Adjusting rotor phasing – MSD 84211 Rotor Phasing Kit for MSD Distributors Tech Bulletin User Manual

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• W W W . M S D P E R F O R M A N C E . C O M • ( 9 1 5 ) 8 5 7 - 5 2 0 0 • F A X ( 9 1 5 ) 8 5 7 - 3 3 4 4

© 2012 Autotronic Controls Corporation

FRM31025

Revised 02/12

Printed in U.S.A.

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 re-

positioned. 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 advanc-

ing 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 pres-

sures which is why timing is generally removed with each stage of nitrous. If your

applications pulls out a total of 16° it is important to take this into consideration

when setting the phasing. If you remove 16° 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 sever 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° of timing, you should set the ro-

tor phasing when the timing is 8° retarded (Figure 5). This way, with no retards

activated the phasing will be 8° 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 distributors). Whenever checking the rotor phasing

with an electronic timing control, it is important to check it with the retard activated

and not activated.

Cap-A-Dapts

If you have enough room to run a larger cap, you should take advantage of the real estate. A larger cap spaces the termi-

nals farther apart so there is less chance of crossfire or spark scatter occurring. MSD offers a Cap-A-Dapt Kit, PN 8445, that

replaces the points/socket style cap on most of our Pro-Billet Distributors.

If you want to adjust the rotor phasing and use an MSD Pro-Billet Distributor with a magnetic pickup, we offer a Cap-A-

Dapt with an adjustable rotor PN 8420. This rotor is two pieces and is made so the rotor tip position can be altered. A smaller

adjustable rotor is now available as PN 84211 for use in place of rotor PN 8467.

Preventative Maintenance

Taking a little time between races to inspect your ignition system will help prevent minor problems. Periodically check the

following:

Visually inspect the cap and rotor for wear of the cap terminals and the rotor tip.

Look for traces of carbon tracks where spark scatter occurs.

Visually inspect the plug wires for burns or tears. Also, it is a good idea to periodically check the resistance of the wires.

MSD’s Spark Guard, PN 8804, is a dielectric grease that helps isolate the spark at the plug wire terminal and cap

connection.

Adjusting Rotor Phasing

Adjusting Rotor Phasing

Vacuum Advance: Vacuum advance affects rotor phasing so it should be checked

with the vacuum disconnected and connected. On a distributor that turns clockwise,

the rotor tip should be at the right or just after the terminal when the spark occurs

with the vacuum disconnected and plugged. With the advance connected and the

engine at a steady speed off idle, the rotor tip should be just to the left or before

the terminal (Figure 4).

Note: On distributors that turn counterclockwise, these positions will be opposite.

Figure 4 - Distributors with vacuum ad-
vance need to be checked with the vacuum
connected and disconnected.

Figure 5 - When using a timing retard,
compensate the rotor phasing.

frm31025_tb_rotor_phasing.indd 2

2/13/2012 1:56:55 PM

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