Ignition Timing: Adjustments

To obtain optimum engine performance, the distributor must be correctly positioned on the engine to give proper ignition timing.

Test procedures are as follows:

1. Connect an adjustable Timing lamp to number one cylinder (refer to the equipment manufacturer's instructions for correct connecting procedures), or a suitable magnetic timing unit (use a 10° offset when required). Do not puncture cables, boots or nipples with test probes. AlwayS use proper adapters. Puncturing the spark plug cables with a probe will damage the cables. The probe can separate the conductor and cause high resistance. In addition breaking the rubber insulation may permit secondary current to arc to ground.

2. Connect red lead ofthe test tachometer unit to the negative primary terminal of the coil and the black lead to a good ground.

3. Turn selector switch to the appropriate cylinder position.

4. Start engine, set parking brake and place transmission in neutral and run until normal operating temperature is obtained.

Grounding Carburetor Switch:

5. Connect jumper wire between the carburetor switch and a good ground (Fig. 7).

6. Read the engine rpm on the 1000 rpm scale. If the engine rpm is at or below the curb idle rpm specified on the label, proceed to next step.

If it is higher, reduce rpm until the specified curb idle rpm is reached.

Magnetic Timing Probe Receptacle Eight Cylinder Engine:

7. Aim timing light at timing plate on chain case cover or read magnetic timing unit (Fig. 8). If timing is within +/- 2° of value specified on the label, proceed to step (9). If outside of specified tolerance, proceed to next step.

8. Loosen distributor hold-down arm screw just enough so the distributor housing can be rotated in its mounting. Turn distributor housing until, specified label value is reached. Tighten the hold- down arm screw and recheck timing. When timing is acceptable (+/- 2°), recheck curb idle rpm. If engine rpm is not at or below the curb idle rpm shown on the label, reset engine rpm and recheck timing. Repeat above until both engine rpm and timing are acceptable.

9. Remove timing light or magnetic timing unit.

10. If curb idle rpm is not within +/-50 rpm of value shown on label readjust curb idle rpm. Do not reset timing.

11. Turn the engine off. Unplug and reconnect vacuum line at distributor, if disconnected. Remove the jumper wire (if installed) and tachometer.