Carburettors require a hot spot to help the vaporisation of the fuel or they would ice up especially in cold weather. This can be done by contact with the exhaust manifold as in the Traction or some cars pass hot water from the radiator through the inlet manifold, common with SU carbs. My Light 15 has SU carbs without any heating, so I guess the heat rising from the exhaust manifold is enough.
Cheers Richard
Richard Larter