FROSTY CARB ON U MOLINE

Carb icing is hard to eliminate. But if it causes problems (rough running, stalling, etc) you can minimize it's effects:

Upon initial startup get the choke full open as quick as you can. Soon as the engine starts bump it up a few hundred RPM above idle while the engine warms up. Or better yet put it under light load immediately. Adjust the carburetor for the best idle when warm (an too rich idle misture aggravates carb icing). If the manifold has an adjustable hot spot or heat riser, set it to the "hot" or "winter" position. Having working thermostat in the cooling system is a must - the hotter the better!

In severe cases you can duct hot air from above the exhaust manifold into the air cleaner inlet to warm the air to the carb. Also put a winter front over the radiator in cold weather to stop the constant blast of cold air off the fan from cooling the carburetor.

The reason I ask is if you have an LP manifold on it, there is no provision to conduct any heat down to the carb., like the gas manifolds had. If you notice, about all the MM gasoline manifolds were bolted to the exhaust manifold at some point.

Also, anytime there is a pressure differential in the air flow from high to low pressure the air absorbs heat, the result which you see as frost.