Engine Valve Lash - Inspect and Adjust



Cylinder and valve location
(A) Exhaust valve
(B) Inlet valve

If the valve lash requires adjustment several times in a short period of time, excessive wear exists in a different part of the engine. Find the problem and make necessary repairs in order to prevent more damage to the engine. Not enough valve lash can be the cause of rapid wear of the camshaft and valve lifters. Not enough valve lash can indicate that the seats for the valves are worn. Valves become worn due to the following causes:
• Fuel injection nozzles that operate incorrectly
• Excessive dirt and oil are present on the filters for the inlet air.
• The load capacity of the engine is frequently exceeded.

Too much valve lash can cause broken valve stems, springs, and spring retainers. This will produce emissions in excess of the correct specification. Too much valve lash can be an indication of the following problems:
• Worn camshaft and valve lifters
• Worn rocker arms
• Bent pushrods
• Broken socket on the upper end of a pushrod
• Loose adjustment screw for the valve lash
If the camshaft and valve lifters show rapid wear, look for fuel in the lubrication oil or dirty lubrication oil as a possible cause.

Valve Lash Check
An adjustment is NOT NECESSARY if the measurement of the valve lash is in the acceptable range. Check the valve lash while the engine is stopped. The temperature of the engine does not change the valve lash setting. If the measurement is not within the acceptable clearance, adjustment is necessary.

Valve Lash Adjustment
The No. 1 Cylinder is at the front of the engine.
When the engine is new, the valve lash should be checked and reset after a service interval of 1000 hours.
For example, if the pushrods in a remanufactured engine have been replaced with new parts then Adjust the valve lash to 0.25 ± 0.05 mm (0.0098 ± 0.0020 inch) for the initial rebuild. The tappets should be reset to 0.35 ± 0.05 mm (0.0138 ± 0.0020 inch) at the normal service intervals thereafter.


Setting the valve lash
(A) Angled feeler gauge
(1) Adjustment screw
(2) Locking screw



Remove the valve mechanism cover.  When the valve mechanism cover is removed or installed, the electrical harness must be checked. Do not trap the injector harness when the valve mechanism cover is installed. Do not allow the harness to be in contact with the valve mechanism cover. Renew the harness, if the harness is damaged.
Rotate the crankshaft clockwise until the pair of inlet valves (11) is fully open. Measure the valve lash on inlet valves (9) and exhaust valves (10). If necessary, adjust the valve lash to the settings in Table. Complete the
sequence of checks according to Table until all the cylinders have been checked or adjusted.


Loosen the valve adjustment screw locknut that is on the adjustment screw (1).
Place Tooling between the rocker arm and the valve. Turn the adjustment screw (1) while the valve adjustment screw locknut (2) is being held from turning. Adjust the valve lash until the correct specification is achieved.
After each adjustment, tighten the valve adjustment screw locknut while you hold the valve adjustment screw (1) from turning.


Complete the sequence of checks according to Table until all the cylinders have been checked or adjusted. Reinstall the valve mechanism cover.
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Valve Depth – Inspect


Ensure that the face of the valves are clean. Ensure that the bottom face of the cylinder head is clean. Ensure that the cylinder head is not distorted.
Use the Tooling to check the depths of the inlet valves and the exhaust valves below the face of the cylinder head. 
Measure the depth of the inlet valve and the exhaust valve below the cylinder head face. The minimum and maximum limits for a new engine follow:
Inlet valves
Minimum ...................... 1.40 mm (0.055 inch)
Maximum ..................... 1.70 mm (0.067 inch)

Exhaust valves
Minimum ...................... 1.50 mm (0.059 inch)
Maximum ..................... 1.80 mm (0.071 inch)

Service wear occurs on an engine which has been in operation. If the valve depth below the cylinder head face on a used engine exceeds the specification for service wear, the following components must be replaced.
• Valves
• Valve inserts
Wear limit for inlet valves ... 1.95 mm (0.077 inch)
Wear limit for exhaust valves ................. 2.05 mm (0.081 inch)

Check each valve for cracks. Check the stems of the valves for wear. Ensure that the valves are the correct fit in the valve guides.
Check the load on the valve springs.

Valve Guide - Inspect


Measure the radial movement of the valve in the valve guide.
(1) Valve guide (2) Radial movement of the valve in the valve guide (3) Valve stem (4) Dial indicator (5) Valve head

Place a new valve in the valve guide.
Place a dial indicator with a magnetic base on the face of the cylinder head.
Lift the edge of the valve head to a distance of 15.0 mm (0.60 inch).
Move the valve in a radial direction away from the dial indicator. Make sure that the valve moves away from the dial indicator as far as possible. Position the contact point of the dial indicator on the edge of the valve head. Set the position of the needle of the dial indicator to zero.
Move the valve in a radial direction toward the dial indicator as far as possible. Note the distance of movement which is indicated on the dial indicator. If the distance is greater than the maximum clearance of the valve in the valve guide, replace the valve guide. The maximum clearance for the inlet valve stem in the valve guide with a valve lift of 15.0 mm (0.60 inch) is the following value. ........... 0.08 mm (0.0031 inch)

The maximum clearance for the exhaust valve stem in the valve guide with a valve lift of 15.0 mm (0.60 inch) is the following value. ........... 0.09 mm (0.0035 inch)
The original valve guides are bored into the cylinder head. When new valve guides(1) are installed, new valves and new valve seat inserts must be installed. The cylinder head must be rebored in order to install the new valve guide. Valve guides and valve seat inserts are supplied as an unfinished part. The unfinished valve guides and unfinished valve seat inserts are installed in the cylinder head. Then, the valve guides and valve inserts are cut and reamed in one operation with special tooling.