Quoting Kevin Pacheco <kevin50187@xxxxxxxxxxx>:
> Where are you supposed to set the mark to? theres a metal strip that
> has
> markings on it, but not sure where to set it.
> Im using 91 octain and the elevations is over 7,000
>
> Kevin Pacheco 71 IMP
>
This sheet metal piece has some markings on it. There is a zero in the middle,
and then if I recall 3 marks from each side, 5 degrees each. So, you have
reading resolution of 15 degrees befrore and 15 degrees after TDC.
One of the cables of the timing light goes around the plug wire of spark plug
of cylinder number 1 (I think that's on the driver side, the one up front, but
check to make sure). With engine idling, aim at the harmonic balancer, the
little disk of about 1 inch thick that's rotating under this sheet metal
piece. You will see a little horizontal groove on the harmonic balancer
flashing and appearing motionless. If the little line is below the zero mark,
that means you are before TDC (which is where you should be). Now, if you
loosen the distributor and rotate it a little, you will see this mark moving up
and down. When you rotate the distributor clockwise (the little vacuum advance
module is moving towards the front of the car) you are advancing and you will
notice the mark is dropping.
What is the optimum setting for your car? Keep on advancing till you hear the
engine pinging (on a fully warmed up engine). Dick B. suggests to test for
pinging at around 30 mph on D, by pushing the gas on a medium to light
acceleration. I do it differently. Since my cars are slightly modified, I
never hear pinging in that condition (unless the timing is way too advanced).
I do a WOT acceleration throughut the rpm range of the engine w/ 1st or 2nd gear
(from 2000 all the way to 4500, no reason to rev it further if you are trying
to detect knock). If you don't hear any knocking, advance some more,
regardless of what the timing light says (the more you advance, the higher the
performance and economy, and the lower the exhaust temperature). When you do
start hearing the familiar pinging sound, retard a hair (say one or two
degrees) and leave it there. Use the timing light to record this "optimum"
setting, so if you have to mess with the timing again, you won't have to go
through all that. Its possible that in the summer you may have to retard a
hair more. The hotte the engine, the more it tends to ping.
Beware: some real low compression ratio engines that have no carbon deposits
(I don't think the 71 is included, I think the 71 has close to 9 which is
almost healthy) may never knock, especially when premium gas is used. If you
use the above technique, you may end up advancing way too much, which will be
beyond optimum. One of the symptoms for this case may be hard starting.
D^2
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