The clearance between the valve adjuster ball cup and valve stem upper face called valve clearance or tappet clearance. The valve linked with the cam shaft trough push rod and rocker arm. What is really adjusted the clearances between the linked elements.
- Engine stopped
- Turning gear engaged
- Lubrication pump stopped
Checking the Valve Clearance Adjusting Position:
Turn the engine with running gear or turning gear to the compression TDC stroke of the cylinder valve clearance need to adjust. In the flywheel TDC and BDC position is marked.
The cylinders compression TDC position can be checked by removing cam cover and checking inlet and exhaust valve cam position. If the push rod is free of cam lobe, the cylinder is in compression TDC position.
Check the ball cup of the valve adjuster, if the ball cup slightly move then the inlet and exhaust rocker arm is free from cam lobe and is in the position to adjust valve clearance (Fly wheel mark may not show TDC).
Another way to check the position by checking the compressed air flow through the open indicator cock while turning operation. If the compressed air flow cut off, the cylinder is in compression TDC position.
Adjusting Procedure ( MAN B&W Engine):
After positioning the cylinder install two locking screw through the rocker arm bracket to slightly lift up the inlet and exhaust valve operating rocker arm by applying proper torque.
Loose the hexagonal nut and turn the valve adjuster upward with the tools (special tools with torque wrench attachment facility).
Insert the feeler gauge (For thickness check the working instruction of the engine) between ball cup and valve stem top face. Adjust valve adjuster to the position to keep feeler gauge movement should be slightly firm but not tight (Depends upon the engine condition- Cold or Hot).
Hold the valve adjuster in position by tools and tight the hexagonal nut by torque wrench (For torque valve check the working instruction manual of the engine).
Again check the feeler gauge movement because during tightening the hexagonal nut valve adjuster often move.
Remove the locking screw after removing the feeler gauge.
Finally check the ball cup if the ball cup move slightly then the valve clearance adjustment correct.