201kb - Cylinder Head Service Flashcards
What are valve springs inspected for?
- Nicks, cracks, corrosion, wear
- Squareness (tilt/lean)
- Tension
- Length
201kb pg. 2
What is spring free length?
Uncompressed spring length
201kb pg. 3
What is spring squareness?
Measurement of the lean in a spring. Maximum allowed variation is generally 1/16”
201kb pg. 3
What does low valve spring tension cause?
- Poor valve sealing
- Poor valve cooling
- Valve float at high engine speeds
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What is valve spring installed height?
Measurement from spring seat on cylinder head to underside of spring retainer.
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How can the valve spring installed height be modified?
Increased by adding shims under the spring. No more than 2 shims with maximum thickness of 0.060”
201kb pg. 14
A vacuum gauge can be used to check valve sealing. What amount of vacuum is used for the test and what constitutes excessive leakage?
Apply 20 inHg
A drop of 10 inHg in 10 seconds is excessive
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Should the cylinder head be pulled down onto the block with the fasteners when reinstalling?
No. Could damage the head or gasket.
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What would result from having oil in the cylinder head bolt holes when installing and torquing the cylinder head down?
Hydraulic lock and potentially crack the block
201kb pg. 17
Accuracy of torquing is subject to what 4 factors?
- Thread condition
- Condition & lubrication of mating surfaces
- Type of lubrication used
- Accuracy of the torque wrench
201kb pg. 18
Valve clearance adjustments are necessary to:
- Provide clearance for heat expansion
- Compensate for regular wear
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What position must the valves be in prior to valve clearance adjustments?
Closed, with cam followers on base circle of cam lobe
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Why must injectors be installed with new o-rings and seals?
To prevent fuel and combustion gas leaks
201kb pg. 23
What could result from over compressing valve springs during installation?
Damage to valve seals
As the installed height of valve springs increase, valve spring tension:
Decreases