How do you adjust valve clearance on 6D14?

To adjust the valve clearance on a 6D14 engine, first, ensure the engine is cold and then remove the valve cover. Rotate the crankshaft to align the timing marks to the top dead center (TDC) for the cylinder you are adjusting. Use a feeler gauge to measure the clearance between the rocker arm and the valve stem, and adjust the clearance by loosening the lock nut and turning the adjustment screw as needed. Finally, recheck the clearance before reassembling the valve cover.