The ECB-B four barrel intake was originally designed for the 1955 models. It’s easily recognizable by the vertical flat on the right side of the intake for the automatic choke hardware. The '56 models had the automatic choke hardware moved up to the carburetors. Here’s the link to a past thread giving some of the casting numbers for the more common four barrel Y intake manifolds.

http://forums.y-blocksforever.com/FindPost37008.aspx

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Here’s also the link to a past thread showing the dyno results between the 1956 and 1957 intake manifolds.

http://forums.y-blocksforever.com/Topic77765.aspx

Lorena, Texas (South of Waco)

I have an intake I believe from a 1956 Mercury 312 engine can anyone tell me different & is this a good intake as being a 4BB number stamped on intake is ECB 9426 B
Thank you in advance for your input.
Old Gasser (Ron)