Page 67 - Mechanic Diesel - TT

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