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Ignition Timing

NOTE: Engines are equipped with a receptacle for magnetic probe timing lights, located 10° ATDC. Do not use this location for timing with a conventional light.
  1. Connect an adapter between No. 1 spark plug wire or use an inductive type pickup. Do not puncture wires. Connect timing light according to manufacturer's instructions.
  2. Check or adjust ignition timing with engine at normal operating temperature, distributor vacuum line disconnected and plugged. Light Duty models with automatic transmission should be in "D", all others in neutral.
  3. Set timing to specifications. To adjust timing, loosen distributor hold down bolt and rotate distributor until timing is to specifications. Tighten hold down bolt.
TIMING SPECIFICATIONS (Degrees BTDC@RPM)

Application Man. Trans. Auto. Trans
Light Duty
  5.0L (1) 4@600 (2) 4@600
5.7L
    Federal 8@600 8@500
Calif. ...... 8@550
High Alt. (3) 8@600 8@600
Heavy Duty
  5.7L
    Federal 4@700 4@700
Calif. 6@700 6@700
  7.4L 4@700 4@700
(1) Set decal number CWK to 4° at 700 RPM.
(2) Set decal numbers CMD and CDH to 4° at 500 RPM.
(3) Set decal number CNM to 8° at 700 RPM.
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