The document discusses various aspects of engine cylinders, including: - Cylinder arrangements can include inline, V-shaped, or opposing rows. Modern engines often use V-shaped cylinder arrangements. - The cylinder block forms the foundation of the engine and houses the cylinders. It typically includes integrated cooling passages and galleries for oil distribution. - Key parts of the cylinder block include the cylinders themselves, cylinder head mounting areas, crankcase, and passages for fluids like coolant and oil. Cylinder blocks are usually made of gray cast iron or aluminum alloys. - The cylinder head covers the top of the cylinders. It contains valves, spark plugs, and passages for air and fluids. Cyl

1. Engine: Location of engine
114

2. Cylinder arrangement
• Construction details
• Cylinder block
• Cylinder head
• Cylinder liners
• Piston
• Piston rings
• Piston pin
• Connecting rod
• Crankshaft
• Valves
115

3. Cylinder arrangement
• Three, four, five, six, eight and twelve cylinders are used in car
engines.
• Buses and trucks use twelve and sixteen cylinder engines.
• The engine cylinders can be arranged in the following
ways
(a) In a row (in-line)
(b) In two rows or banks set at an angle (V-type)
(c) In two rows, opposing each other (flat, or pancake)
116

4. Cylinder arrangement
117

5. Cylinder arrangement: Construction details
• The cylinder of the internal combustion engine is the working
chamber of the volumetric displacement. During engine operation,
the internal and external parts of the cylinders experience different
heating.
• The inside part of the cylinder is a sleeve or cylinder liner.
• The outer part of cylinder is the motor cooling jacket.
118

6. a – without cylinder liner, but with short insert;
b, c – with wet cylinder liner;
d – with wet cylinder liner and short insert;
1 – Cylinder block;
2 – motor cooling jacket;
3 – insert;
4 – cylinder liner;
5 – seal rings;
6 – anti-cavitation ring.
119

7. What is Cylinder Block?
• An engine block is a structure that contains cylinders, and other parts of
an internal combustion engine.
• In old engines, the engine block has only the cylinder block, to which a
separate crankcase was attached.
• In modern engines, the engine block consists of the crankcase integrated
with the cylinder block as a single component, giving a rigid structure.
• Engine blocks also often include elements such as coolant passages and
oil galleries.
120

8. Cylinder Block
• The cylinder block, cylinder head, and crankcase are the three parts that
form the foundation and main stationary body of an automobile engine.
• They serve as support an enclosure for moving parts.
• The cylinder block may also have a separate crankcase for the crankshaft,
which is limited to larger engines, marine, and stationary engines.
• A separate aluminum crankcase would result in saving weight as well as
enable cheaper and quicker replacement.
121

9. Parts of Cylinder Block
1. Cylinders
2. Oil passages and galleries
3. Deck
4. Crankcase
5. Head studs
6. Core plugs
7. Water pump mounting
8. Oil filter
122

10. 123

11. 1. Cylinders : Cylinders are the parts in which the movement of the piston takes
place. They are generally made of large size and have holes to form a seal with
the piston. The number of cylinders holds the power and size of the engine.
2. Oil Passages and Galleries: These are essential components of the cylinder
block for lubrication purposes. These provide oil to reach the cylinder head and
crankshaft.
3. Deck : This is the top surface of the block where the end of the cylinder
remains.
4. Crankcase: This component houses the crankshaft and is found under the
modern engine block.
5. Head Studs: These are typically manufactured from a round rod of alloy steel.
Threads are applied at both ends. This allows a tighter fit in the block, which
prevents the stud from loosening when the stud nut is removed.
6. Core Plugs : A core plug is a cap of the engine block at the end of a coolant
passage, which is used to prevent leakage of water or coolant from the engine.
7. Water Pump Mounting : A water pump is provided on the side of a cylinder
block in housing coupled with a coolant casing.
8. Oil Filter : It is typically located either on the flank or under the engine block.
There is an oil filter that keeps as many contaminants out of the lubricant that
circulates the engine.
124

12. Material Used in Cylinder Block
• The cylinder block is usually made from gray cast iron, and sometimes with the
addition of nickel and chromium.
• Some blocks are cast from aluminum, in which cast iron or steel sleeves are used.
• For most engines, cast iron has been found to be a satisfactory cylinder wall material,
as it has better wearing qualities.
• In some small engines, the cylinder walls are placed with chromium, a very hard metal,
to reduce wall wear and to increase their service life.
• Tests are being carried out on high silicon-aluminum alloys to determine their
possibilities as a material for cylinder block and crankcases. These alloys have a low
coefficient of thermal expansion and high wear resistance. 125

