Mallory Ignition Mallory DISTRIBUTOR А557 - Manual

MALLORY IGNITION www.mallory-ignition.com 1
Mallory Distributor Model #A557
FORM 1627
INSTALLATION INSTRUCTIONS
OVERVIEW
Mallory distributor Model A557 is intended for use with 1936-1969 Harley-
Davidson® Big Twin motorcycle engines. The Mallory A557 replaces the
original equipment (OE) points type distributor. The unit can be installed
without engine disassembly when stock cylinders and heads are used.
The Mallory A557 offers adjustable advance, adjustable RPM limit settings
in 100 RPM increments, and switch selectable single or dual fire modes.
Single fire mode improves starting, reduces the occurrence of backfiring at
low RPM, and improves power at high RPM. A red status LED flashes when
the engine reaches top dead center (TDC) and allows easy static timing.
The status LED also provides diagnostic information. A green VOES LED
illuminates when the VOES (vacuum switch) input is active.
AVOIDING HEAT RELATED FAILURES
Heat kills electronics. The Mallory A557 uses electronic devices rated for
operation at 105 deg. C (221 deg. F), the highest rating available. The unit
can tolerate somewhat higher temperatures, but exposure to temperatures
above 125 deg. C (257 deg. F) will greatly reduce life expectancy. We
sometimes see problematic applications where several module failures
have occurred. The failure mode is a classic thermal intermittent where the
module stops firing one cylinder when it gets hot. We have found that these
problematic applications share one or more of the following characteristics:
• VOES switch removed or non-functional. All street driven engines require
vacuum advance. Without vacuum advance at idle and part throttle,
thermodynamic efficiency is reduced and engine temperatures increase
significantly.
• Improper carburetor jetting resulting in lean air/fuel ratio (AFR). A lean
AFR will cause the engine to run very hot. All performance engine modi-
fications necessitate carburetor re-jetting. Carburetors are never cor-
rectly jetted out-of-the-box. The only practical means of correctly jetting
a carburetor is to test the motorcycle on a chassis dyno equipped with an
exhaust gas sniffer.
• Lack of an oil cooler on a 95 CID or larger engine.
• Exhaust pipe without heat shield in close proximity to the distributor.
• If any of the above applies to your application, the Mallory A557 may be
exposed to excessive temperatures resulting in reduced life expectancy.
Use an infrared thermometer to check the module temperature.
INCLUDED AND ADDITIONAL REQUIRED PARTS
All units include a parts bag with crimp terminals for coil and VOES hookup.
• Electrical System - A 12 volt electrical system is required. Check that the
charging system is properly regulated and not producing over 16 volts.
• Spark plugs – Resistor spark plugs must be used in place of the non-
resistor spark plugs that were original equipment.
• Ignition wire - Spiral core or carbon core wire must be used in place of the
solid core or copper core wire that was original equipment. We recom-
mend the ACCEL 300+ Race Wire.
• Coil(s) – A coil or coils with a total primary resistance of 2-4 ohms is
required. The stock 5 ohm coil is not compatible. For single fire we recom-
mend the ACCEL 140408 coil. For dual fire use ACCEL part number 140407.
• Distributor clamp – A 1966-69 style distributor clamp (original or aftermar-
ket) is required.
CAUTION: CAREFULLY READ INSTRUCTIONS BEFORE PROCEEDING. NOT LEGAL FOR USE OR SALE ON POLLUTION CONTROLLED VECHICLES
INSTALLATION
1. Turn off the ignition switch and disconnect the battery ground
cable before proceeding.
2. Rotate the engine until it is on the compression stroke on the
front cylinder. Continue to rotate the engine until the TDC
mark is visible through the timing hole. (see pg 7)
3. Remove the existing distributor if still in the engine.
4. Remove the two hex-head screws and the top cover from the
new Mallory A557 distributor. Remove the two hex standoffs
and remove the module and upper housing from the distribu-
tor base assembly. (Figure 1)
5. Install the distributor base assembly in the engine with the
screw holes and shutter wheel positioned as shown in figure
2. It may be necessary to pull the distributor out, turn the
shaft, and reinstall to get the shutter wheel at the approxi-
mate angle shown. The shutter wheel openings should be at
about the 11 o’clock and 7 o’clock positions. The screw holes
should be at the 9 o’clock and 3 o’clock positions.
6. Install the distributor clamp and snug the clamp bolt loosely
so that the distributor can still be rotated.
7. Reinstall the upper housing and module assembly onto the
distributor base assembly as shown in figure 1. Note: the
upper housing will only install one way due to the locating
screw. Rotate the base assembly slightly if necessary so that
the opening in the shutter wheel lines up with the slot in the
upper housing (figure 3).
8. Reinstall the two hex standoffs through the module and upper
housing and into the distributor base assembly. We recom-
mend using a drop of blue threadlock to prevent the standoffs
from vibrating loose. Tighten the distributor clamp.
9. Set rotary switches according to the separate “Operating Figure 1