automatic choke operation

[fordor41]

Decided to hook up the auto choke on my carb (SBF 2 brl). I cleaned out the hole in the exhaust manifold so the heat tube would slide in and noticed that it appears to be a blind hole. how can heat travel up the heat tube to the choke housing to open the choke if the hole in the manifold is a blind hole. I assume there is some sort of vacuum assist from the choke housing but with a blind hole how does the heat travel?