13. Functions of Cylinder Block
• The L-head engine blocks contain openings for the valves and valve ports.
• The bottom of the block also supports the crankshaft and oil pan.
• On most engines, the camshaft is supported in the cylinder block by bushing that fits
into machined holes in the block.
• In L-head inline engine, the intake and exhaust manifolds are connected to the side of
the cylinder block.
• On I-head engines the manifolds are joined to the cylinder head. Other parts attached
to the block include the water pump (at the front), timing gear or timing chain cover (at
the front), flywheel and clutch housing (at rear), ignition distribution, and fuel pump.
126

14. Types of Cylinder Block
• Engine blocks are classified according to the size of the engine
cylinders.
1. V-engine cylinder
2. Inline cylinder
3. Opposed engine or Boxer engine cylinder
127

15. V-engine Cylinder
• This is the modern engine cylinder
and is widely used nowadays.
• In this configuration, the engines are
provided in two rows.
• These two rows are placed at an
angle to each other.
• The angle V is kept between 15° to
20°, as a larger angle makes it more
difficult to balance the engine.
• These are difficult to balance with
the counterweight on the crankshaft.
• There are different types of v
engines, V16s, V8s for heavy
vehicles, and V4s for small
motorcycles are used as cylinder
blocks.
128

16. Inline Cylinder
• An inline engine is a
type of cylinder block,
in which a series of
cylinders are arranged
in such a way that they
run in a single line.
• Vehicles with this type
of cylinder block
operate smoothly.
• They are mostly used
where high rpm is
needed.
• It is often used
in passenger cars.
129

17. Opposed Engine or Boxer Engine Cylinder
• The Boxer engine is a flat pressed
V engine.
• In this engine cylinder, the blocks
coming in two rows of two
cylinders are set as opposed to
each other.
• They are also known for pancake
engines.
• They require very little headroom
as the engine compartment can be
very small.
• These are commonly seen on 4
cylinder Volkswagen engines.
• In addition, they are also
employed on Porsche and Subaru
and some other high-speed
engines.
130

18. Problems of Cylinder Block
• When cylinder blocks continue to operate, they sometimes break or
wear out.
• what are the problems that make them worse.
1.Leakage of external engine coolant
2.Worn or cracked cylinder
3.Porous engine block
131

19. 1. Leakage of External Engine Coolant: This leak could be from the
water pump, radiator, heater core, or a loose hose. Sometimes it can
also be due to engine block because of cracks.
1. Worn or Cracked Cylinder: After the cylinder has been in
operation for a long time, wear inside the cylinder is a common
problem. This can damage the smooth machined wall and affects the
sealing by piston rings. It can be avoided by increasing the bore size.
1. Porous Engine Block: This is usually caused by contaminants that
enter the metal. This often happens while the manufacturing process
is going on. You can’t avoid this problem because that’s where the
cylinder block originated.
132

20. Cylinder head
What is a Cylinder Head?
• A cylinder head is the cast metal part that covers the top part of a
cylinder.
• The cylinder head mounts on the cylinder block or engine housing.
133

21. 134

22. Cylinder Head Function
• What is the function of cylinder heads in car engines?
• Provide the mounting structure for various components such as the inlet and outlet
exhaust valves and ducts, spark plugs, injectors, and (in some head designs), the
camshaft.
• Contain the passages for coolant, oil, and combustion gases
• Dissipate the heat produced by the engine and, therefore, produce cooling
• Act as the combustion chamber seal and the engine’s mechanical control
powerhouse
• Take the compression resulting from combustion pressure
135

23. • A cylinder head contains intake air, exhaust, Copland, and oil
passageways.
• One of the functions of a cylinder head is cooling the engine. The head
achieves that using two main methods; water or air.
• Water-cooled heads are the most popular, and many modern engines
are of this type.
• Air-cooled cylinder heads use large fins that fan the air to bring
about cooling.
136

24. Cylinder Head Materials and Manufacturing
• Auto cylinder heads are cast from molten metal.
• Usually, manufacturers use the LFC , lost-foam casting, for the cylinder head casting.
• The method uses polystyrene foam to produce the required pattern.
• Cylinder heads can be made from iron or aluminum.
• It depends on the required performance, durability, and other factors. Each material offers
specific advantages that suit particular situations.
• Aluminum cylinder heads
• Iron cylinder heads
137

