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
Jerry the butterfly assembly was fubar and had been previously removed/butchered so I also removed the riser pipe and as you saw plugged the holes,i'm running an Edelbrock 1406 4bbl with electric choke and have never had any issues without preheat,even down as low as the mid 20s degrees.
It was simply an easier option for me than trying to find a functioning set up here in Blighty.
