Clean and inspect the cylinder head and valve train components to identify necessary valve service work during engine overhaul. Remove old gasket material from the head gasket, intake and exhaust manifold sealing surfaces. Clean scale from coolant passages and remove deposits from various holes with a wire brush. Clean the cylinder head, lifters, valve springs, spring seats, keepers, and retainers with solvent. Remove deposits from the valves with a motorized wire brush. Inspect the head for cracks, coolant leakage, and damage. Check the head gasket surface for warpage and the valve seats in the combustion chambers. Check valve stem-to-guide clearance and deflection. Inspect each valve face for wear, deformation, cracks, pits, and burned areas. Measure each valve's margin width. Check valve springs for wear and measure their free length. Inspect spring retainers and keepers for wear and cracks. Replace any damaged or excessively worn parts. If valve components are worn beyond limits, reassemble the valves in the cylinder head.