25. Aluminum cylinder head
Iron cylinder heads-
138

26. Aluminum cylinder heads-
• Aluminum produces lightweight heads that also dissipate heat more
efficiently.
• They give better fuel economy and heat transfer, aluminum heads are
often used in performance and race cars.
• In these cars, weight saving and rapid engine cooling are necessary
features.
• Most gasoline engines use aluminum cylinder heads.
139

27. Iron cylinder heads-
• Iron cylinder heads are less expensive than those made from
aluminum.
• They are also high-strength and durable.
• Iron heads also transfer heat poorly and do not fit demanding
applications such as race cars.
140Slide 115: Cylinder arrangement

28. Cylinder arrangement - Cylinder liners
• Cylinder liners are casting from high strength cast iron or special
steels.
• Sometimes aluminum cylinder liners are plating with chrome.
141

29. Cylinder Liner Defects
The cylinder liners wear out due to friction between the piston and the mirror
(inner cylinder wall).
As a rule, increased wear may occur by the following reasons:
– Not enough motor oil on the cylinder liners walls;
- Engine did not work for a long time, and all the motor oil was drained in the
crankcase;
– Use of inappropriate viscosity motor oil;
– The main causing of corrosion is use of water as a coolant;
– Chips and scratches occur due to improper installation, dismantling (all actions for
shooting cylinder liners must be carried out according to the rules with a special
puller);
– The engine is not used correctly.
Slide 115: Cylinder arrangement142

30. Piston
• A piston of an internal combustion engine is
in the form of an inverted bucket shape and
it is free to slide in the cylinder barrel.
• The gas tightness is secured by means of
flexible piston rings, which are in the
grooves of the piston.
• These grooves are cut in the upper part of
the piston.
143

31. Functions of Piston
1. It forms a moveable wall of the combustion chamber.
2. It transmits turning force to the crankshaft via the connecting rod.
3. It functions like a crosshead and transmits side thrust, which is due
to the angularity of the connecting rods, to the cylinder walls.
144

32. Qualities and Requirements of Piston
1. It must be strong enough to withstand high pressure caused due to the
combustion of fuel.
2. It must be very light in weight to have minimum primary and secondary
forces, which are caused due to the inertia forces of the reciprocating
masses. A light piston permits higher speed of the crank.
3. The piston material must be a good conductor of heat so that detonation is
suppressed, and higher compression ratio is possible to get fuel economy.
4. The piston operation must not be noisy.
5. The piston must be of less coefficient of expansion.
145

33. Piston Temperatures at Various Stages
• It has been found by experiments that
the maximum temperature produced is
in the centre of the piston head, and the
temperature decreases towards the edge
of the piston head, and also decreases
rapidly down side of the piston.
• Most of the heat is passed into the
cylinder block at the ring belt, and some
temperature drop takes place from the
skirt.
146Slide 115: Cylinder arrangement

34. PISTON RINGS
• Piston rings are those rings which are fitted in
the grooves provided in pistons
• Piston rings are the ones that completely seal out
the cavity formed between the piston and
cylinder
• Piston rings are not completely closed and are
provided with a gap at the ends.
• The gap allows the rings to fit over the piston
and lets the rings expand without breaking.
When the piston and piston rings expand with
excessive heat, the ring gap becomes smaller
147

35. Types and Forms of Piston rings
• Generally, there are two forms of gaps provided in piston rings:
(a) straight or normal gap
(b) diagonal or scarf gap
• Two types of piston rings are widely used:
1. Compression ring
2. Oil control ring
The compression ring serves two purposes, viz.
(i) to seal the combustion chamber and
(ii) to provide a path for heat transfer from the piston to the cylinder walls. This
provides effective cooling.
148

36. 149

37. 150

38. 151

39. • The groove or slot cut on
the circumference of the
oil ring is also shown
clearly.
• Radial holes are drilled in
the oil ring so that oil
collected in the ring
groove can pass in the
piston ring groove.
152

40. 153

41. 154

42. Functions of Piston Rings
1. The piston rings seal the passage inside the cylinder
1. They provide a path for conducting heat from the piston head to the
cylinder walls.
1. Piston rings scrap the excess oil from the cylinder walls and only a
thin film of oil is left to lubricate the piston rings.
155

