How to Adjust the Valves on Chevrolet Cars

by Contributing Writer; Updated June 12, 2017

While it is fairly uncommon to need to adjust valve lash on production Chevrolet car CID small block engines, there are times -- such as after a repair -- that this adjustment is required. Valve lash is the amount of clearance (some, or none) between the intake or exhaust valve and the rocker arm. Without proper clearance, engine performance may be poor or some components could be damaged. Most engines have hydraulic lifters which require no clearance, but mechanical lifter cams do require a small amount. The basic procedure is the same for either type.

Under The Hood:

 How to Adjust the Valves on a Chevy 6 Cylinder 250

Use a ratchet and socket to remove the bolts from the valve cover. Remove the valve cover. Remove the gasket from the valve cover. Scrape any remaining gasket material from the valve cover with a putty knife. Place some shop rags on the cylinder head, next to the head's gasket surface. Scrape any gasket material from the cylinder head with the putty knife. Use the shop rags to prevent any debris from falling into the cylinder head.

Find the timing marker on the left side of the timing cover. Use a ratchet and socket on the large bolt in the center of the crankshaft pulley to rotate the engine in a clockwise direction until the notch in the crank pulley lines up with the "0" on the timing marker. Check to make sure that both valves on the number one cylinder are closed. If not, rotate the crankshaft another complete revolution.

Adjust the number one cylinder intake and exhaust valves by using a ratchet and socket to loosen the adjusting nut in the center of the rocker arm until there is play between the rocker arm and the end of the push rod. Slowly tighten the adjusting nut while spinning the push rod back and forth between your thumb and forefinger. When the push rod stops moving, slowly tighten the nut one additional turn. For 1976-77 engines, turn the adjusting nut 3/4 turn.

Adjust the following valves in the same manner: Intake number two and four. Exhaust number three and five.

Turn the crankshaft one complete turn. The number six cylinder valves should be closed. Adjust both valves in the same manner, then adjust the number three and five intake, and number two and four exhaust.

Spray a shop rag with parts cleaner and clean the gasket surfaces on the valve cover and cylinder head. Apply a coat of gasket sealer to one side of a new valve cover gasket and position the gasket on the valve cover. Coat the exposed surface of the gasket with gasket sealer and install the valve cover onto the cylinder head. Install and tighten the valve cover bolts.

Items you will need

  • Ratchet and socket set

  • Shop rags

  • Putty knife

  • Parts cleaner

  • Valve cover gasket

  • Gasket sealer

 How to Adjust the Valves on a 1999 5.7L Chevrolet Suburban Engine

Start the engine and allow it to reach operating temperature. Shut the engine off and move quickly to step two.

Remove the four bolts securing each of the valve covers and remove the valve covers.

Use a wrench connected to the crankshaft drive gear to turn the engine over until the number one intake valve is at full lift. Adjust the number six intake valve by tightening the intake valve rocker arm nut until the pushrod cannot be spun (signaling that the rocker arm is pressing down on it). Back the rocker arm nut off 1/8-turn.

Continue the process in step three on all intake valves in the following order: number eight intake valve at full lift, adjust number five intake valve; number four valve full lift, adjust number seven valve; number three valve full lift, adjust number two valve; number six valve full lift, adjust number one valve; number five valve full lift, adjust number eight valve; number seven valve full lift, adjust number four valve; number two valve full lift, adjust number two valve.

Use the process in step three to adjust the exhaust valves in the same order as in step four.

Install new valve cover gaskets and reinstall the valve covers.

Items you will need

  • Complete set of US and Metric wrenches and sockets

 How to Adjust the Valves on a 383 Stroker

Hydraulic Tappet Lash Adjustment

Remove the coil wire or otherwise disable the ignition. Remove all wires, lines and accessories that are attached to the valve covers. Remove the valve covers and set aside. Locate the intake and exhaust rocker arms for the No. 1 cylinder. The No. 1 cylinder is on the left side of the front of the 383 Chevy engine.

Rotate the engine so the No. 1 exhaust valve begins to open (depressed down). The intake lifter is on the backside of the cam lobe (base circle) and the valve is fully closed: adjust the intake rocker arm nut so the adjacent pushrod can be just barely rotated with your index finger and thumb. This is "zero-lash," but a hydraulic lifter requires additional pre-load -- tighten the rocker nut one-half turn more. This valve is adjusted. Rotate the engine again in the same direction until the intake valve is almost fully closed.

