See Figure 1
This system is used only on carbureted vehicles.
A high altitude compensation system is installed on California vehicles. This modification affects the primary metering system as follows:
A small cylindrical bellows chamber mounted on the body panel in the engine compartment and connected to the carburetor with hoses, is vented to the atmosphere at the top of the carburetor. Atmospheric pressure expands and contracts the bellows.
A small brass tapered-seat valve regulates air flow when it is raised off its seat by expanding the bellows.
If the car travels to a mountainous area, rarefied atmosphere is encountered, producing a rich air/fuel mixture. At a predetermined atmospheric pressure, the bellows opens, allowing additional air to enter the main air bleeds. The auxiliary air, along with the air normally inducted by the carburetor provides the system with the proper amount of air necessary to maintain the correct air/fuel mixture.