Here's a general overview. Specific procedures will vary depending on the engine (small block, big block, etc.) in your Chevelle. Always consult a shop manual specific to your year and engine for precise instructions, torque specifications, and diagrams. A Haynes or Chilton manual is a good investment.
Tools You'll Likely Need:
* Shop Manual: Absolutely essential!
* Valve adjustment wrench: The size will depend on your engine.
* Feeler gauges: A set covering the range of valve clearances specified in your shop manual.
* Socket set: For removing rocker arm covers and possibly other components.
* Wrenches: Various sizes for other bolts and nuts.
* Breaker bar or ratchet: To help loosen stubborn bolts.
* Pry bar (optional): Might be needed to gently pry rocker arms.
* Torque wrench: Essential for tightening bolts to the correct specifications.
* Gloves and safety glasses: Always protect yourself!
General Steps (These are highly generalized and will vary by engine):
1. Identify Your Engine: Small block (typically 283, 307, 327, 350 cubic inches) or big block (typically 396, 402, 427, 454 cubic inches)? The procedure will differ significantly.
2. Consult Your Shop Manual: Find the section on valve adjustment. This will detail the exact procedure for *your* engine. It will specify:
* Valve lash (clearance): The precise measurement (in thousandths of an inch or millimeters) needed between the valve stem and rocker arm.
* Firing order: The sequence in which cylinders fire. This is crucial for setting the engine to the correct top dead center (TDC) for each cylinder.
* Engine timing marks: How to locate TDC on your engine.
* Correct tightening torque for all fasteners.
3. Preparation:
* Disconnect the battery's negative terminal.
* Drain the engine oil (recommended, but not always necessary).
* Remove the valve covers. This provides access to the rocker arms and valve train.
4. Find Top Dead Center (TDC): Using the crankshaft pulley and timing marks on the engine, locate the TDC position for each cylinder, following the sequence indicated in your shop manual. This is the most critical step; an incorrect position can lead to serious damage.
5. Adjust Valves: For each cylinder, at TDC, you'll use the feeler gauge to check the valve lash (clearance). You'll adjust the rocker arm using the adjustment wrench until the feeler gauge slides through with the correct amount of resistance. This will usually involve loosening a lock nut, adjusting the push rod, and then retightening the lock nut. Repeat for both the intake and exhaust valves of each cylinder.
6. Reassemble: Replace the valve covers, ensuring a good gasket seal. Reconnect the battery.
7. Check Your Work: After reassembly, check again for any unusual noises. You may want to take it for a test drive, but keep it gentle initially.
Important Warnings:
* Incorrect valve adjustment can seriously damage your engine. Take your time, be precise, and double-check your work.
* Always use the correct tools and torque specifications.
* If you're unsure about any step, consult a professional mechanic. It's much cheaper to pay a mechanic than to rebuild an engine.
This is a simplified overview. The exact procedure is complex and engine-specific. Using a shop manual appropriate for your specific 1971 Chevrolet Chevelle engine is absolutely essential. Don't attempt this without one.