Perform the same tightening procedure on the exhaust valve/rocker arm ("Exhaust Opening, Intake Closing"), and finish with the one-half extra turn of pre-load.

Continue in the same manner for the remaining cylinders using the "Exhaust Opening, Intake Closing" (EO-IC) sequence.

Reinstall the valve covers and any wires, lines or accessories that were previously removed. (If the old valve cover gaskets have been damaged when removing the valve covers, clean the surfaces and replace with new gaskets.)

Mechanical Tappet Lash Adjustment

Use the same sequence as for the hydraulic cam. Rotate the engine to the "EO" position so the No. 1 intake valve is on its base circle and fully closed.

Insert a feeler gauge between the valve tip and the rocker arm that is approximately .005 inches thicker than the recommended "hot lash" (to allow for parts expansion and clearance reductions when the engine is running).

Tighten the rocker nut so the feeler gauge blade can just barely slide in and out of the lash area. Tighten the rocker nut lock-screw.

Rotate to the "IC" valve position for that cylinder, and set the exhaust lash about .005 inches loose.

Repeat the process for all cylinders, and reinstall the valve covers and wiring.

Items you will need

  • Sockets

  • Ratchet wrench

  • Valve cover gasket set (optional)

  • Feeler gauge (for mechanical tappet engines)

 How to Adjust the Valves on a Chevy 350

Hydraulic Lifter Engines

Disable the ignition system so the engine cannot start when "bumped over" by quickly engaging the starter. Remove the valve covers and set aside. Locate the "number 1" cylinder valves (driver's side, front on Chevrolet V-8s) and identify the intake and exhaust valves. The exhaust valves always correlate to the exhaust port.

Rotate the engine so the number 1 EXHAUST valve begins to OPEN (depressed down). The intake lifter is on the backside of the cam lobe (base circle) and the valve is fully closed: adjust the intake rocker arm nut so the adjacent pushrod can be just barely rotated with your index finger and thumb. This is "zero-lash," but a hydraulic lifter requires additional pre-load -- tighten the rocker nut one-half turn more. This valve is adjusted. Rotate the engine again in the same direction until the INTAKE valve is almost fully CLOSED. Perform the same procedure on the exhaust valve/rocker arm, and finish with the one-half extra turn of pre-load. Continue in the same manner for the remaining cylinders using the "Exhaust Opening, Intake Opening" (EO-IC) sequence.

Reinstall the valve covers -- using new valve cover gaskets, if necessary -- and reattach any wiring that was previously disconnected. Start the engine and observe for any leaks or unusual noises.

Mechanical Lifter Engines

Disable the ignition system so the engine cannot start when "bumped over" by quickly engaging the starter. Remove the valve covers and set aside. Locate the "number 1" cylinder valves (driver's side, front on Chevrolet V-8s) and identify the intake and exhaust valves. The exhaust valves always correlate to the exhaust port.

It's uncommon for engines to have a mechanical tappet (solid lifter) camshaft unless it is an aftermarket upgrade. All procedures and individual sequences are the same except for the "zero-lash" and preload. Mechanical tappet cams require some clearance between the valve tip and rocker arm. Follow the manufacturer's recommendation for the proper amount of hot lash.

Rotate the engine to the "EO" position so the number 1 intake valve is on its base circle and fully closed. Insert a feeler gauge approximately .002 to .005 inch thicker than the recommended "hot lash" to allow for parts expansion and clearance reductions. Tighten the rocker nut so the feeler gauge blade can just barely slide in and out of the lash area between the valve tip and the rocker arm. (Set the lash cold. This is an important tip, as it is difficult top work on a hot engine, and not all settings will be consistent by the end of the procedure.) Once the cold lash is set, tighten the rocker nut. Rotate to the "IC" valve position for that cylinder and set the exhaust lash about .005 inch loose. Repeat the process for all cylinders, and reinstall the valve covers and wiring.

Start the engine and let it warm up to full operating temperature (five to 10 minutes). Listen for any unusual noises; solid lifter cams will "clatter" and this is normal. Shut off the engine and remove the valve covers. Check the valve clearances "hot." Record (in notes) the change in lash and compare it to the recommended hot lash (it should be close to recommended lash now). This will give a good idea of the precise amount of cold lash to use the next time valve lash is set by indicating how far the lash tightens up when hot.

Re-install the valve covers and wiring.

Items you will need

  • Assorted sockets/ratchet wrench

  • Valve cover gasket set

  • Feeler gauge (required for mechanical tappet cams)

About the Author

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