6-Cylinder Engin Valve Lash Adjustment Method

Valve clearance affects the performance of 6-cylinder engin. Too little clearance leads to poor valve closure, power loss, and valve erosion; too much clearance produces rattling, accelerated wear, and reduced power. Regular inspection and adjustment is necessary maintenance.

1. Adjustment preparation

Engine status: must be completely cooled (room temperature). Measurement is inaccurate when hot.

Position piston: Turn first cylinder piston to compression upper stop. Refer to crankshaft pulley or flywheel mark. Camshaft cams should be backed off the valves.

Tools: plug ruler, wrench, screwdriver, socket wrench, service manual (check standard values).

2. Standard Adjustment Method (Manual Adjustment Screws)

Checking Current Clearance: Select the corresponding valve and insert a plug rule of specified thickness between the rocker arm and the top of the valve stem. There should be slight resistance to pumping the plug rule but it can slide. Too loose or too tight needs to be adjusted.

Loosen the lock nut: Hold the adjusting screw with a wrench and loosen the lock nut (usually 14mm or 17mm) with another wrench.

Adjusting the gap: Turn the adjusting screw (clockwise to increase, counterclockwise to decrease), while using a plug ruler to detect to the specified value and a slight resistance. Keep the screw immobile.

Lock nut: Tighten the lock nut. Re-test the gap again with the plug gauge, deviation needs to be re-adjusted.

Adjust in order:

① Adjust the adjustable valve at the compression top stop of the first cylinder.

② Rotate the crankshaft 360 degrees to the next cylinder compression stop, adjust the position of the adjustable valve.

③Repeat until all valves are adjusted.

3. Other adjustment methods

Shim adjustment type: Measure the current gap and calculate the required shim thickness (new shim thickness = old shim thickness + (measured gap - standard gap)). Remove the old shim by pressing down the rocker arm with a tool and install the new shim.

Hydraulic tappet: No need to manually adjust, automatic compensation by oil pressure. The hydraulic tappet: No manual adjustment is required, it compensates automatically by oil pressure.

4. Key Notes

Strictly operate the vehicle cold. Operate according to the manual sequence and standard values. Intake and exhaust valve clearances are usually different.

Lock nut torque is up to standard. Too loose will loosen, too tight will damage the threads.

Clearance must be rechecked after adjustment. Locking is the main cause of variation. Keep clean to prevent dust ingress.

5. Verify after adjustment

Start the 6-cylinder engin, listen for abnormal knocking in the valve area, and observe if the idle speed is smooth.

Valve lash adjustment is fine operation. According to the standard process, cold condition, the correct tools and strict re-testing, can ensure smooth and efficient engine operation and prolong life. Unskilled operators are advised to seek professional maintenance.