Technical information

AUTOTRONIC CONTROLS CORPORATION • 1490 HENRY BRENNAN, EL PASO, TEXAS 79936 • [phone] • FAX [phone]
www.msdignition.com email: [e-mail]
14
DISTRIBUTOR SETUP TIPS
If the distributor has vacuum advance, leave it connected
and check the phasing at your average driving rpm
and at a lower rpm. At high rpm, note the rotor position
and mark it on the cap terminal, then check it at low
rpm and again mark the rotor position. The phasing
should be set in the middle.
If the phasing is not correct on a points or electronic
triggered distributor, the trigger device must be moved
until rotor/terminal alignment is achieved. (MSD mag-
netic pickup distributors are set at the factory and should
not require adjusting.) If your application does require
adjustment MSD offers a Cap-A-Dapt with an adjustable
rotor, PN 8420. This compensates for the phasing with-
out having to move the trigger mechanism.
If you are using a Crank Trigger system to trigger the
ignition, rotor phasing is easy to set by adjusting the
housing of the distributor.
For applications that advance or retard the timing
electronically, rotor phasing must be taken into
consideration. If a multiple stage nitrous engine removes
16° of timing at top end, the rotor tip will be past the
cap terminal when the spark is triggered.
Rotor Phasing
Rotor phasing is the alignment between the rotor
tip and the distributor cap terminal when the spark oc-
curs. If the rotor tip is not aligned with the post when
the spark occurs, the spark may find another path to
ground resulting in scattered timing or a missfire. On
engines with extreme cylinder pressures such as ni-
trous or superchargers the rotor phasing becomes even
more important.
To check rotor phasing, you need an extra cap that
you can drill or cut a hole in to expose a terminal. It
may help to mark a reference center line on the rotor
tip and the terminal post with white correction fluid.
Connect a timing light to the wire of the exposed terminal.
With the engine running, the phasing can be observed.
It is correct when the center line reference marks are
aligned.