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Home›Repair guides›General Motors›HEI Distributor Timing Procedure

General Motors — HEI Distributor Timing Procedure

Adjustments · Ignition distributor

From a General Motors operator's manual covering: 181 CID, 3.0L L4, GMG-430, LW6. Check it applies to your exact model before use.

Applies to: General Motors 3.0L L4 (181 CID) engine

Before you start

  • Piercing secondary insulation will cause spark plug misfiring and may damage internal conductor.
  • Do not connect initial timing connector to B+ while starting engine; may damage ICM.

Procedure

  1. Do not use timing light that requires piercing secondary insulation. Use only inductive pick-up or jumper type connectors.
  2. Install timing light at #1 spark plug lead per manufacturer's instructions.
  3. Do not connect alligator clip lead of initial timing connector to B+ source until after engine is started. If connected while starting, ICM in distributor may be damaged.
  4. Start engine and allow warm to operating temperature. Connect alligator clip on long lead of initial timing connector to B+ voltage source, such as battery terminal on starter solenoid. This removes a
  5. Engine speed should be around 650 RPM. Loosen distributor clamp screw just enough to rotate distributor, and set base timing to specification shown for engine.
  6. Industrial do not exceed: 454 initial 6° total 30°; 350 initial 6° total 28°; 262 initial 2° total 26°; 181 initial 0° total 20°.
  7. Set idle speed to 700 RPM ± 50 RPM.
  8. When timing is set, secure distributor in position with clamp screw. Tighten clamp screw to torque specified.
  9. Recheck timing to assure distributor did not move during tightening.
  10. Disconnect initial timing connector from B+ source. Label initial timing connector as shown, keeping with engine for future use.

Tools required

  • Timing light with inductive pick-up or jumper type connectors

Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.

Specs & values

  • 181: initial 0°, total 20°
  • 262: initial 2°, total 26°
  • 350: initial 6°, total 28°
  • 454: initial 6°, total 30°
  • Idle speed 700 ± 50 RPM
  • Engine speed during timing ~650 RPM

Source: General Motors operator's manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.

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