J- Cylinder Head Fundamentals
Explain the purpose of cylinder head ports
Direct airflow in and out of the cylinder
Explain the purpose of a coolant directional nozzle
Direct coolant flow to critical areas of the cylinder head
List two types of valve guides
Integral and Removable
Explain the purpose of a valve bridge (crosshead)
It spans a pair of intake or exhaust valves and allows one rocker arm to open both valves simultaneously
A valve spring seat is used to
Prevent erosion of the cylinder head where the spring contacts the casting
Explain the purpose of a valve spring
Provide the necessary force to keep the valve face in contact with the seat to seal the combustion chamber. Also controls valve oscillations and keep the cam follower in contact with the cam lobe as engine RPM increases
List two reasons why there must be a seal between the cylinder head and an injector tube
To prevent coolant from leaking past the tube into the combustion chamber and crankcase, and combustion from leaking past the tube into the cooling system
list the two advantages of a sodium-cooled valve
additional cooling between valve stem and valve guide and 15% cooler than a solid stem valve
List two advantages of using cap screws to retain the cylinder head
an efficient method for the installation and removal of cylinder heads, and clear access to the cylinder block deck and cylinder liner after cylinder head removal
Depending on engine design the cylinder head may cover
any amount of cylinders
The most common material used for diesel engine cylinder head construction is:
cast iron alloy
Steel head gaskets have a high degree of strength but lack (blank)
conformability
The overhead camshaft design
eliminates the need for a pushrod
The purpose of a carbon scraper on a valve it to prevent carbon buildup
in the lower part of the valve guide
briefly explain why an exhaust valve is usually made of higher quality material than an intake valve
it operates with higher temperatures and corrosive gases
valve seals control valve guide and stem lubrication to prevent:
oil consumption
List the two benefits of having valves equipped with rotators
provides a changing wear surface for more even valve/seat wear and creates a wiping action that helps keep the valve face and seat clean of carbon
List the components of the valve operating mechanism for an engine with camshaft in the cylinder block
rocker shaft, rocker arm, support (pedestal) push rod, cam follower, cam lobe
The purpose of the coolant and oil passages in the cylinder head is to
route coolant and oil to the cylinder head and its components
List the two basic functions of valves
seal the cylinder during compression and power events and open and close the cylinder to allow airflow during the intake and exhaust events
List two types of head gasket construction
steel and compositionk
Explain the purpose of valve locks
they locate the retainer during assembly and keep it in position
What is true about cylinder head retaining studs?
they provide a higher clamping force than cap screws
Explain the purpose of the hole drilled through the centre of a rocker shaft
to allow lubrication of the rocker arm assembly
Explain why pushrods are most often made of tubular steel
to reduce the weight of the operating mechanism
On a solid stem valve, the majority of cooling takes place between the (blank) and the (blank)
valve face and valve seat
list the two main benefits of a four-valve cylinder head (as compared to a two-valve cylinder head)
volumetric efficiency and turbulence
When compared to an integral valve seat, valve seat inserts provide a replaceable wear surface with improved:
wear characteristics and heat resistance