Originally Posted by
Ron
If Rob wasn't burning the midnight oil, I think he might of said-
The journal diameter and a formula is used to determine tolerances (supplied by the engine manufacturer).
For a typical street car:
Cmin = 0.0005 x D
Cmax = 0.001 x D
D = actual journal diameter
You lay a piece across the journal, install the cap (or housing) and torque to specs. Then you remove the cap and match the width of the flattened plastigauge to one of a series of marks on the printed calibrated scale supplied. The clearance indicated by the matching mark must be within Cmin and CMax.
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Miking, or mic'ing, is simply using a micrometer to measure the diameter of the journals. The measurements must be within specs (also supplied by the manufacturer). If the journals are large or used, it is very important to measure each one in several places...
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