IML - Vacuum and pinging

[MNTwin1@xxxxxxx]

In a message dated 8/19/02 1:53:19 PM Central Daylight Time, mailing-list-owner@xxxxxxxxxxxxxxxx writes:

The vacuum is supplied by an orifice just above the throttle butterfly, so
that at idle, there is no vacuum advance (the butterfly is not open
significantly), but as the throttle is opened, the orifice begins to see
more and more of the intake manifold vacuum, finally dropping off again as
the throttle approaches wide open, due to the loss of restriction between
the outside air and the intake manifold.

Thus, the vacuum advance has a strong effect at part throttle, advancing the
timing at part load, but this disappears as the load increases and the
vacuum falls toward zero.

This is a very timely topic for me.  I know this has been discussed before - Imperials and pinging.  My 68 Imperial is driving me nuts with its ping, ping, ping!  Help!

This year I installed new Autolite 85 plugs as recommended by the IML.  It did help as the old Split Fires were not a good plug for this car.  The plug gap has been double checked, the points are new, set correctly, timing has been checked and verified to be on spec.  I have had my FSM out in the garage with me along with my timing light and my dwell meter.  All numbers for ignition setting fall within the range in the manuals.  I run 92 octane gas in the car.

I notice that I get pinging when driving at moderate speeds - say 45-55 mph - and then accelerate slowly.  The guy will ping like crazy.  If I drive at the same moderate speed and hit the pedal harder so that I accelerate like a race car there is no ping.

So I ask the expert panel... what is the problem with my Imperial?? It seems to fit Dick's explanation.  If he is correct,  what is my solution?

I appreciate the help!

Dale
68 Crown Coupe - Forest green and pinging!