How do you adjust 8dc9 tappet clearance?

To adjust the tappet clearance on an 8DC9 engine, first, ensure the engine is cold for accurate measurements. Remove the valve cover to access the tappets, then use a feeler gauge to measure the clearance between the tappet and the valve stem. Adjust the clearance by loosening the locknut and turning the adjusting screw until the specified gap is achieved, then re-tighten the locknut. Repeat for each valve, ensuring proper clearance is maintained for optimal engine performance.