43. Piston Ring Joints
• The oil control and compression rings usually butt together with a
joint called a butt gap.
• In a two-stroke cycle engine, the ends of the rotating ring could move
into a cylinder part and cause breakage.
• Most two-stroke cycle pistons therefore, have a pin in the piston
groove that prevents the ring from rotating.
156

44. 157

45. 158

46. PISTON PIN
• A piston pin is also known as a wrist pin because of its similarity in
construction with human hand and arm joint.
• A piston pin is a link for connecting the piston and the connecting
rods.
• The piston pin is fitted in the bosses which are in the piston.
• The small end of the connecting rod is accommodated in between the
piston bosses.
159

47. Piston Pins
• These pins can withstand
high temperature, heavy
loads, and bending force.
160

48. 161

49. • The ends of the circlip ring
are pressed and inserted in
the piston boss, and then
released in the groove made
for this ring.
• Piston pins are made of
casehardening steel, either
plain carbon steel, nickel
steel or chrome-nickel steel.
• The pins are designed to
work as bearing journals.
162

50. Types of Piston Pins
• Types of pins incorporated in pistons used in engines.
1. fixed pin,
2. full-floating pin and
3. semi-floating pin.
• The fixed or anchored pin connects the piston with a screw running through
one of the bosses while the linking rod vacillates on the pin.
• Full floating pin rotates inside the connecting rod and the bosses whereas
the semi-floating pin is fixed to the linking rod and turn in the bosses
eventually.
163

51. Connecting Rod
164

52. Connecting Rod
• The connecting rod is a connection between the piston and a crankshaft.
• The small end of the connecting rod is connected to the piston pin and
the big end to the crank pin.
• The purpose of the connecting rod is to convert the linear motion of the
piston into the rotary motion of the crankshaft.
• A connecting rod with a tension load is made of forged steel, cast steel, or
fabricated steel.
• Rods with a compression loading are cast nodular steel or aluminum alloy.165

53. Connecting Rod
• The connecting rod consists of an I-beam cross-section and is made of
forged steel.
• Aluminum alloy is also used for connecting rods.
• The lighter the connecting rod and piston, the greater the resulting in power
and the lesser the vibration because the reciprocating weight is less.
• The connecting rod carries the power thrust from piston to the crankpin and
hence it must be very strong, rigid and also as light as possible.
166

54. Parts of Connecting Rod
1. Small End
2. Big End
3. Bushing
4. Bearing inserts
5. Bolt and Nut
6. Shank
7. Wrist pin or Gudgeon pin
8. Piston
9. Bearing cap
167

55. 1. Small End
• The end at which the connecting rod is attached to the face of the
piston pin is known as the small end of the connecting rod.
2. Big End
• The end at which the connecting rod is attached to the side of the
crank pin is known as big end of the connecting rod.
168

56. 3. Bush Bearing
• Both ends of the connecting rod are fixed with a bush bearing. A phosphor
bronze bush is fitted with the solid eye is attached to the small end of the
connecting rod.
• The Big end is attached to the crankpin. The end is divided into two parts
and is supported over the crank bearing shell.
4. Bearing Insert
• In the big end of the connecting rod, there is a bearing insert that is
connected to the bearing cap, it is known as a bearing insert. These are
made in two parts that fit together on the crankshaft. This is the position
where the connecting rod travels along the reverse direction.
169

57. 5. Bolt and Nut
• After the connecting rod is fitted with the crank at the bottom, both sides of
the big ends are fastened by some bolts and nuts. Thus, by combining these
all components the connecting rod is ready to use.
6. Shank
• Furthermore, each of the bolt and nuts are employed to connect both the
connecting rod and bearing cap. And a section beam is applied it is known
as shank. The section of the rod may be rectangular, tubular, and a circular
section.
• The connecting rod length lies on the ratio of (l/r)
Where,
I = is the length of the shank or beam
r = is the radius of the shank.
170

58. 7. Wrist Pin or Gudgeon pin
• The engine piston is connected to the connecting rod with the help of a
hollow hardened steel tube called wrist pin. It is also known as
gudgeon pin. Wrist pin goes through the short end of the connecting
rod and pivots on the engaged piston.
8. Piston
• The piston is connected to the crankshaft with the help of a connecting
rod, which is usually shortened to the rod or Conrod. The purpose of
the piston is to work as a movable plug in the cylinder, which forms
the bottom of the combustion chamber.
9. Bearing Cap
• Shell bearings have an adjustment for wear, but it controls the running
and the side clearance allows the bearing cap to be tightened correctly.
171

