ENGINETNV IDI Service Manual 6-25Cylinder HeadIf distortion exceeds the service limit, resurface orreplace the cylinder head. Remove only enoughmaterial to make the cylinder head flat, but do notremove more than 0.008 in. (0.20 mm).Inspection of Intake and Exhaust ValvesVisually inspect the intake and exhaust valves.Replace any valves that are obviously discolored,heavily pitted or otherwise damaged.Valve Stem DiameterUse a micrometer to measure the valve stemdiameter. Measure the valve stem near thecombustion end and near the opposite end(Figure 6-16, (1)). Record the measurements. SeeIntake / Exhaust Valve and Guide on page 6-5 forthe service limit.Figure 6-16Valve Stem BendPlace the valve stem on a flat inspection block orlayout bed. Roll the valve until a gap can beobserved between a portion of the valve stem andthe surface of the block or bed. Use a feeler gaugeto measure the gap (Figure 6-17). Record themeasurements. See Intake / Exhaust Valve andGuide on page 6-5 for the service limit.Figure 6-17Valve RecessionNote: The valve guides must be installed toperform this check.Insert the valves into their original locations andpress them down until they are fully seated. Use adepth micrometer (Figure 6-18) to measure thedifference between the cylinder head gasketsurface and the combustion surface of eachexhaust and intake valve (Figure 6-19). Record themeasurements. See Cylinder Head on page 6-4 forthe service limit.Figure 6-18Figure 6-190000197(1)00001930001755
