mylifeswork wrote:The engine does make more power with a dense air/fuel ratio. I'm sure we all want more power. The problem is when the air gets colder, more dense, the carburetor doesn't compensate with more fuel. So the overall air/fuel ratio is leaner. More air but not more fuel. that's why we went to computerized fuel injection so we could adjust air/fuel mixture at will based of temperature, altitude and any other conditions the computers sensors could monitor. Carburetors for the most part are dumb. They don't know when the engine has a vacuum leak. They don't know when the altitude has changed. They also don't know when the temperature climbs or drops. This was one reason for trying to maintain certain air temps through the air cleaner so the jets and tuning of the carburetor would be compatible for proper fuel mixture regardless of outside air temperatures. Not to rich and not to lean. We still need chokes during cold weather conditions but when the air temperature and engine temperature is where it should be the choke is shut off.
If we want to tune our carburetor everytime we go into winter and back in the summer that's fine. I'm sure most would rather enjoy driving their truck instead of constantly tuning for all the changes we drive them in. Colder air/fuel mixtures are great and make more power. We just have to be able for the carburetor to provide the extra fuel when the colder air is provided. That's why they have chokes on them. When the air temp and engine temp is cold. Usually we need to re-jet a carburetor when the heated air cleaners are removed since the factory calibration is set for the higher air temps provided by the air cleaner system, all for better emissions and fuel economy. Once we remove the heaterd Air cleaner system we need to compensate with more fuel for the colder air. I hope this makes sense. I don't mind sharing any information or answering any questions. I know we all are trying to understand and learn as much as possible about our trucks.
This holds true in most cases, but none of this is the cause of carburetor icing. Keep in mind while reading the following, we're talking cool temperatures and high humidity.
What happens is that the air outside of the engine is at ambient barometric pressure (~29 in Hg at sea level).
The fuel-air mixture that enters the intake manifold is at a highly-reduced pressure. In fact, it's going into a vacuum, about 15-18 in Hg at idle.
(Before you flame me about the 29 in Hg vs 15-18 in Hg, remember that one is pressure and the other vacuum, and both are measured on the same scale, just in opposite directions from zero, so we could have nearly 50 in Hg difference in pressure)
Since air is composed of gases, it reacts the same as any gas when it goes from a high pressure to a low pressure -- it cools. This is the same principle that enables air conditioning units to work.
The coolest point is right where the pressure drop occurs. In this case, it is at the throttle plates in the carburetor. (Ever watched the area around an expansion valve on an air conditioning system? When operating in a high-humidity atmosphere, the line starts frosting up right at the valve and migrates away from the valve.) When this icing occurs, it clogs up the holes around the mixture screws, blocking flow, and causing an over-rich condition. It also causes ice to form on the throttle plates.
Heating either the incoming air or the base of the carburetor prohibits the formation of this ice.
I intend to do a 195 thermostat and install heated 1" spacer,if i recall correctly the spacer is on the heater circuit so it is only hot when the heater core is,so it can't hurt 
