The document discusses the key components that make up the bottom end of an engine, including the engine block, crankshaft, connecting rods, pistons, rings, and bearings. It describes the materials, functions, and terminology associated with each part. The crankshaft converts the reciprocating motion of the pistons into rotational motion to power the vehicle. Pistons harness the energy of combustion and transfer force to the crankshaft via connecting rods. Precise clearances and alignments are needed for proper engine operation and longevity.

1. 1
ENGINE CONSTRUCTION

2. 2
Engine Block Assembly
 Very sophisticated
casting.
 Made of cast iron or
aluminum with cast
iron cylinder liners.
 A great deal of
machining involved in
the process of
manufacturing.
 Becomes the frame of
the engine.

3. 3
Engine Bottom End

4. 4
Bottom End Parts
 Block
 Crankshaft
 Connecting Rod
 Pistons, Rings, & Wrist Pin
 Bearings (Main and Connecting rod)
 Caps (main and Connecting Rod)
 Fly Wheel and nuts and bolts

5. 5
Cylinder Block
Common cylinder
configurations:
Vee, inline, opposed
And slant.
Number from
farthest front
backwards

6. 6
Crankshaft
 Converts
reciprocating
motion into rotary
motion.
 Made of either
nodular iron,
forged steel, or
billet steel.

7. 7
Crankshaft Terminology
 Crankpins or throws
 Main bearing journals
 Rod bearing journals
 Thrust bearing
 Main caps
 Oil passages
 Flywheel flange
 Vibration damper
end
 Keyway
 Rear main seal
 Front crankshaft seal
 Counter weights
 Firing order

8. 8
Crankshaft Bearings
 Known as friction or
precision insert
bearings.
 Uses a steel backing
with soft metal on
crankshaft side.
(lead,tin, copper,
silver, cadmium)
 Oil clearance between
crankpin and bearing
very critical. (.001”)
 Oil Clearance
measured with
plastigauge.

9. 9
Crankshaft Service
 Grinding Cranks
 Undersize bearings

10. 10
Flywheel
 The flywheel (known as
the flex plate when used
with an automatic
transmission) carries the
engines inertia in between
power strokes.
 It is the power take off for
the engine. The clutch or
torque converter bolts to
it.
 Lastly it has the starter
motor’s ring gear.

11. 11
Vibration Damper
 The vibration damper
smoothes the
vibrations caused by
the power strokes.
 It has a pulley on it
the run auxiliary
systems.
 It may contain timing
marks or crankshaft
timing sensors.

12. 12
Balancer Shafts
 Used to counteract
the normal
vibrations inherent
to piston engines.
 Found on 4
cylinder and 6
cylinder engines
mostly.

13. 13
Covers & Pans
 Made of steel
metal, aluminum,
or plastic
materials.
 Usually use
gaskets or seals.

14. 14
Gaskets, Seals and Sealers
 Gaskets seal two
stationary surfaces.
 Seals do it when one
surface moves.
 Many types of
materials: rubber,
paper, aluminum,
steel, cork and more.
 Sealers adhere
gaskets to one of the
surfaces.

15. 15
Pistons
Pistons harness
the energy of
the power stroke
and transfers the
force toward
the crankshaft.

16. 16
Piston Terminology
 Head or crown
 Ring grooves
 Ring lands
 Oil return holes
 Skirt
 Pin hole
 Pin boss
 Pin offset

17. 17

18. 18
Piston Rings
 Rings seal the
compression in the
combustion chamber
and the motor oil in
the crankcase.
 Automotive engines
use 3 rings: 2
compression and 1
multi-piece oil ring.

19. 19
Piston Ring Wear
 Causes a loss of
compression.
 Causes excessive
oil consumption.
May cause blue
smoke out the tail
pipe.

20. 20
Types of Piston Rings
 Rings are usually
made of cast iron
 can be plated with
chrome or
molybdenum.
 Help seal the ring to
the cylinder wall.
 Shapes of the ring
vary to also help the
ring seal better.

21. 21
Piston Pin (Wrist Pin)
 Hollow polished steel
pin.
 Attached in a variety
of ways.
 Pinned to piston.
 Clamped to rod small
end.
 Snap ring free
floating.
 Press fit.

22. 22
Connecting Rods
 I-beam style rod use
to transfer the pistons
force to the
crankshaft.
 Small end contains
the piston pin and the
big end has a
removable cap to
install it to the Crank.
 Nuts and bolts are
usually of a very high
quality.

23. 23
Installation of Pistons
 Cylinder number
 Piston number
 Notch to the front
 Position ring gaps
 Remove rod cap check bearing inserts
 Cover bolts with fuel line if needed
 Crankshaft at TDC or BDC
 Install ring compressor
 Oil piston, cylinder wall, & crank journal
 Carefully tap in piston with hammer handle.
 Properly replace rod cap

24. 24
Rods MUST match caps

25. 25
Weird Science of Engines
 Free running and Non-free running
 Crankshaft rotation versus piston
travel
 Piston side thrust
 Piston pin offset
 Cylinder bore wear
 Crankshaft journal wear

26. 26
Free and Non-Free running
Engines
 Free running
engines can have
their piston at TDC
and their valves
wide open and the
valve won’t touch
the piston.
 Non-free running
engines will crash
the valves into the
piston if the piston
is at TDC and the
valves are wide
open. This will
wreck the engine.

27. 27
Piston Travel Verses
Crankshaft Rotation
 When the piston
move ½ way down
the bore the
crankshaft does
not turn a ½ a
turn. This will
always create
vibration.

28. 28
Piston Side Thrust
 There are two sides to
the piston.
 The thrust side and
the relief side.
 Wear occurs mainly
on the thrust sides.
 Skirt area is not even
needed on the relief
side.
 Piston pin offset
counteracts side
thrust.

29. 29
Cylinder Bore Wear
 Wears oval
shaped.
 Cylinder wall
tapers.
 Pocket forms near
the top.
 A ridge forms at
the top.

30. 30

31. 31
http://wn.co
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32. 32
http://wn.com/four_stroke_engine

33. 33
Cylinder Boring
 Cylinders can be
bored to restore
them however
they will be larger
requiring bigger
pistons.
 Usually bored to .
010”, .020”, .030”,
or .050”

34. 34
Crankshaft Wear
 Wears out of round
due to the power
strokes.
 Grinding can
restore the
journals, however
they are smaller
requiring under
sized bearings.