Rotor Phasing For Motorcraft Distributors
Used in Ford & Jeep Vehicles From 1978 to 1990

This Page Will Instruct You How To Get Your Distributor Firing The Correct Plug Terminal At The Correct Time.

Rotor Phasing

First Off,
You want to cut a good sized hole in an old distributor cap, between the coil wire terminal and the #1 plug wire terminal.
In these pictures you can see the rotor with the alignment stripe already painted on it.

You want to use 'White Out' or a non electrical conducting paint, and paint a stripe on the nose of the rotor so you know where the middle of the rotor is.
Here is a picture of the rotor without the cap.

Disconnect the vacuum advance line from the distributor. Plug the line (golf 'T' works great).

Your test cap and rotor should look something like this when lined up with the plug wire you have chosen...

Start the engine and shine a timing light (non-dial back light if possible) in the test cap hole.
Mark the position of the rotor nose on the cap at idle with the vacuum advance unhooked.
This will be the 'NO ADVANCE' position.

Rev the engine up to about 3,500 rpm and mark the rotor position.
When you have made the mark, Let the RPM drop to idle.
This will be the 'FULL ADVANCE' position.

Attach a clean vacuum line to the vacuum advance, and draw full vacuum against the advance diaphragm.
(You can do this by mouth or with a vacuum pump.)

Rev the engine up to 3,500 again with the full advance on the vacuum side.
Mark the rotor position.
Mark this point also if it's more advanced than with the vacuum advance plugged.
You are looking for the most advanced position, mark it.

Now, the idea is to have your full advance and full retard marks the same distance away from the centerline of the #1 Plug wire terminal as possible.
If they look about like the image below, you are fine and no further adjustment is needed.

Just put your good distributor cap back on, put a touch of dielectric grease on the rotor nose, where the coil wire contact touches the rotor, and in the groove around the bottom side of the cap, and button things up!

If they look something like the one below, you will need to adjust the rotor phasing by moving the relitave mounting position of the reluctor.
Bear with me, it's a lot easier than it sounds...

How you achieve this is to move the Reluctor around the rotor shaft it's mounted to.
(The Reluctor is the little 'Wagon Wheel' or 'Spoke' Looking thing that has arms that line up with the magnetic trigger.)

It's held in place only by the friction of one little roll pin, so it can be pried straight up and off the center shaft with two screw drivers. (Be Very Careful!)

I recommend you use a gear puller, or an actual reluctor puller, but if you only plan to take it off once or twice, the expense of a specialty tool isn't worth it.
Just make sure you pry on the base circle of the reluctor and not the 'Spokes' or 'Arms'...

If you bend one these even a tiny amount, the reluctor is shot!
So pry on the base circle, closest to the shaft.
That is where the Reluctor is strongest.


This article is written for Motorcraft distributors, and both Ford & Jeep used Motorcraft distributors.
The differance is, some of the Jeep distributors were turned in the oppisite direction of the average Ford distributor, and that will complicate things a little.

Figure out if you need to move the rotor for proper phasing.
Some are just a little off and won't need to be moved.

Some are nearly a full plug terminal off and MUST be moved for proper operation.

If you do...
First & Formost, Figure Out If You Need To Move To The 'Advance' Side Or The 'Retard' Side.
'Advance' direction will always be against the pull of the vacuum advance.
'Retard' direction will always be with the pull of the vacuum advance.

1.Figure out how much in degrees of rotation, and what direction.
Remember, you want to figure the Reluctor as a stationary, and figure what direction the ROTOR needs to move, and how may degrees the rotor needs to move...

2.Mark the reluctor at the roll pin groove you are using.
(may reluctors have two or three already cut, so mark the one you are using, and remember, you may be able to use one of the others unless it is directly across from the one you have marked...)

3.Remove the reluctor.
Remember to pry up on the base circle, NOT THE 'ARMS' OR 'SPOKES'!

4.Figure the reluctor as a stationary piece, and figure what direction the rotor needs to go, and how much in degrees.
'Advance' direction will always be against the pull of the vacuum advance.
'Retard' direction will always be with the pull of the vacuum advance.

5.Transfer that to the Reluctor and mark the Reluctor for the new groove.

6.Move the roll pin groove on the inside of the reluctor accordingly.
Square file, triangular file, ect, but don't cut too deep!

7.Assemble and retest.

8.Repeat until you get the correct phasing.
Very common to go the wrong way the first time, so don't feel like you made a major mistake.
(I still do it on CCW distributors all the time...)

You have to "Move The Groove" in the Reluctor.

I do this by using an old distributor rotor/ reluctor shaft as a drill guide.
Drop the reluctor on the shaft, line up the new mark on the rotor with the roll pin slot, and drill away using the shaft slot as a drill guide.

If you don't have an old distributor shaft lying around...
You can also use a 'Dremmel' tool, a triangular file or even a keyhole hacksaw.
I have started using an abrasive edge jig saw blade in a manual handle (Gerber Multi-Tool) for doing field work.
It's slow, but the abrasive leaves a nice, clean, rounded groove.

This is only a 'Detent' groove! Don't cut too deep or too wide or the roll pin won't stay in place!

What To Do If You Screw Up...
Saving you from yourself!

1.Finding out you got the groove on the wrong side... Real common until you get the hang of this...
Just cut another one on the other side of the original slot, or cut on the opposite side of another trigger 'Arm'. You get at least six tries here...
2.Finding out you under or over estimated the rotation needed, and the slots will be too close together when you correct.
Just move to another 'Arm' or 'Spoke' and start over.

I often do one 'Spoke' a few degrees to the right, the next one a few degrees more to the right, the next one a few degrees more...

The do the other side the other way, a few degrees to the left, the next a few more degrees, ect.
That way I don't have to grind in the field, I have a Reluctor in 'Stock' that will work reasonably well on all engines...

3.Cut the groove too deep to hold the roll pin...
Line up on another 'Arm' or 'Spoke' and start over,
Don't cut so deep this time!
The Reluctor 'Arms' are not proprietary, so as long as they are spaced properly around the base circle (IE: Don't bend them!), you can start and line up on any of them...

4. he reluctor is available separately, and under $5 normally if you screw up too badly while getting the hang of this. Not a bad idea to have an extra on hand before you start.
If you don't need it, you can always return it....