Points and Magnetic Pickup Distributors If the rotor phasing is off on your distributor, there are several options to adjust the phasing. The points plate or pickup needs to be moved or the cap can be repositioned. In most cases these are major modifications which is why MSD checks the phasing of every one of our Pro Billet Distributors during the assembly process.
Crank Trigger Applications: In crank trigger applications, the distributor does not control the ignition timing so adjusting rotor phasing is easy. Simply rotate the distributor housing until the rotor tip is in the correct position.
Phasing and Electronic Timing Controls: When setting the phasing, you also need to take into consideration any timing controls or retard controls. If you are advancing or retarding the timing electronically, you are affecting rotor phasing. In most cases, the timing change will not be enough to affect the phasing, but there are applications to watch. One such application is with multiple stage nitrous systems and retard steps. High performance, nitrous engines undergo extreme increases in cylinder pressures which is why timing is generally removed with each stage of nitrous. If your application pulls out a total of 16 degrees, it is important to take this into consideration when setting the phasing. If you remove 16 degrees of timing, the rotor tip is going to be past the cap terminal when it fires. On engines with extreme cylinder pressures and high rpm, this could easily cause a misfire or spark scatter which could result in severe engine damage. It is recommended to divide the total amount of retard and set the phasing at that point.
For example, on an engine that pulls out 16 degrees of timing, you should set the rotor phasing when the timing is 8 degrees retarded. (Figure 5) This way with no retards the phasing will be 8 derees advanced, or just in front of the distributor cap terminal and when the full amount of retard is activated, the phasing will be just after the terminal (clockwise distibutors). Whenever checking the rotor phasing with an electronic timing control, it is important to check it with the retard activated and not activated.