59. Construction and Functions of Connecting Rod
• There are two types of ends small end
and big end bearings.
• The big end is split at right angles to
its length as at (a) or at an angle as at
(b), in order that it may be assembled
on the crankpin.
• Modern engines do not have bearing
metal fused to the bore of a big end,
but it uses separate low carbon steel
bearing shells.
172

60. Construction and Functions of Connecting Rod
• The small end is usually a solid eye fitted with a phosphor bronze
bush and a screw to close the eye around the pin.
• All the connecting rods in an engine must be of equal weight
otherwise noticeable vibration may occur.
• In the assembly, the connecting rods and caps are individually
matched to each other.
173

61. Types of Connecting Rod
1. Plain type rod
2. Fork and blade rod
3. Master and slave rod
4. Billet conrods
5. Cast rods
6. Forged rods
7. Powered metal conrods
174

62. 1. Plain Type Rods
• The plain type of connecting rod is used in inline and
opposed engines.
• The big end of the connecting rod is attached to the
crankpin and fitted with a bearing cap.
• The bearing cap is mounted by a bolt or stud at the end
of the connecting rod.
• The connecting rod must be replaced in the same
cylinder and in the same relative position to maintain
proper fit and balance.
175

63. 2. Fork and Blade Rods
• These types of connecting rod are used on V-twin motorcycle
engines and V12 aircraft engines.
• In each pair of engine cylinders, a “fork” rod is divided into two
parts at the big end and a “blade” rod is tapered from the opposing
cylinder to fit this gap in the fork.
• This system eliminates the rocking couple that occurs when the
cylinder pairs are balanced along with the crankshaft.
• In the big-end bearings type of arrangement, the fork rod has a single
wide-bearing sleeve that extends over the entire width of the rod,
including the central gap.
• The blade rod then runs directly outside this sleeve, not on the
crankpin. This causes the two rods to move back and forth, this
reducing the force on the bearing and the surface speed. But, the
bearing speed also reciprocates instead of continuously rotating,
which is a major problem for lubrication. 176

64. 3. Master and Slave Rods
• Radial engines typically use master-and-slave
connecting rods.
• In this system, the one piston consists of a master rod
with a direct attachment to the crankshaft. Other
pistons connect their connecting rods to the rings
surrounding the edge of the master rod.
• The disadvantage of master-slave rods is that the
stroke of the slave piston is slightly larger than that of
the master piston, which increases the vibration in the
V-type engine.
177

65. 4. Billet rods
• Billet connecting rods are designed from steel or
aluminum.
• Compared to other types of connecting rod, they are
lighter, stronger, and longer in lifespan.
• It is commonly used in high-speed vehicles.
• It is sometimes designed to reduce stress risers and
ease into the natural grain of the billet material.
178

66. 5. Cast Rods
• These types of connecting rod are preferred and
designed by manufacturers because they can
capable of handling the load of a stock engine.
• Cast rods require low cost to produce and cannot be
used in applications of high horsepower.
• The cast rods have a noticeable seam in the middle
that separates them from the forged type.
179

67. 6. Forged Rods
• These types of connecting rod made by forcing
a grain of material to the shape of the end.
• Depending on the required properties the
material may be steel alloy or aluminum.
• Commonly used steel alloys are chrome and
nickel alloy to increase the strength of the
connecting rod.
180

68. 7. Powered Metal Conrods
• It is prepared with a metal powder mixture that is
pressed into the mould and heated to a high
temperature. This mixture made into a solid form.
• It may require light machining but the product
basically comes out of a finished product mould.
• Conrods of powder metal are less costly than steel
and they are stronger than cast rods.
181

69. Faults of Connecting Rods
• Following are the faults of a connecting
rod:
1. Fatigue
2. Hydrolock
3. Over revving
4. Pin failure
182

70. 1. Fatigue
• Fatigue often occurs because the compression and stretch
of the rod happen most of the time during the process.
• Eventually, this causes to wear of the rod till it gets
breaks.
• Lack of oil and the presence of dirt in the engine can
exacerbate this problem.
• This happens when cheap parts or wrong parts are used.
183

