CYLINDER HEADS
What are the three things a cylinder head gasket must seal?
Combustion pressure, coolant passages, and oil passages.
What component supports and aligns the valve stem as the valve moves?
The valve guide.
What is the main job of a valve spring?
To close the valve and maintain valvetrain control.
What engine component controls when the intake and exhaust valves open and close?
The camshaft.
How many times does the crankshaft rotate for each camshaft revolution in a four-stroke engine?
Two crankshaft revolutions.
What measuring tools are commonly used to check cylinder head deck flatness?
A precision straightedge and feeler gauges.
What two pieces of information must be compared to determine whether a valve stem passes its dimensional inspection?
The actual valve stem diameter and the OEM diameter specification or service limit.
What tool is used to measure valve spring force at a specified compressed height?
A valve spring pressure tester.
When the OEM specifies measuring cam lift from lobe dimensions, what is the calculation?
Maximum lobe height minus base-circle diameter.
What does it mean when an engine is described as an interference engine?
Incorrect valve timing can allow the pistons and valves to contact.
What does it mean when cylinder head warpage exceeds the manufacturer's maximum specification?
The head fails inspection and needs further evaluation or corrective service before reuse.
What problem can result from excessive valve stem-to-guide clearance?
Excessive valve movement, poor sealing, or increased oil consumption.
A valve spring passes its free-length measurement but fails its pressure test. Does it pass inspection?
No. It fails because its measured force is below the OEM specification.
What does a camshaft runout measurement help determine?
Whether the camshaft is bent or outside its allowable straightness limit.
What does a VVT cam phaser change?
The camshaft's timing relative to the crankshaft.
Why must a technician check minimum cylinder head height before resurfacing?
To ensure removing material will not make the head thinner than the manufacturer's service limit.
A valve stem measures within specification, but stem-to-guide clearance is excessive. What other component may be worn?
The valve guide.
What problem can a bent pushrod cause in an OHV engine?
Incorrect valve motion or reduced effective valve lift.
A camshaft journal meets its diameter specification, but oil clearance is excessive. What should be inspected next?
The mating bearing or cylinder head journal bore.
Why must cylinder head bolts be tightened in the manufacturer's specified sequence and stages?
To apply the required clamping force evenly and avoid distortion or sealing problems.
A head passes its flatness check but has deep corrosion around a coolant passage. Can it automatically be approved for reassembly? Why?
No. The corrosion must also be evaluated because flatness alone does not establish serviceability.
A valve seat is severely pitted, but the valve stem measures within specification. Why can't the valve assembly automatically be approved?
Because the damaged seat may prevent proper sealing and requires evaluation or repair.
Why must a technician follow the manufacturer's procedure when installing hydraulic lash adjusters?
Because they may have specific preparation, positioning, or installation requirements; they should not automatically be adjusted like solid lifters.
Why can an overhead-cam cylinder head with badly worn camshaft bearing saddles be difficult to repair?
Because the saddles may be machined into the head and caps, rather than using individually replaceable bearings.
After timing installation, the engine becomes unusually difficult to turn by hand. What should the technician do?
Stop rotating it and investigate the cause using the OEM procedure. Do not force it.