A question was raised about the use of the carb adjusting rod and it's effect on overheating.
The adjustment rod controls the fuel entering the carb. The choke controls the air flow.
Together they control the fuel-air mixture entering the cylinders. This is often referred to as the fuel/air ratio.
The engine runs best when the ratio is about 14:1. That is 14 parts by volume of air to 1 volume of fuel (sometimes measured in cubic feet).
Modern gasoline is "oxygenated" to burn cleaner than fuel of the Model A era. This affects the fuel air ratio and creates a leaner mixture. A lean mixture causes the engine to run hotter. In modern cars, the computer takes care of that calculation. In a Model A it is up to the driver to set the correct setting.
Other factors are at play in this scene. Air density is a major part of this equation. It varies due to several conditions.Altitude: Barometric pressure changes with altitude. The greater the altitude the thinner the air.
Less fuel required.
Humidity: More moisture, the air is denser. More fuel required. Athough in this case the moisture does have a cooling effect.
Temperature: Hot air is less dense than cold air. The warmer the air the less fuel required. All this being said the amount of change in fuel consumption will be minimal. Knowing your engine is important. Listen to the sound. If you enrich the mixture and the engine RPM increases you are going in the right direction. If it decreases you are too rich and not getting the optimum fuel ratio. The opposite is also true. If your mixture is too lean the RPM will also drop and your engine will run hotter. This procedure will take a little practice to perfect. The main point being that running the fuel mixture too lean can cause overheating.
Have a safe driving season!
Sid Gough - Technical Editor
