How to adjust valve clearance on a 1967 Shelby GT500?

Model: 1967 Shelby GT500

Experiencing uneven engine performance or a ticking noise from your classic 1967 Shelby GT500 could indicate improper valve clearance. This adjustment is vital to ensure the correct operation of the engine's valves, promoting optimal performance and longevity. Here's how to solve this issue:

Step 1: Gather the Necessary Tools

Before you begin, you'll need some specific tools:

Feeler gauges
A socket wrench set
A flat-head screwdriver
A torque wrench
A valve cover gasket (optional but recommended to have on hand)

Step 2: Locate and Remove the Valve Covers

The valve covers are located on top of the engine, with one on each side of the V8 engine. They are rectangular in shape and have multiple bolts securing them.

Use your socket wrench set to carefully remove the bolts around the perimeter of the valve covers.
Lift off the valve covers and set them aside, ensuring not to damage any gaskets.

Step 3: Rotate the Engine to Top Dead Center (TDC)

To adjust the valve clearance correctly, the engine must be at TDC for the cylinder you're working on.

Use the socket wrench on the crankshaft pulley bolt to rotate the engine.
Observe the timing marks on the harmonic balancer and align them with the TDC mark on the timing cover. You might need a flashlight to see these marks clearly.

Step 4: Identify the Valves and Measure the Clearance

With the engine at TDC, you should have two valves visible per cylinder – an intake and an exhaust valve.

Insert the correct feeler gauge between the rocker arm and the valve stem.
For a 1967 Shelby GT500, the typical valve clearance is around 0.019 inches for both intake and exhaust when the engine is cold.

Step 5: Adjusting the Valve Clearance

Once you've measured the existing clearance, you may need to adjust it.

Using the flat-head screwdriver, turn the adjusting screw located at the tip of the rocker arm.
Carefully turn the screw until you achieve the correct clearance as per the feeler gauge.
It should slide in with slight resistance but without bending.

Step 6: Double-Check Your Work

After adjusting, double-check the clearance with the feeler gauge to ensure it is accurate.

Repeat the process for each of the valves by rotating the engine to TDC for the next cylinder in the firing order and repeating the adjustment steps.

Step 7: Reassemble Everything

Once all adjustments are made:

Clean the mating surfaces on both the cylinder head and the valve covers to ensure no oil or debris remains.
If needed, replace the valve cover gaskets to prevent oil leaks.
Carefully place the valve covers back in position and secure them with bolts using the torque wrench, ensuring even pressure distribution.

By following these steps meticulously, you can ensure your 1967 Shelby GT500's valve clearance is properly adjusted, leading to a smoother running engine and extending the life of your classic muscle car.