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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. 

## Crankshaft 

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 

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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. 

## Checking Alignment 

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. 

