Tools You'll Need:
* Factory Service Manual: Absolutely essential.
* Valve Adjusting Wrench: The correct size for your rocker arm nuts. Often a combination wrench or socket works best.
* Feeler Gauges: A set of feeler gauges in the appropriate range for your engine's valve lash specifications (usually .016" - .020" intake and .020" - .024" exhaust for a hydraulic cam, but check your manual).
* Socket Set and Wrenches: For removing the valve covers.
* Torque Wrench: For tightening valve cover bolts to the manufacturer's specified torque.
* Breaker Bar (Optional): May be necessary to break loose stubborn rocker arm nuts.
* Shop Rags: To keep the engine clean.
* Pry Bar (Optional): Can help to gently pry the rocker arms if needed.
Procedure:
1. Safety First: Disconnect the negative battery terminal before starting any work.
2. Locate Top Dead Center (TDC): This is crucial. You need to find TDC on the #1 cylinder compression stroke. Use your factory service manual's instructions to ensure you're at the right spot. This often involves using a timing light or turning the engine over by hand until the timing marks align.
3. Remove the Valve Covers: Carefully remove the valve covers. Clean them thoroughly.
4. Identify Intake and Exhaust Valves: Each rocker arm controls either an intake or exhaust valve. Refer to your service manual for a diagram if needed.
5. Adjust the Valves:
* Hydraulic Lifters (Most Common): Hydraulic lifters automatically adjust, so you're not setting the clearance as with solid lifters. Instead, the procedure typically involves ensuring zero lash. This usually means slightly loosening the rocker arm nut, then tightening it until all play is removed and then tightening it another specified amount (usually a fraction of a turn after you remove all play). Your manual details this process.
* Solid Lifters (Less Common): This involves inserting the correct feeler gauge between the valve stem and the rocker arm, then adjusting the rocker arm nut until you feel the specified resistance of the feeler gauge. This requires more precision. Again, refer to your service manual.
6. Rotate the Engine: After adjusting the valves on one cylinder, rotate the crankshaft 360 degrees (two full turns) to the next cylinder's TDC compression stroke. This is typically accomplished with a wrench on the crankshaft pulley. Repeat this procedure for each cylinder until all valves are adjusted. You will adjust intake and exhaust valves on each cylinder at the same time while at TDC.
7. Reinstall Valve Covers: Replace the valve covers and tighten the bolts to the specified torque using your torque wrench.
8. Recheck: After you've adjusted all the valves, it's wise to go back and double-check your work.
9. Reconnect Battery: Reconnect the negative battery terminal.
Important Considerations:
* Engine Temperature: Some recommend performing this procedure on a warmed-up engine to minimize distortion. Others suggest a cold engine. Check your manual for the preferred method.
* Listen for Tapping: After the adjustment, start the engine and listen carefully for any unusual tapping sounds. This could indicate an improperly adjusted valve.
* Professional Help: If you are not comfortable performing this task, it's best to take your car to a qualified mechanic. Incorrect valve adjustment can lead to severe engine damage.
Remember, this is a general guide. Always consult your 1970 Chevy 350's factory service manual for specific instructions and specifications. The manual is your bible for this job. Ignoring its instructions could result in engine damage.
