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Mallory Ignition Mallory BILLET HEI DISTRIBUTORS 75_Series User Manual

Page 4

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MALLORY IGNITION

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ADJUSTING THE AMOUNT OF MECHANICAL
ADVANCE (IF NECESSARY)

The distributor mechanical (centrifugal) advance
mechanism is adjusted at the factory to limit the
mechanical advance to 24°. In most cases, this will
work fine. However, in some rare cases, it may be
beneficial to change the factory setting. The adjustment
range is zero to 28°. If the limit is changed, it may be
necessary to change the initial timing as well.

To access the mechanical advance, remove the
distributor cap, rotor, rotor flange bolt and rotor flange.
Remove the module. Using a small puller, remove the
reluctor. Do not lose the small pin that locates the
reluctor. Remove the two set screws. Lift out pickup
plate assembly (See Figure 4). See Page 7 for
instructions on adjusting the mechanical advance limit.

CHANGING THE MECHANICAL
ADVANCE RATE

The advance springs installed at the factory produce
an advance curve that starts at 1200 rpm and is all-in
by 3200 rpm. If a faster or slower advance curve is
required, a spring kit (PN 29014) can be purchased
from Mallory dealers.

REPLACING THE MALLORY MODULE WITH AN
OEM STYLE MODULE

While the use of stock/OEM type modules will reduce
the spark energy and eliminate the rev limiter, in an
emergency, an OEM style HEI module can be used.
Cut the wire harness off of another module and attach
as shown in the photo on Figure 5.

SETTING THE INITIAL TIMING

Connect a timing light to the engine. Do not connect
the vacuum advance at this time. Start the engine
and allow it to warm up a few minutes at idle. If the
engine will not start or idle smoothly, try rotating the
distributor (in either direction) to get the timing closer
to optimum. If the engine will not start, the firing
order may be incorrect, or the rotor may not be
aligned correctly. Consult a repair manual for more
information.

Check the initial timing with the timing light. The
engine must be at idle (under 1200 rpm). Set the
initial timing between 5° and 12° BTDC and tighten
the clamp.

With the vacuum advance line still disconnected
and plugged, take the vehicle for a test drive. Listen
carefully while under full throttle in high gear. If you
hear knocking or pinging, reduce the initial timing by
2 degrees at a time until you no longer hear the engine
pinging or knocking. If you do not hear pinging or
knocking, increase initial timing by 2 degrees at a time
until you hear it, then reduce timing by 2 degrees.
Initial timing should never be less than 0 degrees or
more than 16 degrees. If the engine seems to run best
outside this range, something else is wrong. Find the
problem before continuing.

ADJUSTING THE VACUUM ADVANCE

The vacuum chamber is adjusted at the factory to
produce 12° of additional advance at steady speeds.
This may be too much for some engines. Connect a
vacuum line from the vacuum chamber to a ported
vacuum source on the carburetor. Take the vehicle for
another test drive. Drive the vehicle at a steady speed
in high gear on a highway that is level or slightly
inclined. If surging or pinging is noticed, the amount
of vacuum advance must be reduced. Pull the vacuum
line off the vacuum chamber. Insert a 3/32" allen
wrench into the chamber nipple and turn the
adjustment screw counterclockwise two turns.
Reconnect the hose and take another test drive.
Reduce the vacuum advance further if necessary to
eliminate surging or pinging.

WARNING:
The wire from the ignition switch must not be a
resistor type wire or contain a ballast resistor. If
your car has a ballast resistor, remove it or put a
jumper wire across it. If your car uses a resistor
wire for the ignition (many pre-1975 vehicles do),
you must run a different wire to the distributor from
the ignition key (or fuse box) so that full battery
voltage reaches the distributor. The distributor

will operate with a ballast or resistor wire, but
performance will be greatly reduced. To determine
if your car has a resistor wire, check the voltage of
the wire at the coil with the engine running. If the
voltage is within 1.5 volts of the battery voltage,
the wire is not a resistor type. If the voltage is not
within 1.5 volts of battery voltage, you must run a
new wire to the distributor.