Here's a general outline. Specific procedures may vary slightly depending on the year and model of your Mustang:
Tools You'll Need:
* Timing light: Essential for accurately reading the timing.
* Socket wrench and extensions: To reach the distributor.
* Distributor hold-down clamp (optional but recommended): To prevent accidental movement of the distributor.
* Spark plug wire remover: To make accessing the distributor easier.
* Owner's manual or a reliable workshop manual specific to your Mustang's year: This will give you the exact specifications for your engine. The timing specifications can vary depending on the year and options (e.g., automatic vs. manual transmission, carburetor vs. fuel injection).
* Safety glasses: Protect your eyes from potential debris.
Steps:
1. Preparation:
* Safety First: Disconnect the negative battery terminal. This prevents accidental shorts and protects you from electric shock.
* Engine Temperature: The engine should be at operating temperature (ideally after a good drive). This ensures accurate readings. However, you don't want the engine dangerously hot.
* Access: Get comfortable access to the distributor and the timing marks on the harmonic balancer (or crankshaft pulley).
2. Locate Timing Marks: Find the timing marks on the harmonic balancer (the pulley on the crankshaft) and the pointer on the timing cover. These marks will usually indicate degrees Before Top Dead Center (BTDC). Your owner's manual will show you the exact location.
3. Connect the Timing Light: Clip the timing light's inductive clamp around a spark plug wire (usually the #1 cylinder wire). Connect the timing light to a power source (usually the battery).
4. Set the Idle Speed: Adjust the idle speed to the factory specification as found in your owner's manual. This is important for an accurate timing reading.
5. Observe the Timing: Have a helper crank the engine, and shine the timing light onto the harmonic balancer. The light will "freeze" the timing mark, allowing you to read the timing. The mark should align with the degrees BTDC specified in your owner's manual. This is usually around 8-12 degrees BTDC for a 289, but consult your manual.
6. Adjust the Timing (If Necessary): If the timing is off, loosen the distributor hold-down clamp (if using one). Very carefully rotate the distributor slightly to adjust the timing. Use small increments and check the timing with the light after each adjustment. Only adjust the distributor slightly; large adjustments can be detrimental.
7. Re-Check and Tighten: Once the timing is correct, tighten the distributor hold-down clamp. Re-check the timing to ensure it hasn't moved.
8. Reconnect Battery: Reconnect the negative battery terminal.
Important Considerations:
* Vacuum Advance: Many 289 Mustangs have a vacuum advance mechanism on the distributor. Ensure this is connected and functioning correctly; it will alter timing based on engine load. Some instructions may advise disconnecting it while setting base timing (the timing at idle). Your manual will guide you here.
* Distributor Rotation: Rotating the distributor clockwise advances the timing, and counter-clockwise retards it.
* Dual Point Distributors: If your car has a dual point distributor, the timing may be more challenging to set accurately, and require more fine-tuning adjustments.
This is a general guide. Again, refer to your owner's manual or a reliable workshop manual for your specific 289 Mustang's specifications and detailed instructions. If you are not comfortable with this procedure, seek the assistance of a qualified mechanic. Incorrectly setting the timing can lead to engine damage.