71. 2. Hydrolock
• Hydrolock occurs when water enters the piston chamber
causing deformation of the connecting rod.
• This may occur when vehicles pass through a flooded road.
• A little drop of water in the cylinder can produce knocking
or tapping in the engine.
• That can be easily corrected. But, if there is too much water
in the cylinder, the spark is all over the place for a period of
time, causing the cylinder rod to tilt or break.
184

72. 3. Over Revving
• That occurs in new and high-performance engines.
• If the tachometer displays a red color, it indicates that the position of
the connecting rod is in danger.
• This is because of forces working on the con rod rise dramatically at
higher revolutions.
4. Pin Failure
• Sometimes the piston pin is also damaged and results in catastrophic
engine failure.
• This occurs when the connecting rod moves into the engine block or
when the crankshaft is bent.
• In some engines, It can cause heavy power loss.
• The engine stops immediately when the pin breaks due to this
problem.
• There is a possibility that the engine has survived, otherwise, a total
breakdown may occur.
185

73. Applications of Connecting Rods
• It is a part of a piston engine that connects the piston to the
crankshaft.
• The connecting rod converts the reciprocating motion of the piston to
the rotation of the crankshaft.
• In the modern era, all types of machines inevitably depend on
pistons, connecting rods, and crankshafts.
• These components are needed for the precise functioning of
the internal combustion engine.
186

74. Crank Shaft
• The crankshaft is a moving
part of the internal combustion
engine (ICE).
• It’s main function is to
transform the linear motion of
the piston into rotational
motion.
• The pistons are connected to
the crankshaft through the
connecting rods.
• The crankshaft is mounted
within the engine block.
• The pistons, connecting rods
and crankshaft together form
the crank mechanism.
1.Pistons
2.Connecting rods
3.Flywheel
4.Crankshaft
187

75. Crankshaft
The secondary function of the crankshaft is to transmit power to other
engine systems:
• valve timing
• oil pump
• cooling (water) pump
• air conditioning compressor
• alternator, etc.
188

76. Crankshaft
• The crankshaft is fitted into the engine block through it’s main
journals.
• The connecting rods are fixed on the conrod journals of the
crankshaft.
• On opposite sides of the conrod journals the crankshaft has
counterweights which compensates outer moments, minimises
internal moments and thus reduces vibration amplitudes and bearing
stresses.
• At one end of the crankshaft the flywheel is connected and on the
other end the valve timing gearing.
189

77. Crankshaft
• The number of main journals
and conrod journals depends
on the number of cylinders and
the type of the engine (V-type,
straight, etc.).
• On both main journal and
conrod journals, the crankshaft
has lubrication orifices (oil
bore) through which oil flows
when the engine is running.
1.Control side or drive end
2.Counterweights
3.Main bearing journal
4.Conrod journal
5.Flywheel side/force transfer
6.Oil bore
190

78. 191

79. • Two types of crankshaft are produced, cast and forged. The
counterweights can be also forged directly onto the crankshaft or
bolted-on (fixed with threaded bolts).
• All the pistons of the internal combustion engine are transmitting
their forces to the crankshaft.
• From the mechanical point of view, the crankshaft has to withstand
high torsional forces, bending forces, pressures and vibrations.
Crankshaft
192

80. 193

81. Crankshafts for Multi-cylinder Engines
(Firing Order)
• To achieve better balancing of the dynamic (primary and secondary)
forces and their couples, the multi-cylinder engines have even number
of cylinders, i.e. 4 cylinder, 6 cylinder, 8 cylinder engines.
194

82. 195

83. 196

84. Valves
•Engine valves are mechanical components used in
internal combustion engines to allow or restrict the
flow of fluid or gas to and from the combustion
chambers or cylinders during engine operation.
197

85. Valves
• Engine valves are common to many types of combustion
engines, whether they run off a fuel such as gasoline, diesel,
kerosene, natural gas (LNG), or propane (LP).
• Engine types vary by the number of cylinders which are the
combustion chambers that generate power from the ignition
of fuel.
• They also vary by the type of operation (2-cycle or 4-cycle),
and by the design placement of the valves within the engine
[overhead valve (OHV), overhead cam (OHC), or valve in
block (VIB)].
198

86. Valve Assembly
199

87. Valve Mechanism
200

88. Engine Valve Nomenclature
• Most engine valves are designed as
poppet style valves because of their
up and down popping motion and
feature a conical profile valve head
that fits against a machined valve
seat to seal off the passage of fluids
or gases.
• They are also called mushroom
valves because of the distinctive
shape of the valve head.
201

