Cylinder head fundamentals
Explain the purpose of a coolant directional nozzle?
A coolant directional nozzle directs the flow of coolant to critical areas of the cylinder head.
What are two advantages of a sodium-cooled valve?
Additional cooling between valve stem and valve guid. Valve head temperature approximately 15% cooler than a solid stem valve.
The most common material used for Diesel engine cylinder head construction is?
Cast iron alloy
Steel head gaskets have high degree of strength, but lack
Conformability
Explain the purpose of cylinder head ports ?
Cylinder head ports direct airflow in and out of the cylinder.
The overhead camshaft design?
Eliminates the need for a push rod.
The purpose of a carbon scaper on a vale is to prevent carbon build up?
In the lower part of the valve guid.
What are two main benefits of a four- valve cylinder head as compared to valve cylinder head?
Increases volumetric efficiency, Increased turbulence,
What are two types of valve guids?
Integral Removable
What are two advantages of using cap screws to retain the cylinder head?
Minimal vertical movement is needed to permit cylinder head removal. Clear access to the cylinder block deck and cylinder/ liner after cylinder head removal.
Valve seals control valve guid and stem lubrication to prevent?
Oil consumption
Depending on the engine design the cylinder head may cover ?
One cylinder, Four cylinder, Six cylinder,
What is two basic functions of valves
Opens and closes the cylinder to allow air flow during the intake and exhaust events. Seal the cylinder during the compression and power events.
A valve spring seat is used to?
Prevent erosion of the cylinder head where the spring contacts the casting.
Explain the purpose of valve spring
Provides the necessary force to keep the valve face in contact with the seat to seal the combustion chamber. They also control valve oscillations and keep the cam follower in contact with the cam lobe as engine rpm increases.
Explain why push rods are most often made of tubular steel?
Push rods are most often made of tubular steel to reduce the weight of the valve operating mechanism.
What are the components of the valve operating mechanism for an engine with the camshaft in the cylinder block?
Rocker arm, Rocker shaft, Support (pedestal) Pushrod, Cam follower, Cam lobe,
What are two benefits of having valves equipped with rotators?
Rotation provide. Changing wear surface for more even valve seat wear. Rotation creates a wiping action that helps keep the valve face and seat clean of carbon.
What is 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.
What are two types of head gasket construction?
Solid steel and composition.
Briefly explain why an exhaust valve is usually made of higher quality material than an intake valve?
The exhaust valve is usually made of higher quality materials than the intake because it operates with higher temperatures and corrosive gases.
Explain the purpose of the hole drilled through the centre of a rocker shaft?
The rocker shaft is hollow or drilled to allow lubrication of the rocker arm assembly.
What are 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 the crankcase. Prevent combustion from leaking past the tube into the cooling system.
Explain the purpose of a valve bridge ( crosshead )?
Used on a four-valve cylinder heads, a valve bridge or crosshead allows one rocker arm to open a pair of intake or exhaust valves simultaneously.
On a solid stem valve, the majority of the cooling takes place between the _____ and the _____.
Valve face Valve seat
Explain the purpose of valve locks?
Valve lock locate and keep the valve spring retainer in position on the valve stem.
Cylinder head retaining studs?
provide higher clamping force than cap screws.
When compare to an integral valve seat, valve seat inserts provide a replicable wear surface with improved?
wear characteristics
