How to adjust valve clearance on a 1970 Chevrolet Chevelle SS 454?

Adjusting the valve clearance on a classic 1970 Chevrolet Chevelle SS 454 is crucial for maintaining optimal engine performance. Incorrect valve clearance can lead to poor engine performance, increased emissions, and potential engine damage. You may notice a tapping noise from the valve train or experience rough idling, suggesting that an adjustment is required. To solve this issue, follow these detailed steps:

Step 1: Gather Necessary Tools
Before you start, ensure you have the following tools:

• Feeler gauge
• Socket set with a ratchet
• Screwdriver
• Wrenches
• Valve cover gasket set
• Shop manual for reference

Step 2: Preparation
Start by parking your Chevelle on a flat, level surface and allow the engine to cool down if it has been running. Disconnect the negative terminal of the battery to ensure safety.

Step 3: Remove the Valve Covers
The valve covers are located on top of the engine, covering the rocker arms and valves. They are rectangular and secured by multiple bolts around their perimeter. Use a socket wrench to loosen and remove these bolts. Carefully lift the valve covers off, and place them aside.

Step 4: Locate Top Dead Center (TDC) for Cylinder 1
Rotate the engine using a wrench on the crankshaft pulley bolt located at the bottom front of the engine. Turn the engine clockwise until the mark on the pulley lines up with the “0” mark on the timing tab, and ensure that Cylinder 1 is in the compression stroke. You can verify this by removing the spark plug from Cylinder 1 and feeling for pressure build-up in the cylinder.

Step 5: Adjust Valve Clearance for Cylinder 1
With Cylinder 1 at TDC on the compression stroke, locate the rocker arms connected to the valves of Cylinder 1. Using a feeler gauge, measure the gap between the rocker arm and valve stem. The correct clearance typically ranges between 0.008 inches for intake and 0.018 inches for exhaust (check your shop manual for precise specifications). Loosen the lock nut on the rocker arm stud with a wrench and adjust the screw until the feeler gauge slides through with slight resistance. Tighten the lock nut while holding the adjustment screw in place.

Step 6: Rotate the Engine and Repeat
Rotate the engine 90 degrees clockwise to bring the next cylinder in the firing order to TDC. The firing order for a 454 engine is 1-8-4-3-6-5-7-2. Follow this sequence and adjust the valve clearances for each cylinder repeating the same process as in Step 5.

Step 7: Reinstall the Valve Covers
Once all valve clearances have been adjusted, clean the mating surfaces of the valve covers and cylinder heads. Place new gaskets on the valve covers to ensure a proper seal, then re-secure the valve covers to the engine using the bolts removed earlier. Tighten the bolts evenly to avoid warping the covers.

Step 8: Reconnect the Battery and Test
Reconnect the negative battery terminal. Start the engine and let it idle. Listen for any unusual noises and ensure the engine is running smoothly. A successful adjustment should result in quieter operation and improved performance.

By following these steps, you can ensure the valves on your 1970 Chevrolet Chevelle SS 454 are properly adjusted for optimal engine function and longevity.