Setting the Timing

• Make sure the truck is warmed up to normal operating temperature
• Locate the set timing connector plug
  • On my '92 Yukon it is a tan wire with a black stripe with a plastic connector behind the plastic junction box cover mounted (pic) on the passenager side of the firewall.
  • On some vehicles it may be under the dash perhaps behind the glovebox
  • Disconnect the plug
• Connect the timing light to the battery and spark plug wire #1

• Loosen the distributor hold down bolt
• Start the truck. The timing will be different with the set timing connector disconnected so it will sound different
• Move distributor until timing is set where you want it
  • Counter-clockwise to advance
  • Clockwise to retard
  • Start at 0 degrees before top dead center (BTDC)
• Tighten the distributor hold down bolt
• Check the timing again to make sure it didn't change when you tightened down the distributor
• Shut off the truck and reconnect the plug

  Nice diagram of the ignition system:
  

  What the timing tab supposedly looks like (mine is different)
  

  Last updated Apr 15, 2018
  

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