model A style hotspot and exhaust mounting. Large size square runners.
The vertical tube is 1-1/4 inch ID compared to original Model A size of 1-3/16 and original Model B size of 1-5/16 inch ID.
Pictured above is a Bendix Stromberg downdraft. The vertical tube is 1-7/16 inch ID compared to original Model A size of 1-1/4 and original Model B size of 1-5/16 inch ID. It also uses a larger 2-11/16 inch bolt pattern to fit the Stromberg DCX2. The studs are 3/8 inch diameter. This has an original style vacuum port for wiper.
This pic shows the hard turns and also the through-boss for the throttle linkage bellcrank. Original Model A style hotspot and exhaust mounting also.
This is perhaps the most interesting feature. Both runners have a factory drilled 3/64 inch bleed hole at the bottom of the casting. Presumably to drain flooded gas. I wonder whether these holes stayed open or plugged up, and how it affected idle mixture over time?
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