Throttle Closure Delay System

To control emissions during deceleration, throttle plate is held slightly opened by means of a vacuum operated diaphragm unit. At a speed of over 1750 ± 100 RPM (4 cyl. models) or 1920 ± 100 RPM (6 cyl. models), speed sensing relay actuates two way valve to vent vacuum diaphragm unit to atmosphere. A spring, in vacuum unit, then causes carburetor linkage to open throttle 3-4°. As engine speed drops below 1650 ± 100 RPM (4 cyl. models) or 1800 ± 100 RPM (6 cyl. models), relay interrupts flow of current to valve. This allows intake manifold vacuum to retract plunger of vacuum unit and return throttle to idle position.