Ignition Timing: Adjustments

Ignition System Timing

Timing Mark - 6 Cylinder Engine:

A graduated timing degree scale located on the timing case cover is used for timing each ignition system. An index notch milled into the vibration damper is used to reference the No. 1 cylinder ignition position of the crankshaft with the correct timing mark on the graduated scale.

Magnetic Timing Probe

A socket integral with the timing degree scale on the timing case cover is provided for use with a special magnetic timing probe that detects the milled notch in the vibration damper. The probe is inserted through the socket until it touches the vibration damper and is automatically spaced away from the damper by damper eccentricity. Ignition timing is indicated on a meter or computer printout, depending on the manufacturer's equipment.

The socket is located at 9.5° ATDC, and the equipment is calibrated to compensate for the degree difference. Do not use the socket location when timing an ignition system with a conventional timing light.

Ignition Timing Procedure

Refer to Tune-Up Specification charts and Emission Control Information label located in the engine compartment.

1. Disconnect and plug distributor vacuum advance hose opening.
2. With ignition switch off, connect ignition timing light and properly calibrated tachometer.

NOTE: If the timing light has an adjustable advance control feature, turn the control to the OFF position.

3. Disconnect two-wire connector (yellow and black wires) at electronic ignition module and short circuit ignition module connector terminals with jumper wire.

NOTE: When the ignition module connector terminals are short circuited with the jumper wire the electronic retard circuit is deactivated. This is necessary to accurately adjust the ignition timing.

WARNING: Use extreme caution when engine is operating. Do not stand in direct line with fan. Do not put hands near pulleys, belts or fan. Do not wear loose clothing.

4. Engage parking brake, start engine and allow to warm up to normal operating temperature. Place automatic transmission in Drive, manual transmission in Neutral position.
5. Adjust idle speed to specified curb (slow) idle rpm. Refer to Tune-Up Specifications charts and Emission Control Information label.

WARNING: Use extreme caution when engine is operating. Do not stand in direct line with fan. Do not put hands near pulleys, belts or fan. Do not wear loose clothing.

6. Adjust ignition timing to degrees specified in Tune-Up Specifications-On Vehicle chart by loosening distributor holddown clamp and rotating distributor.
7. Increase engine speed to 1600 rpm while observing and adjusting ignition timing.
8. Tighten distributor holddown clamp and verify that ignition timing is correct.
9. Turn off engine and remove timing light and tachometer. Connect No. 1 spark plug wire, if disconnected. Connect hose to distributor vacuum advance mechanism. If applicable, remove jumper wire and connect electronic ignition module connector to wire harness connector.