89. Valves - Engine Operation
• The two primary elements are the valve stem and the valve head.
• The head contains a fillet that leads into a seat face that is machined at a
specified angle to match the machining of the valve seat to which it will match.
• The seating of the valve face to the valve seat is what provides the seal for the
valve against combustion pressure.
• The valve stem connects the valve to the mechanical elements in the engine that
operate the valve by creating a force to move the stem against the seating
pressure provided by a valve spring.
• The keeper groove is used to hold the spring in position, and the tip of the valve
stem is repeatedly contacted by a rocker arm, tappet, or lifter that actuates the
valve.
202

90. Valves - Engine Operation
• Four stroke or four-cycle internal combustion engines make use of
two primary types of valves – the intake valve and the exhaust valve.
• Intake valves are opened to allow the flow of an air/fuel mixture into
the engine’s cylinders prior to compression and ignition, while
exhaust valves open to permit the expulsion of exhaust gases from
the combustion process after ignition has occurred.
203

91. Valves - Engine Operation
• In normal operation, a crankshaft in the engine to which the pistons
are attached is tied to a camshaft as part of a valve train arrangement
for the engine.
• The movement of the crankshaft transfers motion to the camshaft
through a timing chain, timing belt, or other geared mechanism.
204

92. Engine Valve Motion
• The motion of the engine valves is driven by the camshaft of the
engine, which contains a series of lobes or cams that serve to create
linear motion of the valve from the rotation of the camshaft.
• The number of cam lobes on the camshaft is equal to the number of
valves in the engine.
205

93. Engine Valve Motion
• Maintaining the proper valve clearance between the valve stem and
the rocker arm or cam is extremely important for the proper
operation of the valves.
• If the valve clearance is too large, then the valves will open later than
optimally and will close sooner, which can reduce engine
performance and increase engine noise.
• If the valve clearance is too small, valves will not close fully, which
can result in a loss of compression.
• Hydraulic valve lifters are self-compensating and can eliminate the
need for valve clearance adjustments. 206

94. Engine Valve Materials
• Intake valves, because of their lower operating temperatures, are
typically made of materials such as chrome, nickel, or tungsten steel.
• The higher temperature exhaust valves may use more heat resistant
metals such as nichrome, silicon-chromium, or cobalt-chromium
alloys.
• Valve faces that are exposed to higher temperatures are sometimes
made more durable by the welding of Stellite, which is an alloy of
cobalt and chromium, to the valve face.
207

95. Engine Valve Materials
• Other types of material used for the fabrication of engine valves
include stainless steel, titanium, and tribaloy alloys.
• In addition, coatings and surface finishes can be applied to improve
the mechanical properties and wear characteristics of the engine
valves.
• Examples of this include chromium plating, phosphate plating,
nitride coating, and swirl finishing.
208

96. Types of Engine Valves
The primary types of engine valves include:
1. Monometallic engine valves
2. Bimetallic engine valves
3. Hollow engine valves
209

97. Monometallic engine valves
• Monometallic engine valves, as their name implies, are fabricated
from a single material that forms both the valve stem and valve head.
• These types of engine valves provide both high heat resistance and
exhibit good anti-friction capabilities.
210

