Precision Turbo and Engine BigStuff3 GEN3 Powertrain Controller Ignition Setup Tutorial - Manual (Page 22)

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Using the Degreed Dampener or a Dampener with Timing Tape on it, instead of a degree wheel
Make sure that the pointer is solidly mounted so that it will not move and that you can see the numbers
on the radial face of the dampener.
TDC Procedure
Very slowly and carefully (via a breaker bar on the crankshaft bolt) rotate the crankshaft until the
piston lightly touches the piston stop. Write down the number the pointer is indicating on the degree
wheel. Rotate the crankshaft in the opposite direction again until the piston lightly touches the piston
stop. Again, write down the number the pointer is indicating on the degree wheel. TDC will be
exactly in between the two numbers that were recorded. Remove the piston stop and rotate the engine
to the number on the degree wheel now determined to be TDC. A new zero point mark needs to be
made on the dampener.
Crane Cams offers positive stops (brass), in 12mm (Part number 99410-1) & 14mm (Part number
99412-1) sizes. GM also offers a piston stop (Part number 12364087). They are made to screw
directly into the cylinder head spark plug hole and are machined from brass to prevent piston damage.
They incorporate an air bleed hole to prevent compression build-up while turning the engine over. If
the cylinder heads are off the engine, Use the same process as outlined above, except use a dial
indicator instead of a piston stop.
Crank Trigger (wheel, and sensor assembly) Considerations
The number of magnets (or raised metal studs) the crank wheel should have is based on the number
cylinders the engine has as shown below:
4-Cylinder Engine Example
The typical firing order for a 4 cylinder, 4 stroke engine is 1-3-4-2. To complete a 4-stroke cycle, the
crankshaft rotates 720 degrees, or two turns. The camshaft (ignition distributor), rotates at half-speed
or 1 turn for every 360° of crank rotation. A four cylinder has 720/4 = 180 degrees between ignition
firings.
Engine Cylinders Number of Magnets in
Crank Wheel
Magnet Spacing on Crank
Wheel
8 4 90
o
6 3 120
o
4 2 180
o
Some crank trigger assemblies use a crank wheel, with steel studs protruding from the wheel. As the
crankshaft turns the steel studs pass by a stationary magnetic pickup, creating a sinusoidal wave,
which is used to trigger the ignition. The potential exists for the magnetic pickup to false trigger.
Other steel objects like bolts, debris and even vibrations can cause magnetic pickups to false trigger.
False triggers can cause a loss of power and potentially damage the engine.