Carburetor Icing

There is one trait this carburetor has, that has given me problems. Although this carburetor does have a choke for cold starts, it suffers from icing. I live in the Seattle area which is cool and damp in the "winter". Once the temps get down to the 30s and it's raining, the carburetor begins to severely ice up. Once the carburetor is iced up, the engine usually won't idle and will die at stop lights. Once it stops running you pretty much have to wait until it thaws out before a restart. This means keeping your foot on the throttle to keep it idling. This does require a different driving technique when coming to a stop. You end up having to keep your right foot on the throttle (after shifting into neutral) to keep the revs up, while braking with your left foot.

Of course once enough heat rises from the engine to warm and defrost the carburetor, everything works okay.

I remember once when the temperature went down to the low 20s and high teens, and it iced really badly. There was enough white frost built up that I could scrape enough off to make a slushy! The throttle even stuck and I had to pull over and shut the engine off. After about 5-10 minutes, the warmth of the engine and exhaust rose to defrost the carb and then it ran okay.

Even on very warm days if you put your hand on the upper part of the intake manifold, you can feel it get really cold when the engine is first started. This is definitely not the carburetor for someone who lives in a cold climate or an area that has real winters. I don't think that having an engine block heater will help either, as those only heat the coolant and won't warm the manifold or carburetor much. It's not too surprising that this system was developed in southern California.

When I used this for my daily driver, I made my own hot box to draw warm air from the headers to the air filter. I purchased some scrap aluminum and built a box that I bolted around the headers. I attached a hose to this, which connected to another piece of formed aluminum that was bolted to the air cleaner cap. Although this helped considerably, it did not cure the problem. At least I never had the throttle stick again.