To take off the valve cover(s), turn out first by increments the rocker arm shaft bolts using the outer bolts first. In case of the rocker arms are separated or isolated from the shaft, it would be wise to jot down the orientation. Then, pull out the pushrods and then set them aside so that they do not mix up during instillation, in a box that confines the pushrods. Check the rocker arm for wear, cracks and signs of damage on the contact area with the pushrods and at the valve stems and at the pivot area and at the shaft where the part creating the rocker arm replace worn or damaged part. Check that the hole at the pushrod end of each rocker arm is open and after that inspect the pushrods for the cracks and other signs of heavy wear, roll each over the flat surface, to check their bend. To reinstall, coat the lower end of each pushrod lightly with clean engine oil or moly-base grease, then return each one to its former position, being certain that it makes bottom in the lifter socket. Moly-base grease shall be put on the ends of the valve stem and the upper end of the push rod as well as at the rocker arm shaft. The rocker arms are then placed on the shaft and the assembly is lowered onto the cylinder head screws the bolts progressively from the middle and then outwards to the required torque, the pushrods should fit into the appropriate holes on the rocker arms. Let the engine to idle for 20 minutes before turning on, and last step you need to install the valve covers.