Ford's 289 engine came with a single carburetor in 1966. A carburetor is most commonly associated with preparing the combustible mixture of air and fuel required by the engine, but the carburetor also determines the speed at which the engine idles. If the idle speed is set too low, the engine may have difficulty idling and may even stall. If the idle is set too high, it will be necessary to press the brake pedal harder than normal to prevent the vehicle from rolling forward when in gear. Fortunately, adjusting the idle speed on the 1966 289 is a fairly straightforward task.
Turn the engine on and let it run until the engine warms up.
Pull the single vacuum line off the side of the distributor.
Insert a screw, nail or similar object into the opening on the distributor's vacuum hose to plug it.
Locate the idle setting screw on the driver's side of the carburetor, on the front of the accelerator linkage.
Start the engine and read the vehicle's tachometer to determine the current engine speed.
Adjust the idle to the appropriate specification by turning the idle setting screw with a screwdriver. Turning the screw clockwise increases the idle speed, while turning the screw counterclockwise decreases the idle speed. Adjust the idle speed to 700 revolutions per minute if the car is equipped with a manual transmission and 550 revolutions per minute if equipped with an automatic transmission.
Turn the engine off and remove the object from the vacuum line.
Press the vacuum line onto its fitting on the distributor.
