Are you referring to the piece of tubing that goes through the passenger's side manifold at approximately a 45 degree angle? That was intended to be an air passage for the choke heater on an automatic choke carburetor. The heat riser passages go through the cylinder heads and intake manifold. Unless you have the add-on flapper valve in one of the outlets, there's very little flow through those passages, and virtually no carburetor heating during warmup.
Jerry

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