The problem with water heat is you need the heat the most when the engine is cold. When the engine is cold, guess what else is cold; the coolant! Exhaust gets warmer quicker. Another consideration is that some carburetors need heat more than others. I have switched back and forth between a large venturi monojet and a Holley / weber recently and the Weber doesn't need the heated manifold near as much as the monojet. The weber has a water heated choke, and runs good from the second you fire it up. The monojet has a hand choke and requires considerable babying when I first start the motor cold. I have seen actual frost on the carb base during warm up without heat to the manifold. Now in a case like that exhaust heat is best becuase it is warm right away.
Boo
