Ignition Timing: Adjustments

1. Warm up the engine to the normal operating temperature.
2. Connect a tachometer to the engine.
3. Connect a timing light to high tension lead of the leading spark plug on the front rotor housing.
4. Start the engine and adjust idle to specified idle speed.

Fig. 11 Measuring ignition timing:

5. Aim the timing light at the timing indicator pin on the front cover. Fig. 11.

Ignition timing: (ATDC)
Trailing 12A engine 20° 13B engine 20°
Leading 12A engine 0° 13B engine 5°

6. If the leading timing is not correct, loosen the distributor lock nut and rotate the distributor housing until the correct leading timing is obtained.
7. Tighten the distributor lock nut, and recheck the leading timing.
8. Connect the timing light to the high tension lead of the trailing spark plug on the front rotor housing.
9. Check the trailing timing.
10. If the trailing timing is not correct, loosen the trailing vacuum unit attaching screws and move the vacuum unit until the correct trailing timing is obtained.
11. Tighten the vacuum unit attaching screws and recheck the trailing timing.

Fig. 8 Spark advance curves:

12. Check the advance characteristic by increasing engine speed and noting the change in ignition timing. Fig. 8.
13. Disconnect the timing light.