Thanks for that. Both my twin HS4 setup and my Weber 28/36 DCD setup used to ice up until I connected the heater pipes to the manifold. That was a 997 Cooper with a 544. If you Google Icing of carburetter then there's loads of info available.God there is some crap in this thread.
It is purely an economy device. It has nothing to do with condensation or icing on the carb.
The carb is thermally insulated from the manifold. That is why the spacers are made out of a plastic. So any heat that is put into the system is only going into the manifold.
The original cast iron manifolds were joined and do had their own hot spot. This does help with the fuel atomisation and the cast iron set up has been shown to be better than the water heated one for the first few minutes of running but the water heated is better from then on it can also help smooth out the tick over at idle.
But it has an effect on raw power output.
Connect or not is up to you but note that if you have a heater unit that you control the water flow for temperature control rather than one that uses air flow your heated manifold is unlikely to be doing much as the flow will be off.
The Metro had a metal pipe that ran across the back of the block to return the coolant back to the hoses which if it can be found keeps things tidy.
Never sees any twin carb inlet with water heated set up.
Never had issues with my twin 1 1/2s or my DCD on my 1380 with 286. Did have the carb freeze up on the pick up one winter. Put me in a ditch. Playing in the snow in th Pennines is fun.
Sorry Nicklouse the twin HS4s didn't have a heated manifold which was part of the reason to go to the DCD. My freezing used to be on MN all night events in south/west wales and on Epynt. Yes, playing in snow is great fun, even more so in an artic!
