Face of valve must run true with stem within 0.0015-inch Valve face. Do not include when measuring thickness A A Figure 10-7.  Valve showing locations for checking runout and  section for measuring edge thickness. Figure 10-9.  Valve spring compression tester.  Figure 10-8.  Checking valve stretch with a manufacturer’s gauge.  indicator, measure the shaft runout. If the total indicator  reading exceeds the dimensions given in the manufacturer‘s  table of limits, the shaft must not be re-used. A bent crankshaft  should not be straightened. Any attempt to do so results in  rupture of the nitrided surface of the bearing journals, a  condition that causes eventual failure of the crankshaft.  Measure the outside diameter of the crankshaft main and rod- bearing journals using a micrometer.  [Figure 10-11]  Internal  measurements can be made by using telescoping gauges, and  then measuring the telescoping gauge with a micrometer.  [Figure 10-12]  Compare the resulting measurements with  those in the table of limits. Inspect the shaft’s diameter for correct size with a  micrometer. Rocker shafts are often found to be scored and  burned because of excessive turning in the cylinder head.  Also, there may be some pickup on the shaft (bronze from  the rocker bushing transferred to the steel shaft). Generally,  this is caused by overheating and too little clearance between  shaft and bushing. The clearance between the shaft and the  bushing is most important.  Use extreme care in inspecting and checking the crankshaft  for straightness. Place the crankshaft in V-blocks, supported  at the locations specified in the applicable engine overhaul  manual as in  Figure 10-10.  Using a surface plate and a dial  Check bushings that have been replaced to determine if the  bushing and rod bores are square and parallel to each other.  The alignment of a connecting rod can be checked several  ways. One method requires a push fit arbor for each end of  the connecting rod, a surface plate, and two parallel blocks  of equal height. 10-10 Checking Alignment Crankshaft