Pre Heat Tube or Duct
This component is required on most vehicles with carbureted engines. The pre heat tube is usual a flexible metal duct attached to the engine's air filter housing on one end and an exhaust manifold cover on the other.
The duct is used to deliver heat to the air being drawn into the engine. It is designed to promote faster carburetor and engine warm-ups.
Once the vehicle is at proper operating temperature the passage door shuts, stopping any further warm air from entering the air filer assembly.
If your vehicle is equipped with a carburetor, the pre heat duct or tube will look similar to the image indicated in the diagram below.
Your vehicle's Underhood Emissions label can provide you with information regarding the requirement of this component.
Location: The metal pre heat duct will be attached to the engine's air filter housing on one end and an exhaust manifold cover on the other. If your vehicle needs to be equipped with one, this component will not be difficult to locate.