Mallory Ignition Mallory ACTIVE FUEL INJECTION/TACH ADAPTER 29074 - Manual

ACTIVE FUEL INJECTION/TACH ADAPTER
PART NO. 29074
Before electronic ignitions were common
(and even after they were, in some cases),
tachometer designs were geared toward the
existing point-type ignition systems. This meant
that a parallel-connection tachometer (one that
was triggered from the coil ‘-‘ terminal) usually
required a relatively high voltage (50-100v) to
trigger properly. The other type of tach
commonly used was the “series” tach, which
was triggered by the current pulse in the ignition
supply line whenever the points closed.
When aftermarket electronic ignitions started
becoming more popular, there arose a need for
some way to trigger these tachometers, most of
which were OEM designs. In addition, more cars
were using electronic fuel injection systems, and
many of these systems required a HV pulse on
the coil ‘-‘ terminal to tell them that the ignition
was working before they would trigger the
injectors.
The first “tach/FI” adapters were just a coil of
wire that simulated a weak coil primary. Our
version is the 29074. When connected between
the points trigger lead and the ignition power
wire, they would make a HV pulse on the trigger
wire when the ignition was triggered. In addition,
they drew a couple of amps through the ignition
wire, and this was generally enough to trigger a
series tach that was in the circuit.
FORM 1139 (REV B)
As distributors with magnetic pickups became
more popular triggering sources, the 29074 style
adapter wouldn’t work, because the point lead
was no longer available as a trigger lead. In this
case, a more complex adapter was designed
(the 29078). This unit gets it’s trigger information
from the “Tach” terminal of the ignition box and
generates a HV pulse for parallel tachometers or
FI systems, and it also pulls a couple of amps
on the ignition line to trigger series tachometers.
If you are using the points trigger lead (in other
words, points, OEM electronic, UniLite,
50-series, etc.) for the ignition, then a 29074 is
the appropriate adapter. It should work with both
parallel and series tachometers.
The basic wiring diagram is located on the
reverse side of this sheet.
INSTALLATION INSTRUCTIONS
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