Your car is acting correctly, but your timing is a little too advanced for
the condition of your combustion chambers (deposit build up). You need to
retard your initial timing about 5 degrees and I'm confident your problem
will disappear, or at least get much better. The optimum setting for timing
is when you just barely hear pinging at part throttle around 30 MPH, with
the car fully warmed up and the gas you plan to use. Adjust the timing by
ear to that point, and you will be very close to optimum for this cars
condition.
Dick Benjamin
----- Original Message -----
From: <>
To: <mailing-list@xxxxxxxxxxxxxxxx>
Sent: Monday, August 19, 2002 5:23 PM
Subject: Re: IML: IML - Vacuum and pinging
> 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!
>
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