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HET2 > 201j - Cylinder Head Fundamentals > Flashcards

201j - Cylinder Head Fundamentals Flashcards

1
Q

What method of construction is used to manufacture cylinder heads?

A

Casting

cast iron allow or aluminum

201j pg.4

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2
Q

Four-valve cylinder heads off what advantages over two-valve cylinder heads?

A
  • Volumetric efficiency
  • Turbulence

201j pg.5

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3
Q

On a two stroke engine, how many exhaust valves would there be with a two-valve cylinder head design?

A

Two exhaust valves

201j pg.5

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4
Q

What is a benefit of having more smaller valves instead of less larger valves?

A

Having more smaller valves offers greater combined valve head area and less valve inertia.

201j pg.5

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5
Q

What are injector tubes/cups usually made of? (3)

A
  • Copper
  • Stainless steel
  • Brass

201j pg.6

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6
Q

There must be a seal between the injector tube and the cylinder head to prevent: (2)

A
  • Coolant from leaking past tube into combustion chamber
  • Combustion gasses from leaking past tube into cooling system

201j pg.6

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7
Q

What component directs coolant flow to critical areas of the cylinder head?

A

Coolant directional nozzles

201j pg.8

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8
Q

What do coolant directional nozzles do?

A

Direct coolant flow to critical areas of the cylinder head such as exhaust valve seats.

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9
Q

Valves perform what two basic functions?

A
  • Open and close the cylinder to allow airflow during intake and exhaust events
  • Seal the cylinder during compression and power events

201j pg.9

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10
Q

What is the role of the valve lock groove?

A

Machined into the stem of the valve and mates with a lug on the valve locks. Valve locks and retainer keep the valve and spring together.

201j pg.9

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11
Q

What is the role of the valve fillet?

A

The smooth radius area between stem and face that provides strength and stress relief. The radius also enhances airflow past the valve.

201j pg.9

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12
Q

What is the role of the valve face?

A

Smooth machined surface that mates with the valve seat in the cylinder head to seal in combustion gasses and transfer heat.

201j pg.9

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13
Q

What is the role of the valve margin?

A

Material between the valve face and valve head. Supports the face and provides material for heat absorption.

201j pg.9

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14
Q

What are the different parts of a valve? (7)

A

Tip
Valve lock groove
Stem
Fillet
Valve face
Margin
Valve head

201j pg.10

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15
Q

Why is the exhaust valve typically made of better quality material than the intake valve?

A

Operates at higher temperatures and with corrosive gases.

201j pg.10

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16
Q

The lower end of certain valve stems are machined to a slightly smaller diameter. Why is this?

A

The machined step acts as a carbon scraper when it moves in and out of the valve guide. This helps keep the lower part of the valve guide clean and reduces carbon buildup.

201j pg.11

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17
Q

What percentage of cooling occurs through a solid valve stem between the valve face and valve seat?

A

75%

201j pg. 11

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18
Q

What percentage of cooling occurs in a solid valve stem between the valve stem and valve guide?

A

25%

201j pg. 11

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19
Q

A sodium cooled exhaust valve transfers approximately what percentage of its heat from the valve stem to valve guide?

A

50%

201j pg.12

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20
Q

Overall, sodium filled exhaust valves operate what percentage cooler than solid valve stems?

A

15%

201j pg.12

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21
Q

Valve face to seat contact is necessary to: (2)

A
  • Create an effective combustion chamber seal
  • Allow proper valve cooling

201j pg.12

22
Q

What are the two types of valve seats?

A
  • Integral
  • Removable / Replaceable

201j pg. 12

23
Q

What is Stellite?

A

Material that replaceable valve seat inserts are made of. A metal allow.

201j pg.13

24
Q

What material are replaceable valve seats made from?

A

Stellite
Hardened cast iron or metal allow

201j pg.13

25
Q

What are two types of valve guides?

A
  • Integral
  • Removable

201j pg.14

26
Q

What are the main roles of the valve spring?

A
  • Keeps the valve face in contact with the seat to seal the combustion chamber
  • Control valve oscillations
  • Keep the cam follower in cotact with the cam lobe as engine rpm increases

201j pg.14

27
Q

What are three types of valve springs?

A
  • Single
  • Double
  • Progressive

201j pg.14

28
Q

Single springs often use a flat inner spring. What is this spring for?

A

To counteract valve spring vibrations at higher rpm

29
Q

What is a benefit of double valve springs?

A

Increased valve spring tension in one assembly compared to a single valve spring.

201j pg.14

30
Q

What is valve float?

A

At higher rpm’s when the valve is not able to fully close before being opened again. Often caused by insufficient spring tension.

31
Q

How are progressive valve springs orientated when installed?

A

With the tightly-coiled side down

32
Q

What is the valve spring seat used for? (2)

A
  • Locate the valve spring and keep it centred over the guide
  • Prevent erosion of the cylinder head

201j pg.15

33
Q

What is used to prevent valve springs from eroding the cylinder head?

A

Spring seat

201j pg.15

34
Q

What is the role of the valve spring retainer?

A

Keeps the valve and spring as a unit with use of the valve locks. Also centres the spring over the valve.

201j pg.16

35
Q

What benefit does a positive valve rotator provide?

A
  • Provides a changing wear surface for even valve and seat wear
  • Creates a wiping action to help keep the valve face and seat clean of carbon

201j pg.16

36
Q

What are the two basic types of valve seals?

A
  • Positive
  • Non-positive

201j pg.19

37
Q

What materials are rocker arms usually manufactured from?

A
  • Forged steel
  • Allow cast iron

201j pg.21

38
Q

What range do typical rocker arm ratios fall between?

A

1.5:1 and 1:1

201j pg.22

39
Q

If a rocker arm had a ratio of 1.43:1 and the camshaft had a lobe lift of 0.256”, what would the valve opening measurement be?

A

1.43 * 0.256 = 0.366” lobe lift

201j pg.23

40
Q

What allows one rocker arm to open two valves simultaneously on a 4-valve cylinder head?

A

Valve bridges (Crossheads)

201j pg.25

41
Q

Pushrods form the link between ______ and _______ on engines with in-block mounted camshaft.

A

Cam follower & rocker arm

201j pg.25

42
Q

How are exhaust and fuel injector pushrods designed to compensate for the greater forces they see during engine operation?

A

Are made stronger and heavier

201j pg.25

43
Q

Some pushrods are constructed from solid metal, but most are made from high quality _______ to reduce weight.

A

Seamless alloy steel tubing

201j pg.26

44
Q

What is the purpose of the valve cover?

A
  • Keep dirt and moisture from entering the engine
  • Contain the oil that lubricates the valve mechanism

201j pg.27

45
Q

What are the two basic types of head gaskets?

A
  • Steel
  • Composition

201j pg.28

46
Q

What are the benefits and drawbacks of steel head gaskets?

A

Maximum resistance to the forces of heat and combustion

Lack conformability

201j pg.28

47
Q

What are the two basic design types of head gaskets?

A
  • One-piece
  • Multi-piece

201j pg.29

48
Q

What two methods are used to retain cylinder heads?

A
  • Cap screws
  • Studs

201j pg.31

49
Q

Valve carbon scrapers are used to prevent carbon buildup on what?

A

The lower part of the valve guide

201j pg. 11

50
Q

The grinding of what two sealing surfaces would result in an increased spring height and stem height?

A
  • Valve face
  • Valve seat

HET2 (29 decks)

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