This document provides information about cylinder heads for internal combustion engines. It discusses the functions of cylinder heads, which include sealing the top of the cylinders, forming the combustion chamber, and carrying injectors and valves. It describes different cylinder head designs like overhead camshaft heads, hemispherical heads, and cross-flow heads. It also covers topics like valve guides, valve stem clearances, cylinder head materials, cooling passages, resurfacing, and new technical developments that aim to further reduce weight and increase power density of engines.

1. GOVERNMENT ENGINEERING
COLLEGE,BHUJ
MECHANICAL ENGINEERING
DEPARTMENT
Subject : FICE
Topic : cylinder head
Year : 2018
Prepared by: Kuldip N Thakkar
Guided by : A.S.Sorathiya

2. Cylinder Heads

3. Cylinder Heads
•Cylinder head is a casting that covers the top
of a cylinder.
FUNCTION
•To close tightly / seal off the top of cylinders.
• To form the combustion chamber, together
with the piston crown or in some cases with
the liner itself.
• To carry the injector and the valves

4. Introduction
The cylinder head must be strong and rigid to
distribute the gas forces acting on the head as
uniformly as possible through the engine block. The
combustion gas, the coolant and the lubricating oil
flow independently in the cylinder head and follow
complex three dimensional routes.
Thus cylinder heads are generally produced by gravity
or low-pressure die casting.

5. Cylinder Heads
•Overhead
camshaft heads
will also
incorporate:
•Camshaft(s)
•Rocker arms or
followers

6. Hemispherical Cylinder
Heads
•Hemi – a Chrysler term for a symmetrical cylinder
design.
•Typically valves would be positioned directly
opposite in the head with (ideally) a spark-plug
positioned between them.
• Modern designs my incorporate two spark-plugs.
• NOT exclusive to Chrysler!

8. Hemi Head

9. Cylinder Heads
•Cross flow head
design – the
practice of placing
the intake port and
the exhaust port on
opposite sides of
the cylinder head.

10. Traditional Arrangement
•Traditionally,
combustion
chambers would
have one exhaust
valve and one
intake valve.

11. Multiple Valves
• Four valves per
cylinder – two
exhaust and two
intake valves.
• Pentroof design –
each pair of valves
are inline

12. Intake - Exhaust Ports
• The passageways in the cylinder head
that lead to/from the combustion
area.
• Intake:
• Larger ports = more airflow
• Smaller ports = better velocity for
low RPM operation
• Longer ports = better atomization
on carb and TBI
• Shorter ports = denser A/F charge

13. Gasket Matching
•Using an intake
gasket as a
template to “port”
the heads

14. Coolant Passages
•Coolant travels through the
cylinder head from the
engine block.
•Cylinder head gaskets may
be designed to restrict
coolant flow rate.
• Often a source for corrosion and leakage.

15. Blown Head Gasket•

16. Cylinder Head Removal
• All aluminum cylinder heads
should be removed with a
reverse torque procedure.

17. Cylinder Head Resurfacing
•Heads should be
checked in five places
for warpage, distortion,
bends or twists.
•Check manufacturers
specifications, maximum
tolerances usually
around .004”.

18. Valve Guides
•The “bore” in the
cylinder head that
supports and controls
lateral valve movement.
• Often integral on cast iron
heads
• Always an insert on
aluminum heads

19. Valve Guides
•Steel insert
on aluminum
heads

20. Valve Stem To Guide Clearance
• Always check manufacturers specs
• Intake valve will typically be .001 to .003”
• Exhaust valve will typically be .002 to .004”
• The exhaust valve stem clearance will generally be greater
due to the higher operating temperatures.

21. Valve Guide Wear
•Guides are
checked in 3
locations
• With a small-hole gauge
then measured with a
micrometer
• Or checked with a small
bore gauge

22. Valve Stem To Guide Clearance Correction
•Valve Guide Inserts –
(integral) the old guide
is drilled oversized and
inserts are installed.
•Pressed fit
•May be steel or bronze

23. Cylinder head material
As a result of the permanent increase of combustion
pressures and temperatures, the potential of the
common aluminium cylinder head alloys is almost
fully exploited.
In order to satisfy all the product requirements,
optimised casting alloys and a proper control of the
as-cast microstructure by the application of
sophisticated casting processes are generally

24. Strength
The applied aluminium alloys have to offer sufficient
strength and hardness at room temperature for
machining and assembly.
Furthermore, high strength at elevated temperatures
(up to 250°C) is crucial to ensure that the engine
block-cylinder head assembly can withstand the
combustion forces and the forces resulting from
thermal expansion and contraction during service
cycles without losing tightness of the cylinder head
gasket.
Creep strength is required in particular for the head
gasket area

25. Thermal conductivity
The cylinder head can support the high combustion
temperatures only due to an efficient cooling. A
decisive characteristic for the cylinder head material is
therefore a high thermal conductivity.
On the other hand, any addition of alloying elements
to aluminium for the purpose of increasing strength or
creep resistance results in a decrease of the thermal
conductivity.
Hence, a compromise between the two counteracting
targets has to be found.

26. Surface quality
An unimpeded flow of the incoming gas is of major
importance for the combustion process. Thus, high
demands are made on the smoothness of the surface of
inlet and outlet channels.
The roughness of the flame deck surface should be
minimized as well, because any notches can lead to
the initiation of fatigue cracks.

27. Castability
• The castability of an alloy is
generally improved with increased
Si content, while Cu additions,
which are required for high
temperature strength, have a
negative effect on the feeding
behaviour. Insufficient feeding
could lead to defects in the as-cast
structure, in particular porosity.
The presence of such defects
would be critical in those regions
of the cylinder head which are
exposed to high cycle

28. Design features
Conventional engines with an „in-line" array of the
cylinders have one cylinder head. V-engines generally
need two cylinder heads, which may have identical or
differing geometry.
Provided that the angle between the two cylinder axis
planes is not too big (<= 15°), V-engines can also be
equipped with only one cylinder head. In this case, the
cylinder axis is not perpendicular to the joint face

29. Cylinder head with individual throttle
bodies and exhaust manifolds

30. New technical development
• Enable further weight reduction
• Permit increased power densities; future expected
performance values are up to 65 kW/l for direct
injection diesel engines and up to 75 kW/l for
boosted gasoline direct injection engines
• Allow the introduction of advanced combustion
systems for both spark (SI) and compression (CI)
ignition engines.
• In the next generation engines, the combustion
pressure is expected to rise to the 180-200 bar
range for CI engines and to 100-120 bar range for
boosted SI engines.

31. Thank you