INSPECTING VALVES BEFORE REBUILDING A CYLINDER HEAD
Using a gasket scraper, clean all carbon deposits from valve heads. Follow this by cleaning with a wire brush and solvent. Keep all valves organized so they will be put back in their original locations in the head. Measure valve stem diameters using a micrometer, at about 10mm from the tip, at the midway point and near the bottom of the stem about 10mm from the throat. If a valve shows any variation from the correct diameter at any point, replace the valve. Next, inspect the valve face angle. Grind the valve face just enough to remove any pits and/or carbon deposits. Then, using a caliper, check each valve’s length. Any valve measuring over .003” less than the original valve length should be replaced. Inspect each valve tip for wear. If the valve stem tip shows wear, resurface the tip. Check the valve length again. If it is over .003” less than the original valve length, replace the valve.
Engine Parts Group Technical Committee
with thanks to Toyota Motor Sales, USA (Revised from an article on reconditioning a OHC cylinder head)
August, 2014
