How to set the Ignition Timing?

Here is a video to show you how to timing the big block:

https://youtu.be/ozdvwnRlOas?si=yUpypceaOsL7khs1

Here is additional information:

NOTE: Timing specifications are listed on the Vehicle Emissions Control Information label under the hood. Always follow the Vehicle Emissions Control Information label procedures first before using the following procedure.

PROCEDURE:

Set timing under the following conditions:

Normal operating temperature.
Air cleaner installed.
A/C "OFF".
Transmission in neutral.
Disconnect SET TIMING connector (tan/black wire) located in harness close to distributor. DO NOT disconnect 4 wire connector at distributor.

Connect timing light and adjust as necessary by loosening hold down bolt and rotating distributor. For specification, refer to SPECIFICATIONS/ELECTRICAL AND ELECTRONIC SPECIFICATIONS/TIMING SPECIFICATIONS. Tighten hold down and recheck the timing. Stop the engine and connect SET TIMING connector. Clear ECM trouble code by disconnecting ECM power source.

NOTE: Dual timing scribes are on the 4.3L engine balancers. They line up with the timing indicators at one o'clock and four o'clock positions. Use the one o'clock position.

Check out the images (below). Let us know if you need anything else.