Air Intake System

Fig. 38 Air intake control system.:

This system, Fig. 38, maintains fresh carburetor intake air at approximately 100 degrees F regardless of outside air temperature. When cold, a bleed valve in the air cleaner is closed and manifold vacuum builds in the system, opening a diaphragm actuated door which allows preheated air to enter and blocks outside air. When hot (above 100 degrees F), the bleed valve opens and manifold vacuum escapes, repositioning the door so that ambient air enters and preheated air is blocked. A check valve prevents vacuum pressure loss to the intake manifold at wide-open throttle. A fixed orifice prevents rapid pressure changes and allows smooth operation of the valve door as well as maintaining the proper fuel/air ratio.