Setting the ignition timing to fire the spark plugs at the right moment is an important part of performing a tune-up on your 5.7 liter equipped 1992 GM truck. Normal engine wear will cause small changes in the ignition timing that can be corrected by setting the timing back to factory specifications. This procedure requires no parts replacement and the average home mechanic will complete the job in about half an hour using basic hand tools and a timing light.
Unscrew the wing nut that attaches the air cleaner to the throttle body. Unplug the vacuum lines under the air cleaner and lift the air cleaner off the throttle body. Plug the disconnected vacuum lines with golf tees.
Start and warm the engine until normal idle speed occurs. Attach the timing light to the battery and the front spark plug wire on the driver side of the engine. Turn the engine off. Unplug the the single wire timing connector found taped to the wiring harness that runs along the back of the fire wall.
Loosen the distributor by loosening the 9/16-inch bolt on the hold down bracket at the base of the distributor housing. Start the engine. Aim the timing light at the timing pointer on the front of the timing cover and rotate the distributor to adjust timing. Align the mark on the harmonic balancer with the 12 degrees notch on the timing pointer. Tighten the distributor hold down bracket bolt.
Turn off the engine and reinstall the air cleaner. Plug the timing connector back in and test drive the vehicle.
