General Motors — Setting ignition (EST) base timing
Adjustments · Distributor / ignition system
From a General Motors operator's manual covering: 4.3L 262 CID, 4.3L V6, GMG-643. Check it applies to your exact model before use.
Before you start
- Do not connect alligator clip lead of the initial timing connector to a B+ source until after engine is started or the ICM may be damaged.
- Do not use a timing light that requires piercing of the secondary insulation.
Procedure
- Do not use a timing light that requires piercing of secondary insulation; use only a timing light with inductive pick-up or jumper type connectors.
- Install the timing light at #1 spark plug lead per manufacturer's instructions.
- Start the engine and allow it to warm to operating temperature.
- Connect the alligator clip on the long lead of the initial timing connector to a convenient B+ voltage source such as the battery terminal on the starter solenoid.
- Loosen the distributor clamp screw just enough to rotate the distributor and set base timing to specification shown for engine.
- When timing is set to specification secure the distributor in position with the clamp screw.
- Tighten the clamp screw to the torque specified.
- Recheck timing to assure the distributor did not move during tightening.
- Disconnect the initial timing connector from B+ and remove the connector from the distributor; label and store it.
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
- 262 INITIAL 2 degrees TOTAL 26 degrees
- Set idle speed to 700 RPM +/- 50 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.