Setting Ignition Timing Video – Advance Auto Parts


Chad: I’m Chad Reynolds David: And I’m David Freiberger. Chad: And on this video commit points are
not understand and set ignition timing on your engine. David: Before we show you how to set ignition
timing, you’ve got to understand what it is. Go back to the stroke
cycle of engine, compression, power and exhaust. And on the
power stroke, the spark plug fires and starts an explosion the
crams the piston down the cylinder and makes horsepower for
you. In truth, that spark happens a few degrees before the power
stroke at the end of the compression stroke. In other words,
right as the piston is coming up for compression, just before
it reaches top dead center, or TDC, the spark plug fires. That
distance before top dead center is what is known as ignition timing.
Ignition timing is typically read from a market that’s
on the harmonic balancer on the front of the engine, and the
zero point represents top dead center from the number
one cylinder in between the compression and power stroke.
This is zero mark will have been set by the factory on your engine,
or perhaps buy the machine shop that built it for you, but it’s
critical that that mark be said exactly top dead center on number
one. Now, I’m going to rotate the engine here with
a breaker bar to simulate what happens here on the timing tape comes
he can see what we’re talking about. Right now we’re before top
dead center, and the piston is on its way up. So right here. So,
right here if I stop, the piston is now at 20 degrees before
top dead center, and it’s moving on its way up the cylinder.
There’s 10 degrees before, five degrees before, and then I went
a little bit after, but that’s a roughly zero or right at top
dead center. Now, the piston is moving back down the hole, and now
it’s 10 degrees after top dead center. So as the engine rotates,
the piston comes up, stops for just a millisecond at
top dead center, and starts to move its way back down. Now that’s
the mark that we use to determine ignition timing. David: Now that you understand how the MSD
timing tape on the damper relates to the piston position in the engine,
you can understand that I have it right now at 12 degrees before
top dead center. That would be a typical initial timing adjustment
for a small block Chevy. Now, if I were to advance the
timing, that would mean making the number larger or more degrees
before top dead center. If I were to retard the timing, it
would mean moving it to less degrees, or a smaller number before
top dead center. So if you’re at 12 and you change it to 20, that’s
advancing timing. If you’re at 12 and you change it
to zero, that’s retarding the time. Now that we’ve described
what an ignition timing number means as far as crankshaft degrees
and the position of the piston in the cylinder, I
can tell you about the three aspects of ignition timing that you
need to know. The first of those is initial timing setting,
also known as the idle timing. That is the total ignition advance
set when the engine is idle. The next aspect is total ignition
timing or the greatest amount of advance that the engine
achieves at higher rpm. The third thing you need to know is ignition
timing curve, which is the rate at which the ignition timing
advances between the initial timing and the total timing. Now,
I’ve explained that there is an ignition timing curve between
initial timing, which is a lower number, and total timing
which is a higher number, but you might ask; why does ignition
timing need to advance as engine speed increases. Think of
it this way. We always want peak combustion pressure to happen
at the same point in the piston travel, say about 10 degrees
after top dead center on the power stroke. Let’s assume that there
is a fixed amount of time between when the sparkplug fires and
when the point of peak pressure occurs. So if that is a fixed
amount of time, you can see that as engine rpm or speed increases,
you need to ignite the spark sooner so peak combustion
happens at the same place regardless of engine speed. Chad: Now that you’ve got the theory down,
it’s time to hook up your timing light and check your initial timing. Here’s
how you do that. If you’ve got an MSD timing might or anybody
else’s, what you’re going to do is hook up your cable to power
and ground on your battery. This does not plug into the wall,
and then also take this pickup and hook it to your number one
spark plug wire. You’ll note that on some timing lights, there’s
an arrow that points in the direction of the spark, in other
words that arrow needs to point at the spark plug. You hook
this up to the number one spark plug wire. Every time the number
one spark plug fires, this sensor picks it up, creates a strobe
effect with this light so that you can read the timing mark on the
balancer. David: Here’s what you’re seeing through the
timing lights. You can see the initial timing setting is about 12
degrees right here. Now watch as engine rpm increases, you can
see the timing advances up to about 33 or 4 degrees. It will
start to jump around up there and that’s not actually what
the engine’s doing, that’s a result of our camera shutter speed.
But anyway, you get the point that as engine rpm increases, so
does timing advance. We just showed you how to read timing, and
now I’m going to tell you how to adjust it. First thing you need
to do is loosen the bolts that hold your distributor hold down
clamps so that you can rotate the distributor housing. Now, on
this Chevy, where the rotor returns clockwise, you would advance
the timing by turning the distributor counterclockwise,
or retard the timing by turning it clockwise. Here’s how that looks
on the timing tape. Now watch as, here’s our base timing,
this is going to be advancing that, here it comes back to where
it was, and now I’m retarding it. Now we’re going to look at setting
the total ignition curve on this engine, which is defined
again by the point between initial timing and total timing,
and how fast it gets there. Chad: The most important thing for maximum
performance is total timing, and on a typical small block Chevrolet like this,
you’re aiming for between 34 and 36 degrees. So what we’re going
to do season a time in my, fire the engine and rev it up
to somewhere between 3500 and 4000 RPM wherever our timing quits
increasing. When we get it to where it stops adding advance with
the distributor, I’ll adjust the distributor so that our timing
reads at 35 degrees, and then we’re going to lock down
the distributor. David: After we locked in our total timing
at 35, we checked our timing at idle, our initial timing setting.
We found out that it was 19 degrees. What that means is that this
distributor has 16 crankshaft degrees of total timing in it between
19 and 35. Now, honestly financial at a rowdy cam, that’s
probably about right. A tamer engine can use 12, 15 degrees, something
like that. The thing about the MSD distributor is that all
of that is easily adjustable, and I’ll show you about that right
now. Now we get into the guts of the MSD distributor so that
we can change our timing curve. Every Pro-Billet kit comes with
a variety of springs and a variety of stock bushings so
that you can adjust the total advanced curve in the distributor
according to the charts on the side of the box. You can change
the total range of timing within the distributor and the rate
at which it goes from initial to total. The lighter the springs
that you put on these advanced weights, the faster the curve; the
heavier the springs, the slower the curve. In addition to changing the rate of the curve
with the springs, you can change the overall sweep of timing
inside the distributor with these little bushings, and
you have to get an 11/32 wrench in here right underneath that
advanced weight it and take off a little not to get to that bushing.
And finally, there’s the one thing that we can’t really
tell you here, which is exactly what the right advanced curve is
for your car. That’s going to be a matter of trial and error. In
general, if your car has more compression, a rowdier cam, if it’s
lighter, if it has lower rear gears, a looser converter, that
can generally accept a faster curve. A car that’s going to need
a slower curve would have lower compression, have a smaller cam,
it would be heavier, have higher gears as a tighter converter.
That’s sort of a general trend the way things are going to
go, but you can mess with it. It’s pretty easy to change the springs
on that Probilit distributor, but you can make it even easier
on yourself and not have to deal with an centrifugal local advanced
mechanism if you pick up one of those MSD digital e-curve distributors,
at which point all you have to do is change a couple
of switches with a little tiny screwdriver and you can set your
entire ignition curve electronically. Chad: Don’t forget that all the information
you need is right here on the side of your distributor box. It tells you
what springs and what bushings will give you what combination of
rate and total timing sweep.