How to Adjust a Valve Lash in Vehicles

by Contributing Writer

The hydraulic lifter has a main cylindrical body with an internal plunger. When it fills with oil it uses pressure to automatically adjust Vehicles zero valve lash, which keeps all the valves opening and closing in perfect timing. The camshaft rotates to move the lifter, which forces pressure on the push rod. The push rod connects to a spring, which instantly forces the valve shut. Not too much can wrong with hydraulic lifters except Vehicles normal wear, and then they need to be adjusted. You can adjust the valve lash in your Vehicles without resorting to an auto repair shop.

Under The Hood:

 How to Adjust a Valve Lash With a Solid Cam

Read the camshaft box specifications label for the proper valve adjustment amount. If this is not available, call either a speed shop or the camshaft manufacturer for these figures. The intake and exhaust figures will vary with different engines. Check the engine to make sure it is absolutely cold. The valves can't be adjusted warm.

Connect the remote starter switch by attaching one lead to the positive terminal on the battery and the second lead to the small wire terminal on the starter solenoid. This terminal is labeled the S terminal.

Loosen all the valve adjusters with the 5/8-inch wrench until they have a small amount of freeplay. This method of adjusting rocker arms on a solid lifter cam begins with the closest valve to the radiator on either side of the engine and works rearward on each cylinder head.

Push down slightly on the pushrod end of the rocker arm, just enough to keep the rocker arm in contact with the pushrod. Bump the engine over in short increments with the remote starter switch. Every time you depress the remote starter switch, the engine will rotate a small amount. Repetitively depress the button on the switch to rotate the engine while paying attention to the rocker arm. The pushrod side of the rocker arm must rise and begin to drop. Continue to momentarily bump the switch until the pushrod goes all the way down and the next bump results in no movement of the pushrod. The valve lifter should appear on the heal (low side) of the camshaft where it needs to be to adjust the valves. This procedure must be done on each rocker arm prior to adjustment.

Insert the appropriate size feeler gauge between the rocker arm and the top of the valve. It may be necessary to loosen the valve adjuster slightly to allow the feeler gauge to slide between the rocker arm and valve. Slowly tighten down on the adjustment nut until there is a slight drag on the feeler gauge when sliding it in and out between the valve and rocker arm. When properly adjusted you should be able to remove and replace the feeler gauge with slight difficulty. Move on to the next valve and repeat this procedure until all the valves have been adjusted.

Remove the remote starter switch.

Items you will need

  • 5/8-inch open and closed end wrench

  • Set of feeler gauges

  • Remote starter switch

 How to Adjust Valve Lash on a Pontiac Engine

Place the vehicle in park or neutral and set the emergency brake. Raise the hood and prop it open. Leave the battery connected. Make sure the engine has warmed up but is just beginning to cool off. Note the components that sit above the valve cover or, on V-8 or V-6 engines, the valve covers.

Use a socket and wrench to loosen and remove the bolts or screws securing the air box hose; the plastic engine cover, or plenum; the PCV valve and hose; the throttle cable; the vacuum hoses; and any component impeding access to the valve cover. Refer to your owner's repair manual for these components, their fastener types and locations. Make note of the adjustment setting on the throttle linkage so that you can reinstall it properly.

Use a socket and wrench to remove the valve cover bolts on the engine. For V-6 and V-8 models, remove only one valve cover at a time to perform the procedure. Keep the bolts in order; remember their hole location and any bracket that they held. Pull the valve cover off the engine. Be sure not to damage the valve cover gasket. Start at one end of the engine and place a tappet clip on the first rocker arm tappet.

Fasten the tappet clip around the tappet so the oil plug fits into the tappet oil hole. You may fit the rest of the rocker arm tappets with clips, to keep the oil spray to a minimum. Start the engine. Starting at the first rocker arm tappet, loosen the locking nut on the rocker arm with an end wrench, just enough to back it off. Keep the end wrench secured around the lock nut.

Use a large flat-head screwdriver to turn the adjusting screw counterclockwise just until you hear the rocker arm begin to clack. Turn the adjusting screw clockwise 1/4 turn and hold it while you tighten the locking nut clockwise -- this seats the hydraulic lifter to "0" lash. Perform the identical procedure on the next rocker arm. After you have moved halfway down the bank of the engine doing the adjustments, remove the tappet clips to let the rocker arm shaft lubricate for a minute, then replace them.

Remove the second valve cover if you have a V-6 or V-8 and perform the same procedure. When finished with the adjustments, shut the engine off and remove all of the tappet clips. Wipe down any sprayed oil on the gasket. Replace the valve cover and insert the bolts. Tighten the valve cover bolts firmly and evenly with a socket and wrench.

Clean any sprayed oil on the exhaust or intake manifold with carburetor cleaner and a rag. Insert the bolts and screws onto any components you removed above the valve covers and tighten them with a screwdriver or socket. Start the engine and let it run. Some oil smoke will be normal; it will eventually burn off.

