Ignition timing and fuel/air mixture are interrelated
parameters. Since excessive
ignition timing advance and excessively lean fuel/air mixture
will both contribute
to pinging problems, adjusting these parameters for optimum
performance is an
iterative, trial-and-error process.
You might advance ignition timing a little, then enrich the
fuel/air mixture, then
advance ignition timing a little more, etc.
Understanding ignition timing
Ignition timing refers to the timing of the spark plug firing,
relative to the
crankshaft position. Ignition timing is measured on the spark
plug of the #1
There are two elements of ignition timing:
Base timing, and
Ignition base timing is what you measure with a timing light
and adjust by rotating
the distributor body.
Timing advance is the change in ignition timing (from the base
timing) produced by
a timing advance mechanism. The term “advance curve” refers to
the rate at which
the timing advance changes.
Most Ford distributors built since 1968 have both mechanical
advance and vacuum
The mechanical advance system consists of weighted cams and
provide ignition timing advance as engine speed increases.
causes the weighted cams to move and advance the timing, so
is sometimes referred to as centrifugal advance.
The vacuum advance system consists of a vacuum motor
connected to the base
plate of the distributor. It provides ignition timing
advance in response
to a vacuum signal. The source of the vacuum advance signal
is usually the
carburetor’s “spark port.”
Ignition base timing and vacuum advance can be easily adjusted
without removing or
disassembling the distributor. Adjusting the mechanical advance
requires at least
partial disassembly of the distributor.
Tools for adjusting ignition timing
Adjusting ignition timing requires just a few special tools:
I recommend a decent timing light with an inductive pickup and a
bulb. The xenon bulb produces enough light that you can see the
daylight, which makes it easier to work on your engine. You
don’t need a fancy
timing light with advance/delay adjustments.
You need a decent (reasonably accurate) vacuum gauge for tuning
vacuum advance and adjusting the idle speed.
You also need an accurate tachometer, ideally one that can show
down to 25 rpm or so. You’ll use the tachometer to adjust idle
speed and to
measure rpm when checking the ignition advance.
Adjusting ignition base timing
Use this procedure to adjust ignition base timing for maximum