The Stovebolt Site Forums The Shop Area Engine Shop Heat Riser...?

You need heat to provide vaporization of fuel and to prevent carb from freezing up. Carbs can freeze up on a 100+ degree day. Also needed to improve performance and save gasoline. The only situation where heat is not needed is on the salt flats where the engine is consistently operated with the throttle wide-open.

On the other hand if you are using exhaust heat without the heat riser thermostatic spring fully functional you will have too much vaporization, poor combustion, poor performance, and wasted fuel. In addition your carbs will eventually be destroyed from being way too hot for extended periods of time.