Mallory Ignition А557 User Manual

FORM 1627

INSTALLATION INSTRUCTIONS

Mallory Distributor Model #A557

CAUTION: CAREFULLY READ INSTRUCTIONS BEFORE PROCEEDING. NOT LEGAL FOR USE OR SALE ON POLLUTION CONTROLLED VECHICLES

OVERVIEW

Mallory distributor Model A557 is intended for use with 1936-1969 Harley­Davidson® 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 modi­fications necessitate carburetor re-jetting. Carburetors are never cor­rectly 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 non­resistor 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 recom­mend 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 recom­mend the ACCEL 140408 coil. For dual fire use ACCEL part number 140407.

• Distributor clamp – A 1966-69 style distributor clamp (original or aftermar­ket) is required.

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 distribu­tor 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 approxi­mate 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 recom­mend 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

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Figure 1

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Figure 2

Modes” instruction below.

10. Install the top cover using the two supplied hex
head screws. We recommend using a drop of blue
threadlock to prevent the standoffs from vibrating
loose.

11. Route the wiring harness between the pushrod
tubes and the cylinders and up to the coil. Try to
keep the harness away from the hot cylinder fins.
Connect the wires as indicated in the attached
“single fire/dual fire” wiring diagrams (page 4-5)

12. The timing should now be close enough to start the
engine. If not, loosen the distributor clamp and turn
the distributor slightly in either direction until the
engine starts. Once the engine has warmed up, the
timing can be set with a timing light. Adjustment to
the timing can be made by loosening the distributor
clamp and rotating the entire distributor. If neces­sary, the entire distributor can be removed and
rotated one gear tooth to allow the wiring harness to
run between the pushrod tubes and cylinders. For
additional timing information see pages 3.

OPERATING MODES

A single 10 position rotary switch is used to select the
operating mode. Switch settings are as follows:

0 Street advance curves, dual fire, multi-spark dis­abled
1 Street advance curves, dual fire, multi-spark enabled
2 Street advance curves, single fire, multi-spark
disabled
3 Street advance curves, single fire, multi-spark
enabled
4 Race advance curves, dual fire, multi-spark disabled
5 Race advance curves, dual fire, multi-spark enabled
6 Race advance curves, single fire, multi-spark dis­abled
7 Race advance curves, single fire, multi-spark
enabled
8 Not used
9 Not used

Figure 3

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The engine will not run if the mode switch setting
does not match the wiring hookup (i.e. you cannot
select single fire mode with a dual fire coil hookup).
Advance curve families are shown in Figures 6 and

7. Use the street advance curves (mode switch settings

0-3) for stock or mildly modified engines. Use the race
advance curves (mode switch settings 4-7) for high
compression engines.
We recommend that you enable multi-spark. When
multi-spark is enabled, a continuous series of sparks
is fired from the advanced timing point until TDC. Most
air-cooled engines require relatively cold spark plugs
to prevent detonation under high load. Multi-spark
reduces the consequent tendency for plug fouling at
idle.

CAUTION: Engine damage from
excessive timing advance may
result if the purple/white VOES wire
is inadvertently shorted to ground.

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RECOMMENDED TIMING SETTINGS

Street and race advance curve families are shown in Figures 6 and

7. Each family has minimum and maximum curves. The advance slope
switch allows you to run an advance curve in between these minimum and
maximum curves. Advance slope switch setting zero corresponds to the
minimum advance curve. Switch setting 9 corresponds to the maximum
advance curve. Higher switch settings result in a more aggressive curve.
Tuning a particular engine setup always requires some trial and error
experimentation, but maximum power is usually obtained by using the high­est advance setting possible without audible spark knock. Some recom­mended starting points are given below:
For stock engines run on normal pump gas (87-89 octane), use the street
advance curves and advance slope setting 5.
For stock or mildly modified engines run on 92 or higher octane gas, use
the street advance curves and advance slope setting 7.
For high compression engines, use the race advance curves and
advance slope setting 2.
You can adjust the initial timing by rotating the ACCEL module relative to
the gear housing (clockwise rotation increases initial timing).
If you experience spark knock only at low RPM, you can try reducing the
initial timing while maintaining an aggressive advance slope for maximum
power at high RPM by increasing the advance slope switch setting. If spark
knock is a problem at high RPM, decrease the advance slope switch set­ting.
Note that the wide-open throttle (WOT) curves are active unless the
VOES input is grounded. During idle and cruise, the VOES input is grounded
(green VOES LED illuminated) and the low manifold pressure (MAP) curves
are active.

