There have been three different types of distributors used on Mustangs. From 1964 to 1967, the six-cylinder engines were equipped with Loadomatic vacuum advance units. During this same period, certain high-performance V8 engines used a centrifugal advance distributor, which is most readily identifiable by the absence of a vacuum control line. All engines from 1968 to the present, as well as those V8 engines prior to 1968 (other than the types with centrifugal advance distributors) have been equipped with dual advance distributors.Loadomatic Vacuum Advance
See Figure 1
Ignition timing changes are entirely satisfied by the action of the breaker plate. The position of the plate is controlled by a vacuum-actuated diaphragm working against the tension of two accurately calibrated breaker plate springs. The diaphragm moves the breaker plate counterclockwise to advance the spark. The springs tend to counteract this movement to return timing to a retarded position. Cam and rotor rotation are clockwise as viewed from the top.
A purely mechanical unit, this distributor contains two centrifugal weights which cause the cam to move ahead with respect to the distributor driveshaft. The rate of advance is controlled by two calibrated springs which act against the centrifugal force of the two weights. The unit is also equipped with a governor to regulate the amount of advance possible.
The dual advance distributor has two independently operated spark-timing control systems. A governor type and a vacuum type control are used on each distributor of standard production engines. Centrifugal weights cause the cam to advance or rotate ahead, relative to the distributor shaft.
The vacuum control mechanism operates through a spring-loaded diaphragm and movable breaker plate, about the same as the vacuum advance distributor.
Many post-1970 Ford engines are equipped with a distributor modulator system to reduce engine emissions. It consists of four major components: a speed sensor, a thermal switch, an electronic control amplifier, and a three-way solenoid valve.
REMOVAL & INSTALLATION
See Figures 2 through 8
- Unfasten and remove the distributor cap. Disconnect the primary wire at the coil and the vacuum control line(s) at the distributor.
- Scribe a mark on the distributor body, to show the position of the rotor, and another mark on the distributor body and the block to show the position of the distributor in the block. Do not disturb the engine until after you have completely reinstalled the distributor, as this will defeat the purpose of the marks that you have just made. The marks are for the purpose of eliminating the need to retime the engine upon completion of the distributor work.
- Remove the screw, lockwasher, and hold-down clamp. Pull the distributor out of the block.
- Line up the rotor slightly to the left of the mark that you made to indicate its position.
- Insert the distributor into the block, aligning the marks that you made on the distributor body and the block. Push the distributor firmly into the block. As it descends into the installed position, the rotor lines up with the mark that you made to indicate its position.
- Install, but do not tighten, the hold-down clamp, lockwasher, and screw.
- If the engine has not been disturbed, there should be no need for retiming. Install and fasten the distributor cap, connect the distributor primary wire at the coil, and connect the vacuum control line at the distributor. After checking your marks on the block and the distributor housing for precise alignment, tighten the screw which secures the distributor hold-down clamp.