Mallory Ignition Mallory HYFIRE VII Series Electronic Ignition Controls 667C - Manual (Page 9)

HYFIRE ® VIIC AND VIIS
IGNITION SYSTEMS
Part One: Start Retard
The Mallory HYFIRE ® VIIC AND VIIS Ignition Systems both have a built-in start retard feature. This retard is
20 degrees at 100 RPM, and decreases to 0 degrees at 500 RPM. This is a very useful feature which
eases the load on the starter motor when used with vehicles that have crank triggered ignition systems or
distributors with locked advances and 30 or more degrees of timing. However, there are applications
where the start retard is either not needed or not wanted. For example, motors with radical camshaft
profiles, large carbs and timing in the 15 to 25 degree BTDC range (Pro Mod motors, for example) may
experience lean-mixture backfiring during startup if the retard feature is active, especially if the tempera-
ture is colder than usual.
Current production versions of the HYFIRE ® VIIC AND VIIS have a yellow wire loop which comes out of the
back of the ignition box. Cutting this loop eliminates the start retard. Earlier versions of the ignition don’t
have this feature, but the start retard can still be shut off. You must either send your ignition in to our service
department for modification, or, if you are attending an NHRA National event, you can bring your ignition to
our race support trailer and have it modified.
TECHNICAL BULLETIN
®
CUT YELLOW WIRE LOOP TO
ELIMINATE START RETARD
AFTER CUTTING YELLOW WIRE,
USE SHRINK TUBING TO INSULATE
EXPOSED ENDS
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