Chapter 11 - PowerPoint Presentation

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Chapter 11

Lower End Theory and ServiceSlide2

Engine Lower End

The lower end of an engine is the cylinder block assembly

Includes the block, crankshaft, bearings, pistons, connecting rods, oil pump, and camshaft on OHV designs

This assembly is called a short block

A short block plus the cylinder head(s) is called a long blockSlide3

Lower EndSlide4

Short Block Disassembly

Remove oil pan and water pump

Remove the harmonic balancer

On OHV engines remove the timing cover

Inspect the timing chain and remove

Remove the oil pick up and oil pump

Remove lifters and keep them in orderSlide5

Cylinder Block Disassembly

Check balance shaft clearances if necessary and remove

Rotate crankshaft so cylinder #1 is at BDC

Carefully remove all cylinder ring ridgesSlide6

Cylinder Block Disassembly

Check bearing cap positions and mark if necessarySlide7

Cylinder Block Disassembly (Cont.)

Position piston at BDC for removal

Remove connecting rod cap and cover rod bolts to prevent cylinder damage

Carefully push the piston and rod with wooden handle

Be sure connecting rod does not damage the cylinder wallSlide8
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Cylinder Block Disassembly (Cont.)

Remove the main bearing caps in the specified order

Some engines use a main bearing girdle or bedplate that houses the bearings

Carefully remove crank and store vertically

Remove the rear main oil seal and bearing insertsSlide10

Cylinder Block Disassembly (Cont.)

Remove the block core plugs and oil plugs to ensure thorough cleaning

Oil gallery plugsSlide11

Cylinder Block

Houses areas where combustion takes place

Can be cast iron, aluminum or magnesium

Cast iron is very strong but heavySlide12

Cylinder Block (Cont.)

Most aluminum blocks use cylinder liners

Usually cannot be machinedSlide13

Oil and coolant passages within the block allow for the flow of oil and coolant

Cylinder Block (Cont.)Slide14

Block Reconditioning

Inspect the block for cracks and damage

Clean all threaded bores with a thread chaser

Bolt holes should be slightly chamferedSlide15

Block Reconditioning (Cont.)

Aluminum blocks with damaged threads may require a threaded insert – called a HelicoilSlide16

Block Reconditioning (Cont.)

Deck flatness is important for proper cylinder head and intake manifold fitSlide17

Block Reconditioning (Cont.)

Inspect cylinder walls

Wall scoring or scuffing

Most wear is at top of cylinder

Measure taper and out-of-roundnessSlide18

Cylinder Bore Finish

Surface finish must act as an oil reservoir

Rings can be damaged by a rough surface

Too smooth will not hold enough oil

Desired finish is a crisscross patternSlide19

Cylinder Bore Finish (Cont.)

Deglaze if cylinder condition is within specifications

Honing removes a small amount of metal from the cylinder walls

Boring is performed when the cylinder walls are worn excessively

Oversized pistons and rings are used after boringSlide20

Knowledge Check

What may result if the cylinder bore finish is too smooth?Slide21

Lifter Bores

Inspect bores for cracks and excessive wear

Can be honed with a wheel cylinder hone

If the lifter bores exceed allowable wear, the block should be replacedSlide22

Crankshaft Saddle Alignment

Misalignment will cause the crankshaft to bend as it rotates

May be repaired by line boring

Badly warped blocks are replaced

Checked along the crankshaft saddle bore

Roundness should be checked as wellSlide23

Crankshaft Saddle AlignmentSlide24

After cleaning, the block should have new core and oil plugs installed

Coat the plug or bore lightly with a non-hardening sealer

Installing Core PlugsSlide25

Camshafts

Have a cam lobe for each exhaust and intake valve

Lobe height is proportional to valve lift

May drive distributor and/or oil pump

May be iron, steel, or hollowSlide26

OHV Camshafts

Works with lifters, pushrods, and rocker arms to open the valvesSlide27

Camshaft in BlockSlide28

OHC Camshafts

May be single or dual overhead camshafts

Can open valves directly or through lifters, followers, or rocker armsSlide29

Camshafts (Cont.)

Driven at half of crankshaft speed

Cam gears are twice the size of crank gears

Each intake and exhaust valve opens and closes once per crankshaft rotation

Valve opening and closing based on the shape of the cam lobeSlide30

Camshaft Terminology

The shape of the cam lobe is called the cam profile

Duration is the time the valve is open

Overlap is the time both the exhaust and intake valves are open at the same timeSlide31

Lobe TerminologySlide32

Camshaft Drives

Belt Drive

Sprockets on the crankshaft and the camshaft are linked by a neoprene beltSlide33

Camshaft Drives

Chain Drive

Sprockets on the crankshaft and the camshaft are linked by a continuous chainSlide34

Camshaft Drives

Gear Drive

A gear on the crankshaft meshes directly with a gear on the camshaftSlide35

Camshaft Drives (Cont.)

