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nice job BL
----- Original Message -----
Sent: Friday, April 30, 2004 5:47
PM
Subject: Re: [Chevelle-list] timing
question (yes, another one...)
I am trying to understand the
whole concept of timing
in general
There are basically two
types of timing on motors--1.Cam timing, which is the relationship between the
cam lobes' opening and closing points and the crankshaft position. This
is set when the motor is built, and cannot be changed without disassembly of
the engine (usually) and, 2. Ignition timing, which is when the coil fires the
spark to ignite the fuel in the cylinder. This is adjusted by
twisting the distributor. The timing is measured by the marks on
the crankshaft pulley in relation to the marks on the timing tab that is
mounted on the timing chain cover on the driver's side of the motor.
When the coil fires, it sends current down the spark plug wire that jumps the
plug gap, creating a spark that burns the fuel. Since it takes a certain
amount of time for the fuel to burn, we need to send the spark down
before the piston reaches the top of it's stroke. However, if the
spark is sent too soon (too far advanced), the piston is working against the
pressure of the combustion and that causes a knocking sound and some loss of
power.
I have a timing light but
am not
entirely sure of where to hook it up on my Edelbrock
Performer
600 carb.
You don't hook a timing light to the carb--there are
different types of lights, but usually you will hook one wire to battery
positive, the other to battery negative, and the sensor to #1 spark plug
wire. On a Chevy, #1 cylinder is on the driver's side front. When
it's hooked up, the light will flash when the coil fires the #1 spark
plug. Before you use the light you will need to mark the crank pulley
where the line is scribed on it with a paint color that will contrast with the
pulley color. Also mark the timing tab with the same color paint at the
place where you want to set the timing. The timing tab is marked with a
0 in the middle. The marks that are above the 0 are Before Top Dead
Center (BTC), the marks below are After Top Dead Center (ATC). If you
want the timing a 10 deg BTC, paint the 10 deg mark on the tab. Usually
you will also need to take the vacuum hose off of the vacuum advance can on
the distributor and plug the hose with a golf tee or a screw. Start the
motor, and see where the marks are. If you marked 10 deg, the mark on
the crank pulley and the timing tab should line up. If the mark on the
crank is above the mark on the tab, the timing is advanced; loosen the
distributor hold down bolt and turn the distributor clockwise until the marks
line up. If the pulley mark is below the tab mark, the timing is
retarded and you'll need to turn the distributor counter clockwise to adjust
it.
Can I just turn the
distributor
counter-clockwise an 1/8" or so and see if that
helps?
Yep, but that will advance the timing, and that's not
the way you need to go to stop pinging. Turning it clockwise will retard
the timing.
Also when retarding the
timing, do I just loosen the
bolt and turn the distributor
slightly?
Yep, retarding or advancing.
Or do I have
to lift it
out of its existing position with the cam
gear and drop it back in?
Nope.
I don't know why, but
the
timing thing has always been a confusing topic to me.
I
hope I didn't confuse you even more. :-))
BL
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