Items you will need

  • Owner's repair manual

  • Rags

  • Socket set

  • Ratchet wrench

  • Screwdrivers

  • Combination end wrenches

  • Tappet oil clips

  • Carburetor cleaner

 How to Adjust the Valve Lash on a Big Block Ford

Remove the valve covers by removing the 3/8-inch attaching bolts with a socket and socket wrench. Valve covers that are stuck to the cylinder head can be freed by prying them loose with a large screwdriver. Loosen the rocker arm adjusting nuts, located on the rocker arm stud, that attach the rocker arm to the cylinder head. Remove the spark plugs to make turning the engine easier.

Turn the engine, with a 3/4-inch socket and socket wrench, until the exhaust-valve lifter on the number one cylinder (front cylinder on the left side of the engine) just begins to move up. Adjust the rocker arm to zero clearance. Zero clearance is met when the push rod has a slight drag on it from contact with the rocker arm and lifter. At this point there should be no free play in the rocker arm. Turn the adjusting nut 1/4-turn more to pre-load the lifter.

Turn the engine again until the intake valve lifter on the number one cylinder just stops moving down. Tighten the rocker arm adjusting nut to zero clearance. Tighten 1/4-turn more to pre-load the lifter. Repeat step 2 and 3 on the remaining seven cylinders. Re-check all of the adjustments to verify they are correct, and readjust as needed

Reinstall the valve covers using new gaskets, and tighten the valve cover retaining bolts snugly. Avoid over-tightening the bolt as this will split the gaskets and cause oil leaks. Start the engine, check for leaks and test drive to verify the adjustment. Excessive lifter noise or backfiring indicates misadjustment. Readjust as needed.

Items you will need

  • Socket set

  • Wrench set

  • Screwdriver set

  • Shop rags

  • Valve cover gaskets

  • Service manual

 How to Adjust a Valve Lash on a Chevy 350 CID Engine

Hydraulic Tappet Camshafts

Adjust the “pre-load” with the following procedure (engine OFF, valve covers removed):\n\nPlace a socket and wrench on the crankshaft bolt or snout, and rotate the engine clockwise until the No. 1 piston is at top dead center (TDC). (The No. 1 cylinder is the driver’s side front cylinder.)

Tighten the rocker nut on the No. 2 cylinder INTAKE rocker arm with a socket wrench while rotating the pushrod between your index finger and thumb until the pushrod becomes just difficult to rotate. The valve is now at zero-lash, but the lifter is not yet pre-loaded.\n\n(Hydraulic lifters are designed so that the lifter itself provides the take-up of any lash. As a result, they have a spring and oil pressurized plunger within them that needs to be “pre-loaded.”)\n\nRepeat this procedure with the No. 7 INTAKE and No. 4 and No. 8 EXHAUST rocker arms.\n\nRotate the crankshaft clockwise precisely 180 degrees. Repeat the procedure for INTAKE rocker arms No. 1 and No. 8, and EXHAUST rockers No. 3 and No. 6.\n\nRotate another 180 degrees and set INTAKES Nos. 3 and 4 and EXHAUST rockers Nos. 5 and 7.\n\nAfter rotating the final 180 degrees (two complete rotations of the crank), set the Nos. 5 and 6 INTAKES and the Nos. 1 and 2 EXHAUST valves.

Tighten each of the 16 rocker nuts an additional ¼ to ½ turn or as recommended by the cam manufacturer. The lifter plungers are now pre-loaded, and the lash should be correctly set. Reinstall the valve covers, clear the tools and start the engine to check results.

Mechanical Tappet Camshafts

Rotate the engine with a crank socket until the No. 1 cylinder’s INTAKE valve fully opens and then just begins to close. Insert a feeler gauge into the lash area of the No. 1 EXHAUST valve. Make note of the feeler gauge size that offers movement in and out, but with slight interference. If it's not at recommended specs, loosen or tighten the rocker nut to gain the recommended clearance. (Log each valve's initial and final lash by cylinder and valve on paper.) \n\nNote: Some rocker arm nuts have an Allen set-screw. This set-screw must be loosened before adjusting the nut to gain proper valve lash, then tightened afterward.

Rotate the crankshaft so that now the No. 1 EXHAUST valve just begins to open. Repeat Step 1 for the No. 1 INTAKE valve, logging the initial adjusted lash accordingly. Repeat for the remaining cylinders and double check that all rocker nuts are secure. Reinstall the valve covers and wires/hoses. Prepare the car for operation and test drive.

Recheck valve lash clearances after several hot/cold/hot operating cycles, carefully checking clearances when the engine is hot. Use the same sequences as above. You may find clearances are wider than initially set (and logged) in your notebook. This is normal at operating temps. Note the differences--if any--and reduce the clearances, if excessive. Adjust the cold-lash values in the log book down by a similar amount they were loose while hot. This permits the correct lashing of valves next time while the engine is not at operating temperatures.

Items you will need

  • Assorted small SAE sockets\n3/8- and 1/2-inch drive socket wrench\nAllen driver or wrench\nFeeler gauges\nRemote starter switch (optional)\nPen and paper