Brian
One of the best sources of information about the Series 1 in the world resides on your continent , John Merton is listed as the Series 1 contact in the Oz club magazines , and although I am pleased that you feel that TM can give you the answers you need, a call to him might have given you the data "locally".
Anyway here are his comments:
The pipe he's talking about is simply a drain pipe down from around the sharp bend in the inlet manifold just under the carburettor. The two centre exhaust manifold pipes have take-offs to this point creating a hotspot to help fuel vaporisation. Basically, while feeding cold air into the carb is better because it is denser, once it mixes with fuel in the carbie it both vaporises it(i.e. the fuel mixture) and there can also be some atomisation (i.e. small droplets of fuel, which can puddle on the floor of the inlet manifold where it takes its sharp turn inwards under the carburettor towards the cylinder head. The purpose of the hot spot is to help revapourise any such petrol puddles.
Trust this and Rob's pictures answer you query.