Tensioners may be spring loaded and/or hydraulically operated

Maintains correct belt or chain tension

Have a drive side and a slack side

The tensioner is on the slack sideSlide36

Variable Valve Timing (VVT)

VVT used on OHC and OHV engine designs

VVT systems use special camshafts and phasersSlide37

Knowledge Check

What are the three types of camshaft drives?Slide38

Lifter Types - Hydraulic Lifter

Hydraulic Lifters

Uses oil to absorb the shock from the valve train movementSlide39

Lifter Types - Solid Lifter

Solid Lifters

Require a clearance between parts of the valve trainSlide40

Lifter Types - Roller Lifter

Roller Lifters

Uses a roller to minimize frictionSlide41

Camshaft Bearings

OHV engines are one piece bearings pressed into the camshaft bore

OHC can be supported by split bearingsSlide42

Balance Shafts

Balance or silence shafts are used to reduce engine vibration

Counterweights mirror the throws of the crankshaft

Rotate opposite crankshaft rotation

Inspected and serviced as part of engine reconditioningSlide43

Balance Shaft (Cont.)Slide44

Crankshafts

Made of iron or steel

Crankshaft main and rod journals are machined to very close tolerances

This allows an oil film between the journal and the bearingSlide45
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Crankshaft Torsional Dampers

Crankshaft twists and bends under combustion forces causing harmonic vibrations

This vibration can damage the crankshaft, the engine, and/or accessories driven by the crankshaft

Two common types of torsional dampers usedSlide47

Harmonic Balancer

Also called a vibration dampener

Composed of an inner hub and outer inertia ring connected via a rubber sleeve

As the crank twists the hub applies force to the ring

The condition of the sleeve is criticalSlide48

Harmonic BalancerSlide49

Fluid Damper

Commonly installed by the aftermarket

Fluid filled dampers have a hub surrounded by the inertia ring

The ring is filled with a high viscosity fluid

The outer ring moves against the hub as it absorbs vibrations

This movement results in heatSlide50

Flywheel

Helps the engine run smoother

Applies a constantly moving force to the crankshaft

Flywheel inertia helps keep the crank moving from one firing event to the next

On automatic transmissions, the flex-plate and torque converter act as a flywheelSlide51

Check vibration damper and flywheel mounting surfaces for fretting or erosion

Look for indications of damage from previous engine failures

Check journals for signs of overheating

Check sealing surfaces for scoring or wear

Check for surface cracks

Crankshaft InspectionSlide52

Journal InspectionSlide53

Crankshaft Reconditioning

If severely damaged, the crank should be replaced

Slight journal taper, light grooves, burnt marks, or small nicks could allow reuse

Minor journal damage may be corrected by polishing with a very fine sand paperSlide54

Crankshaft Straightness

Checked by supporting the crank in V-blocks at the end main bearing journals

Position a dial indicator to measure at the center main bearing journal

Turn the crank one full rotationSlide55

Crankshaft Bearings

Called insert bearings

A split bearing with a flanged side is a thrust bearing

Many engines use bedplates instead of individual bearing caps

Tightening procedures must be followedSlide56
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Bearing Materials

Aluminum alloy

The most commonly used design

Aluminum

Copper and lead alloys

Steel backings coated with babbitt

Layered combination of metalsSlide58

Bearing Spread and CrushSlide59

Locating lugs fit into slots in the bearing bore

Oil grooves provide an adequate oil supply

Oil holes allow control of oil flow to other parts of the engine

Bearing Locating DevicesSlide60

Knowledge Check

What is the purpose of the flanged main bearing?Slide61

Installing Main

Bearings and Crankshaft

If there is little or no wear on the journals, standard sized bearings can be used

If the journals are excessively worn, undersized bearings must be used

Undersized bearings are thicker since the crank journals are smallerSlide62
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Installing Main

Bearings and Crankshaft (Cont.)

