Ignition Timing

NOTE: Magnetic probe timing device may be used if instrument is available and engine is so equipped. Timing probe offset is 135° ATDC.

Determine specified timing and mark degree line on damper (on some vehicles mark both pointer and damper notch). Disconnect and plug vacuum line(s) at distributor.
Connect tachometer. Connect timing light to No. 1 spark plug wire. If vehicle is equipped with a barometric sensor, disconnect the sensor from module. Connect Black and Yellow wires in module connector. If vehicle is equipped with EEC-IV, disconnect single wire Black connector near distributor. Set timing to specifications.

IGNITION TIMING SPECIFICATIONS (DEGREES BTDC @ RPM)

Application

Man. Trans.

Auto. Trans.

5.0L ⁽¹⁾

2-Bbl.

10 @ 575

EFI

8 @ Idle

10 @ Idle

5.8L ⁽¹⁾

Light Duty

⁽²⁾ 10 @ Idle⁽¹⁾

⁽²⁾⁽³⁾ 10 @ Idle

Heavy Duty

8 @ 700

8 @ 800

7.5L

8 @ 800

⁽¹⁾	Engines are equipped with Electronic Engine Control (EEC-IV) system. Ignition timing is not a normal adjustment.

⁽²⁾	Federal light duty trucks with 5.8L use Dura-Spark II ignition system.

⁽³⁾	Set Federal High Alt. to 14° @ Idle.