RPM LIMITER SETTING

You can set the RPM limit from 3,000 to 9,900 RPM in 100 RPM incre­ments by means of two rotary switches. The RPM limit is X100 switch set­ting (i.e. 57 = 5,700 RPM). Inadvertent settings below 3,000 RPM are ignored
and result in a 3,000 RPM limit.
The Model 35496 uses a newly developed RPM limiting algorithm that
has been highly optimized for odd firing V twin engines. When the engine is
held against the RPM limit, cylinder firing is always paired. This eliminates
a torque couple and results in very smooth operation compared to random
or sequence type RPM limiters.
Set a safe RPM limit that is appropriate for your engine. Most Evolution®
engines with OE valvetrain components should not be run over 5,700 RPM.

STATIC TIMING PROCEDURE

1. Timing marks are located on the flywheel and may be viewed by
unscrewing the inspection hole plug. Most engines will have both TDC
and advance timing marks for the front cylinder as shown on pg 7s. If you
are not sure, refer to your shop manual. You can also identify the TDC
mark by removing the spark plugs and rotating the crankshaft (turn rear
wheel in high gear) until the front piston comes up on TDC.

2. For static timing, you must rotate the crankshaft so that the front piston
is at TDC on the compression stroke. Remove spark plugs and rotate
crankshaft. If you place your thumb over the spark plug hole, you will feel
pressure as the piston comes up on the compression stroke. Continue
rotating the crankshaft until the TDC mark is precisely centered in the
inspection hole.

3. Ground the spark plug cables to avoid a shock hazard. You can use small
jumper wires with alligator clips for this purpose.

4. Turn on the ignition switch. The red LED is used as a timing indicator. Note
that the LED does not immediately illuminate when power is first turned
on. Rotate the ignition unit back and forth until the red LED illuminates.
Then slowly rotate the unit clockwise until the LED goes out. Note that
the LED goes out at TDC.

5. Tighten the standoffs to secure the unit. Turn off the ignition switch and
reinstall the spark plugs.

2. The precise timing procedure is based on using the 35° BTDC timing mark
and race maximum advance curve with VOES grounded that reaches 35°
BTDC around 2,000 RPM (refer to Figure 7). To use this procedure, you
must have a VOES switch connected. If a VOES switch is not used, you
must ground the purple/white wire while setting the timing.

3. Set mode switch to 4 for dual fire or 6 for single fire. Set advance slope
switch to 9. Connect the timing light pickup to the front cylinder spark
plug cable. Loosen standoffs securing the ignition unit. Run the engine
at a steady speed just over 2,000 RPM. Rotate the ignition to center the
35° BTDC timing mark in the inspection hole. Tighten standoffs and verify
that the timing has not changed. When done, change mode and advance
slope switches back to desired values.

GENERAL RECOMMENDATIONS

Coil primary resistance must not be less than 3 ohms. Most OE style dual
fire and aftermarket single fire coils meet this requirement. Coils for the new
Twin Cam engine have low primary resistance and are not compatible.
Due to the short lengths involved on motorcycle applications, energy losses
in spark plug wires are insignificant. OE carbon core suppression cables
will deteriorate after several years. For a more durable replacement, we
suggest spiral core spark plug cables.
The ACCEL module is compatible with all modern “ground sensing”
type tachometers including H-D® OE and Autometer units. The red status
LED is internally connected to the tachometer output. If the red status LED
blinks, the tachometer output should be functional. Some early tachometers
require a high voltage trigger pulse. In this case, you will require a commer­cially available tachometer adapter.

VOES CONSIDERATIONS

The vacuum switch (VOES) provides the vacuum advance required by
all street driven engines. Additional advance under low manifold pressure
conditions improves idle stability and fuel economy. Most 1980 and later
motorcycles are equipped with a OE VOES. Without vacuum advance at idle
and part throttle, thermodynamic efficiency is reduced and engine tempera­tures increase significantly.
The VOES is normally open. At low manifold pressure (or manifold
vacuum greater than about 5 inch-Hg), the VOES grounds the purple/white
wire and causes the ACCEL module to generate additional timing advance.
The green VOES LED illuminates whenever the VOES input is active (timing
advanced).
The use of a VOES is required for proper operation of the ACCEL module.
If your motorcycle did not include an OE VOES, you can use H-D® VOES P/N
26566-91 for stock or mildly modified engines.

TROUBLESHOOTING FLOWCHART

Follow the troubleshooting flowchart shown on pg. 8. Experience has
shown that most units returned for warranty are OK and another problem,
such as a defective coil, is later identified.

PRECISE TIMING PROCEDURE

1. Use a standard timing light. Note that most dial-back type timing lights
will not work correctly with dual fire applications. If you have a dial-back
timing light, set the dial-back to zero. Do not enable multi-spark while
setting timing.

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