Ignition Timing

NOTE: Engines are equipped with a receptacle for a magnetic probe timing light, located 9.5° ATDC. Do not use this location for timing with a conventional light.

Ignition timing procedures will vary with vehicle model and component application. Refer to Emissions Control Decal in engine compartment for correct adjustment procedures and proceed as follows:

Set parking brake and block drive wheels. Timing is checked and adjusted with engine at normal operating temperature, choke open and A/C off. Place transmission in Park or Neutral.
Disconnect and plug vacuum line to air cleaner. Remove air cleaner. On 4.9L Turbo models, connect a jumper wire between ground and the distributor by-pass connector (Blue). On 6.0L models, disconnect reference signal connector (Green) on left side of engine. Do not ground either side of connector.
On all other models, disconnect 4-wire connector at base of distributor. Check or adjust timing at idle or specified RPM. After adjustment, return wiring to original condition and reinstall air cleaner.

Ignition Timing (Degrees BTDC@ldle)

Application

Man. Trans.

Auto. Trans.

4.3L (260")

.....

⁽¹⁾⁽²⁾18

4.3L (265")

4.4L (267")

4.9L (301") 4-Bbl.

4.9L (301") Turbo

5.0L (305")

5.0L (307")

⁽¹⁾15

5.7L (350")

6.0L (368")

⁽¹⁾	Set timing at 1100 RPM in Park.

⁽²⁾	Set Cutlass (exc. wagon) to 20° BTDC.