Distributor timing

NOTE: When setting base timing, it is necessary to disconnect the SPOUT circuit. Failure to do so will result in an inaccurate base timing. There are two different types of SPOUT connectors used. The first type is a in-line connector and is simply disconnected for checking the timing. The second type has a shorting bar and the bar is removed from the connector to put the vehicle to base timing. Usally both connectors are located near the distributor refer to "COMPONENT LOCATION". Sorry no pic available

DISTRIBUTOR
All Light Duty models are equipped with the TFI-IV EEC-IV ignition system. All Heavy Duty models are equipped with the Dura-Spark II ignition system. No internal adjustments are required on these systems.

IGNITION TIMING
NOTE:Timing instrument should be connected to No. 1 spark plug wire using an adapter or clip-on connector. Do not puncture spark plug wire or boot to make connection.

Light Duty Models
Turn off all lights and accessories. Set parking brake and place transmission in Neutral (M/T) or Drive (A/T). Ensure A/C and heater are off. Connect timing light and disconnect the single wire in-line spout connector or remove the shorting bar from the double wire spout connector.
Start engine and warm to normal operating temperature. Check timing and adjust if necessary. Reconnect spout connector or reinstall shorting bar. Check timing advance to verify distributor is advancing properly. Remove tachometer and shut off engine.
Heavy Duty Models
Turn off all lights and accessories. Place transmission in Neutral (M/T) or Drive (A/T). Ensure A/C and heater are off. Disconnect and plug vacuum lines at distributor advance connection. Connect timing light and tachometer.
If engine is equipped with a Barometric Pressure Switch, disconnect switch from ignition module and place a jumper wire across the pins at ignition module connector (Black and Yellow wires).
Warm engine to normal operating temperature. With the engine running at specified RPM, adjust ignition timing. Remove all test equipment and reconnect all components.
IGNITION TIMING SPECIFICATIONS
Application. Degrees BTDC @ RPM
All Models.(1) 10 @ 625-725
(1)Refer to Emission Control Label for RPM specification.