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crankshaft bearings and related components > camshaft > Flashcards

camshaft Flashcards

1
Q

function of the cam shaft

A

.Controls the opening and closing of the valves
.Changes rotary motion into reciprocating motion
.Actuates the injector operating mechanism on engines with fuel injectors

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2
Q

Depending on engine design camshaft gear train may also drive

A

.Fuel injector pump
.Fuel transfer pump
.Tachometer
.oil pump

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3
Q

Camshaft components

A 
Nose
Keyway 
Journals 
Injector lobe 
Valve lobes
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4
Q

Camshaft nose

A

mounting surface for camshaft drive gear or sprocket

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5
Q

camshaft Keyway

A

maintains alignment between camshaft and drive gears

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6
Q

Journals

A

Load bearing surface that supports the camshaft in the cylinder block or head

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7
Q

camshaft lobes

A

convert rotary motion of the camshaft into reciprocating motion of the cam follower

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8
Q

Auxiliary drive gear on a camshaft

A

machined onto the shaft used to drive oil pump or tachometer

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9
Q

cam lobe design controls

A

valve timing as well as rate at which valves open and close

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10
Q

three factors that will determine camshaft lobe design

A

hoarse power
speed of operation
naturally aspirated or turbocharged

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11
Q

camshaft lobe terminology

A

Nose
Lift
Ramp
Base circle

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12
Q

Nose of a cam lobe

A

maximum point of lift

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13
Q

Camshaft lobe ramp

A

is the slope the follower will ride up and down on

There is an opening and closing ramp on all camshaft lobes

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14
Q

Cam lobe Base circle

A

is the base diameter of the camshaft lobe

at this point there is no valve opening

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15
Q

Cam lobe lift

A

Is the distance the cam follower moves as it travels to the top of the cam lobe
Lift can be determined by subtracting base circle diameter from lobe height

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16
Q

Duration

A

the number of degrees between the point where the valve opens and the valve closes
actual amount of degrees is measured in crankshaft rotation

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17
Q

three types of camshaft construction

A

Casting
Machined or forged from alloy steel
Assembled from components

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18
Q

Cast camshafts

A

used in low hoarse power or light and medium duty diesel engines
Can be chipped or broken easily if not handled with care

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19
Q

Steel camshafts

A

used in engines where extreme loads are placed on the camshaft
journals and lobes are hardened to improve durability

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20
Q

Molybdenum disulphide and manganese phosphate are used on cast camshafts for

A

pressure resistant and anti wear properties

retains oil prevents scuffing and promotes quick break in of the lobes when engine is first started

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21
Q

Modular camshafts

A

used in large displacement engines

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22
Q

camshaft locations

A

In-block and overhead

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23
Q

Advantages of an overhead camshaft

A

.Fewer moving parts
.Less friction
.More accurate vale timing

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24
Q

camshaft bearings

A

used to support the camshaft and control end play

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25
Q

most common method of controlling camshaft end play

A

thrust washer or plate

usually located behind the camshaft drive gear and bolts to the cylinder block

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26
Q

purpose of the cam follower

A

provides a link between the cam lobe and the valve operating mechanism
converts rotary motion into reciprocating

27
Q

Types of cam followers

A

Solid
roller
Hydraulic

28
Q

two types of solid followers

A

straight body

mushroom

29
Q

Advantage of solid type mushroom lifter

A

have a greater surface area therefore will withstand higher contact pressure

30
Q

three factors of solid followers that provide a changing wear surface

A

Slight taper from one edge to the other aprox .001”
bottom face will not be flat but convex (crowned)
Lifter centerline is offset from the cam lobe center line

31
Q

Advantage of a slight crown on a solid follower

A

allows a larger contact point and prevents edge loading of the cam lobes

32
Q

Why must valve operating mechanism have clearance or lash when used with solid type followers

A

to allow for heat expansion

33
Q

Roller type lifters

A

can be solid or hydraulic in design bottom of the lifter has a wheel or roller retained by a pin and supported by a bushing

34
Q

to prevent roller type lifter from turning in the lifter bore

A

positioning mechanism will be used

35
Q

Three advantages to a roller type lifter

A

reduce frictional loss
can handle much higher operating loads
allow for quicker open and close rates of valves

36
Q

Advantage of a hinged type roller

A

eliminates the need for follower bores as well as side thrust created by conventional roller followers
also can handle very high operating loads

37
Q

Hinged roller design normally used on

A

engines with mechanically actuated fuel injectors

38
Q

two advantages of a hydraulic lifter

A

compensates for normal heat expansion and normal wear eliminating the need for valve clearance (lash) and periodic adjustments
reduced noise because components are in continual contact

39
Q

hydraulic lifters are normally used in small displacement diesel engines because

A

cost and reliability

40
Q

Internal leakage of a hydraulic lifter under pressure is referred to as

A

the leakage rate

41
Q

OHV and OHC

A

overhead valve engines

overhead camshaft

42
Q

camshaft drive mechanism

A

provide a positive method to drive the camshaft and any camshaft driven components
establish a relationship between crankshaft and camshaft for timing

43
Q

Two methods for driving a camshaft

A

gears or chains

44
Q

idler gears in an engine are used when

A

physical distance between the camshaft and the crankshaft is to great

45
Q

two types of timing chains

A

silent type for light and medium duty engines

roller type for heavy duty engines

46
Q

one of the most critical steps in reassembling an engine is

A

camshaft timing as it determines firing order and correct valve timing

47
Q

Incorrect camshaft timing will result in

A

altered valve opening and closing points
poor engine performance
damage to the engine components
altered fuel injection timing on engine camshaft actuated injectors

48
Q

another method of camshaft timing

A

offset keys

can be installed in either direction to retard or advance cam timing

49
Q

A round eccentric on a camshaft would be used for what purpose

A

to drive an engine mounted fuel transfer pump

50
Q

two locations to measure gear backlash on the engine

A

between the crankshaft and idler and the idler and the camshaft

51
Q

worn teeth on a gear will result in

A

retarded timing

52
Q

chain drive slack should not exceed more than

A

1/2 “

53
Q

mushroom type lifters must be removed after the camshaft because

A

the large surface of the lifter will not allow them to be removed from the top side of the cylinder block

54
Q

two indications of a bent camshaft

A

binding or a tight spot when rotating the camshaft in the cylinder block
uneven cam bearing wear

55
Q

method used for measuring fuel injector lobes on a camshaft

A

flat block and feeler gauge

56
Q

when checking solid type lifter for reuse

A

check for scuffing and scoring on the lifter sides
scuffing, scoring and pitting on the face
must have convex shape

57
Q

extreme cupping of a solid type lifter

A

lack of lubrication
long service life
poor maintenance

58
Q

excessive camshaft end play will cause

A

drive gear noise and excessive wear to components

59
Q

when removing camshaft bushings from their bores

A

use a special driver or puller

60
Q

after camshaft bearings are installed you should check for

A

proper alignment of the oil holes using a alignment tool

61
Q

if the camshaft gear must be heated for installation the thrust washer must not be

A

lubricated

62
Q

lobes require special lubrication when being installed because

A

scuffing action between lifters and cam lobe

manufacture my require special EP lubricant (extreme pressure)

63
Q

three factors that may cause camshaft end play

A

thrust plate installed backward
thrust plate misalignment
foreign material between the thrust plate and camshaft or gear

crankshaft bearings and related components (3 decks)

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