Plastigage is used to determine main and rod bearing clearances

Insert between the bearing and journal

Torque and then loosen the bearing capSlide64
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Crankshaft End Play

Can be measured with feeler gauges or dial indicator

End play can be adjusted by replacing the main thrust bearing or washers

The crankshaft rear mail seal is usually installed during the final installation of the crankshaftSlide66
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Connecting Rods

Transmits the pressure on the piston to the crankshaft

Made of steel, iron, aluminum, and titanium

The small end contains the piston pin

The big end attaches to the crankshaft and is in two pieces

May supply oil to cylinder wallSlide68
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Pistons and Piston Rings

The piston forms the lower portion of the combustion chamber

Most are made of aluminum alloys

Piston heads can be flat, concave, convex, crowned, raised, and relieved for valvesSlide70

Pistons and Piston Rings

Below the head are the ring grooves and lands

Below the rings is the piston pin or wrist pinSlide71

Pistons and Piston Rings (Cont.)

The area below the pin is the piston skirt

Two types of skirts are used - the full skirt and the slipper skirt

Full skirts are used in truck and commercial enginesSlide72

Pistons and Piston Rings (Cont.)

The top of the piston has a direction mark

Mark or arrow points to the front of the engineSlide73

Check for damage and cracks, or scuffing on sides of the piston

Use a piston ring expander to remove rings

Clean carbon from piston top and ring grooves

Measure ring side clearance – between the ring and the top of the ring groove

Piston diameter should be measured

Piston InspectionSlide74

Piston Pins

Hollow steel tubes

Lubricated by oil fed through connecting rods

Stationary pins are pressed into the piston

Semi-floating pins are pressed into rod

Full-floating pins are retained by caps, plugs, snap rings, or clipsSlide75
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Piston Pins (Cont.)

Inspect pin area on piston for wobble

Inspect pin for wear and pin bore in piston

Any movement up and down indicates either pin or piston needs replaced

Connecting rod may have a pin bushingSlide77

Seal the combustion chamber at the pistonRemove oil from the cylinder walls to prevent oil from entering the combustion chamber

Carry heat from the pistons to the cylinder walls to help cool the piston

Piston RingsSlide78

Compression RingsForm the seal between the piston and the cylinder wall

Most piston designs use two compression rings

Oil Control Rings

Control oil used to cool piston and lubricate cylinder walls

Piston Ring TypesSlide79

Piston RingsSlide80

Installing Rings

Check ring end gap

Apply a light coat of oil to the rings

Install the oil control ring first, staggering the ends of the three parts

Install the second then first compression rings

Ensure the correct side is facing up

Place ring gaps per specificationsSlide81
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Knowledge Check

What is the correct order for installing piston rings?Slide84

Installing Pistons and Rods

Ensure caps and rods are a match

Insert bearings into rods and caps

Oil the cylinder walls

Coat the crankshaft journals with oil

After each piston in installed, rotate the crankshaft to check its movementSlide85

Checking Crankshaft RotationSlide86

Inspection of Camshaft

and Related Parts

Check each lobe for scoring, scuffing, fracturing, pitting, and signs of abnormal wear

Premature lobe wear is usually due to inadequate lubrication

Measure cam bearing journal diameter

Check for straightness with a dial indicatorSlide87

Timing Components

Measure timing gear backlash

Excessive backlash causes gear noise

Insufficient backlash causes gear bindingSlide88

Lifters

Inspect cam side for wear

Improper lubrication will cause excessive wear

Disassemble and clean lifters

Perform a leakdown test

Never use old lifters on a new cam or an old cam with new liftersSlide89

Checking Lifter WearSlide90

Installation – Camshaft Bearings

Cam-in block bearings may be easier to install if crankshaft is not installed

Bearings are press fit into block using a driver

Some cam journals have different diameters

Smallest at the rear of the block and each journal progressively largerSlide91

Camshaft Bearing InstallationSlide92

Installation - Camshaft

Thoroughly coat with assembly lube

Lubricate the lifters

Carefully install cam to avoid bearing damage

Install the thrust plate and cam gear

Once installed, turn the cam by handSlide93

Crank and Cam Timing

Timing must be set to specifications

Install the chain on the crank gear first

Never wind or pry a chain onto the gears

Check camshaft end play if requiredSlide94

Typical balance shaft timing mark arrangementSlide95

Balance Shafts

Inspect each bearing and journal

Check oil clearances with plastigage

Apply a light coat of oil to the bearings

Align the timing marks and set the shafts into positionSlide96

Oil Pumps

Positive Displacement Pumps

The amount of oil that leaves is the amount that entered

Output volume is proportional to pump speed

Internal engine passages restrict oil flow, causing oil pressure

Oil pressure affected by oil viscosity and temperatureSlide97

Knowledge Check

What may result from the balance shaft not being properly timed?Slide98

Rotor-type oil pump

Gear-type oil pump

Types of Oil Pumps