How to adjust the timing on a 1967 Shelby GT500?

Adjusting the timing on a 1967 Shelby GT500 is an essential task to ensure optimal performance and engine health. Incorrect timing can cause poor fuel efficiency, engine knock, and a lack of power. Typical symptoms indicating timing issues include rough idling, difficulty starting, and abnormal engine noises. Proper timing adjustment can restore the engine to its optimal operating condition. Here is how to solve this issue:

Step 1: Gather Necessary Tools

Before you start, make sure you have the required tools:

• Timing light: Used to check the timing mark while the engine is running.
• Wrench set: Required to loosen and tighten the distributor hold-down bolt.
• Screwdrivers: Flathead and Phillips may be needed for various adjustments.
• Chalk or white paint marker: To mark the timing scale for better visibility.

Step 2: Locate the Timing Marks

Open the hood and locate the timing marks on the engine block. These marks are typically found on the harmonic balancer (a round, pulley-like device connected to the crankshaft at the front of the engine). Shine a light on the harmonic balancer and look for a small notch or line. Use chalk or a white paint marker to highlight this notch for easier viewing.

Step 3: Find the Pointer

Next, locate the timing pointer, a metal tab attached to the timing cover around the harmonic balancer area. The pointer often has a scale marked in degrees. Make sure this area is clean and the numbers are visible. Use a rag to wipe off any oil or dirt.

Step 4: Warm Up the Engine

Start the engine and allow it to reach normal operating temperature. This step ensures that the timing is adjusted under the same conditions the engine will be operating in. Listen for any unusual sounds or vibrations.

Step 5: Connect the Timing Light

Connect the inductive pickup of the timing light to the number one spark plug wire. The number one spark plug is usually the front-most plug on the driver's side of the engine on a V8. Connect the timing light’s power cables to the battery – red to positive and black to negative.

Step 6: Set Base Timing

With the engine running at idle, point the timing light at the harmonic balancer scale. The flashing light will make the notch appear stationary. Check the current timing reading. For a 1967 Shelby GT500, the factory timing specification is generally 10-12 degrees Before Top Dead Center (BTDC).

Step 7: Adjust the Timing

Loosen the distributor hold-down bolt slightly using a wrench. The distributor is located at the rear of the engine, near the firewall. As you turn the distributor, the timing will advance (if turned counterclockwise) or retard (if turned clockwise). Adjust until the timing notch aligns with the desired mark on the timing scale (e.g., 10-12 degrees BTDC).

Step 8: Secure the Distributor

Once the timing is correctly set, hold the distributor in place and tighten the hold-down bolt securely. Ensure the distributor does not move as you tighten the bolt, as this could alter the timing.

Step 9: Re-check the Timing

Double-check the timing with the light to confirm it hasn’t moved. Make any fine adjustments if necessary and ensure the bolt is fully tightened.

Step 10: Complete the Process

Turn off the engine and disconnect the timing light. Re-check all connections and re-secure any removed components or cables. Your Shelby GT500 should now have its timing set correctly, leading to smoother operation and improved performance.

By following these steps, you can ensure your 1967 Shelby GT500 runs smoothly and efficiently. Always consult your vehicle’s service manual for any specific details or variations.