98. Bimetallic engine valves
• Bimetallic engine valves, also known as bimetal engine valves, are
made by joining two different materials together using a friction
welding process to create a valve that has austenitic steel on the
valve head and martensitic steel for the valve stem.
• The properties of each of these steels serve an optimal purpose,
wherein the austenitic steel on the valve head provides high-
temperature resistance and corrosion resistance, and the martensitic
steel for the valve stem offers high tensile strength and abrasive wear
resistance.
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99. Hollow engine valves
• Hollow engine valves are a special bimetallic valve that contains a hollow
cavity that is filled with sodium.
• The sodium liquifies as the valve temperature rises and is circulated by the
motion of the valve, which helps dissipate heat from the hotter valve head.
• The hollow design facilitates greater heat transfer through the stem than
with solid valves because the martensitic stem material is a better
conductor of heat than the austenitic head material.
• Hollow valves are especially suited for use in modern engines that are
delivering more power out of smaller, denser engine designs that have
higher exhaust gas temperatures which solid valves are not capable of
handling.
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100. Hollow engine valves
These higher exhaust temperatures are the result of several conditions,
including:
• A desire for a lean-burn combustion process that reduces greenhouse
gas emissions
• Engine designs with higher compression ratios and higher
combustion pressures which offer greater efficiency
• Integrated manifold designs that support turbochargers for more
engine performance from smaller engines
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101. Engine Valve Specifications
• Stem diameter – the diameter of the engine valve stem
• Stem length – the distance from the stem tip to the valve head
• Seat angle – the angle cut of the valve head’s seat, measured in angular
degrees, typical values being in the range of 20o – 60o
• Valve materials – describes the material or materials used for the valve
fabrication
• Coatings – identifies any coatings or surface treatments applied to the
base material of the valve, such as chrome plating, nitride, PVD, or
ceramics, for example
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102. Lubrication system: Types, Oil pumps,
Filters
• To supply lubrication oil between the moving parts is
simply termed as lubrication.
• Improper lubrication of the engine will cause serious trouble
such as scored cylinders, dirty spark plugs, worn or burned-
out bearings, misfiring cylinders, stuck piston rings, engine
deposits and sludge and excessive fuel consumption.
215

103. Objects of Lubrication
The primary objects of lubrication are as follows:
1. Reduce friction between the moving parts.
2. Reduce wear of the moving parts.
3. Act as a cooling medium for removing heat.
4. Keep the engine parts clean, especially piston rings and ring grooves, oilways
and filters.
5. To absorb shocks between bearings and other engine parts, therefore, reducing
engine noises and increasing engine life.
6. To form a good seal between piston rings and cylinder walls.
7. Prevent deposition of carbon, soot and lacquer.
8. Absorb and carry away harmful substances resulting from incomplete
combustion.
9. Prevent metallic components from corrosive attack by the acid formed during
the combustion process.
10. To resist oxidation which causes sludge and lacquers. 216

104. 217

105. Types of Lubrication System
Following are the 6 main types of lubrication system:
1. Petrol system
2. Splash system
3. Pressure system
4. Semi-pressure system
5. Dry sump system
6. Wet sump system
218

106. Petrol System
• In these types of the lubrication system, it is commonly used in
the two-stroke petrol engines such as scooters and motorcycles. It is
the simplest form of the lubricating system. For lubrication purpose,
it does not have any separate part like an oil pump.
• But the lubricating oil is added to the petrol itself during filling in the
petrol tank of the vehicle in a specified ratio. When fuel enters the
crank chamber during engine operation, oil particles go down
into the bearing surfaces and lubricate them. The piston rings,
cylinder walls, piston pins, etc. are easily lubricated in the same way.
• If the engine is allowed to remain unused for a considerable time, the
lubricating oil separates off from petrol and starts to clogging of
passages in the carburettor, occurring in engine start problems. Thus
is the main disadvantages of this system.
219

107. Splash System
• In these types of lubrication system, the lubricating oil accumulates
in an oil trough or sump.
• A scoop or dipper is made in the lowest part of the connecting rod.
• When the engine runs, the dipper dips in the oil once in every
revolution of the crankshaft and cause the oil to splash on the
cylinder walls.
• This action affects engine walls, piston rings, crankshaft bearings,
and large end bearings.
• Splash system mostly works in connection with the pressure system
in an engine, some parts being lubricated by splash system and the
other by a pressure system. 220

108. 221

109. Pressure System
• In these types of lubrication
system, engine parts are
lubricated under pressure feed.
• The lubricating oil is stored in a
separate tank or the sump, from
which an oil pump receives the
oil through a strainer and
transfers it through a filter to the
central oil gallery at a pressure of
2-4 kg/cm2.
222

110. Semi-pressure System
• It is the combination of a
splash system and pressure
system of the lubrication
system.
• Some parts are lubricated by
splash system and some parts
by a pressure system
223

111. Dry Sump System
• The system in which lubricating of
oil collects in the oil sump is
known as a wet sump system as a
pressure system.
• The system in which the
lubricating oil is not located in the
oil sump is known as the dry
pump system.
• In this system, the vanes sweep
the oil from the inlet to the outlet
side.
224

112. Wet Sump System
• In this system, oil is transported to
various engine parts with a sump
strainer.
• In this wet sump system, oil
pressure is of about 4 to 5 kg/cm2.
After lubrication, the oil is carried
back to the oil sump.
225