When starting an engine equipped with a carburetor air heater, in what position should the heater be placed?

The appropriate position for the carburetor air heater when starting an engine is full cold. When starting an engine, particularly in cold conditions, it's beneficial to have the carburetor air heater set to full cold. This allows cold air to enter the carburetor, which is denser and contributes to better fuel atomization and engine performance during startup.

Heating the air at the point of startup can lead to improper fuel mixture ratios, often resulting in a lean mixture that can make starting difficult or cause the engine to run poorly. Therefore, maintaining the heater in the full cold position during this phase optimizes combustion efficiency and helps ensure a smoother startup process.

As the engine warms up and reaches its operating temperature, adjustments may then be made to the carburetor air heater for optimal performance under normal operating conditions.