Page 67 - Mechanic Diesel - TT
P. 67

MECHANIC DIESEL - CITS




           •   Grinding the head

           •   Correct surface finish is very important
           •   Multilayered steel (MLS) gaskets
           •  Require a very smooth surface finish
           •   Head resurfacing

           •  Can increase compression.
           Straightening Cylinder Heads
           Warped aluminum OHC heads
           •   Commonly straightened
           •   Several methods for straightening cylinder heads

           •   Best: heating oven
           •   Straighten the head prior to surfacing
           •   Combustion chamber volumes will remain equal
           Crack Inspection
           •  Cracks are sometimes found:

           •   In combustion chambers
           •   Between adjacent combustion chambers
           •   On the valve spring side of the head
           •  Ways to detect cracks
           •   Magnetic crack inspection

           •   Dye penetrant
           •   Pressure testing
           Crack Repair
           •  Cracks are sometimes repairable

           •   Only practical if the cost of a bare head is more than twice the cost of the crack repair
           •   Cracks in iron heads
           •  Repaired with tapered, threaded plugs
           •   Welding heads
           •   Common method of repairing aluminum head cracks
           Checking Valve Springs

           •  Springs are tested for:
           •   Tension
           •   Squareness
           •   Height

           •  Specifications are available in the service manual
           Checking Valve Stems
           •  Valves wear: oil consumption results
           •   Measure the valve stem with a micrometer





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                                     CITS : Automotive - Mechanic Diesel - Lesson 11 - 14
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