190201h

Question 1

On engines with UNIT fuel injectors the cam also actuates

Answer 1

the injector operating mechanism

Question 2

the cam is driven by the crank and changes motion from what to what?

Answer 2

rotary motion into reciprocating

Cam to followers

Question 3

Cam nose is a mounting surface for the drive gear or sprocket. What maintains alignment of the gear to cam

Answer 3

a keyway is machined into the nose to retain the key

Question 4

What are the load bearing surfaces of the cam

Answer 4

Journals. they support the cam in the block

Question 5

Lobes are eccentrics that convert the rotary motion of the cam to…

Answer 5

reciprocating motion of the cam follower

Question 6

depending on the engine, the cam gear train may also run the

Answer 6

fuel injection pump, fuel transfer pump, oil pump , tach

Question 7

what is a helical gear machined into a cam most likely to run?

Answer 7

oil pump or tach

Question 8

the nose on a cam lobe is…

Answer 8

the point of maximum lift

Question 9

the centerline is the

Answer 9

point between opening and closing ramps

Question 10

what part of the lobe does a lifter ride up and down on?

Answer 10

the opening and closing ramps. there is one on all lobes

Question 11

what is the base circle

Answer 11

the base diameter of the lobe and no valve is open on it

Question 12

what math formula on what parts gives you calculated lift?

Answer 12

subtract base circle from the lobe height

Question 13

What is the definition of “Duration”

Answer 13

the number of degrees between where the valve opens to the point where it closes

Question 14

What are the three ways camshafts are manufactured

Answer 14

Casting, machine or forged from alloyed steel and assembled from components

Question 15

Why are cast camshafts heat treated

Answer 15

To improve durability

Question 16

When new most camshafts have a black coating on the lobes. What is it?

Answer 16

Pressure resistant antiwear agents molybdenum disulfide or manganese phosphate

Question 17

Where would you use a steel camshaft

Answer 17

Where extreme loads are placed on the camshaft such as with unit fuel injectors

Question 18

Why would you use a modular camshaft

Answer 18

In some large displacement diesel engines or to permit ease of manufacturing and service

Question 19

What are the two general camshaft locations

Answer 19

In block or overhead

Question 20

Camshaft motion is transmitted how with the in block design

Answer 20

Through the cam follower and pushrod to the rocker arm

Question 21

What are the advantage of the overhead camshaft

Answer 21

Fewer moving parts, less friction, more accurate valve timing

Question 22

What type of bushings are generally used to support the camshaft and control and play

Answer 22

Friction type bearings

Question 23

How are bushings normally retained in the cylinder block

Answer 23

Bushings are retained by a press fit in the cylinder block cam bearing bores

Question 24

Many diesels with overhead camshaft use what type of bearings

Answer 24

Shell type bearings. Which permits the camshaft to be removed vertically from the cylinder head

Question 25

True or false. The camshaft is one of the last components to receive oil

Answer 25

True

Question 26

What are three different ways to limit end play of the camshaft

Answer 26

Taper of the camshaft lobes. Cam shaft driven by helical gears. A thrust plate or washer is the most common method of controlling and play on diesel engine camshafts

Question 27

What two ways are camshaft lobes lubricated by oil

Answer 27

Sprayed out of the camshaft bearing and splashed off the valve operating mechanism

Question 28

What's the purpose of a cam follower

Answer 28

Turn the rotary motion of the camshaft into reciprocating motion by following the profile of the cam lobe

Question 29

What are the three basic types of cam followers

Answer 29

Solid, roller and hydraulic

Question 30

What are two other names for cam followers

Answer 30

Lifters or tappets

Question 31

What are two types of flat faced solid lifters

Answer 31

Straight body and mushroom

Question 32

What is the advantage of a mushroom type solid lifter over a straight body lifter

Answer 32

Mushroom type have a greater surface area in contact with the cam lobe and will therefore withstand higher contact pressure

Question 33

What are three ways a solid lifter is kept from wearing quickly

Answer 33

The lifter has a concave, the lobe has a taper, the lifter centerline is also offset in relation to the cam lobe creating rotation

Question 34

A solid cam follower has no mechanism to compensate for heat expansion therefore what must be in place

Answer 34

There must be some clearance or valve lash to allow for expansion as temperature increases

Question 35

Roller lifters can either be a solid or hydraulic design. What are three characteristics

Answer 35

The cam lobe for a lifter is ground flat and has no taper. The roller is usually centered on the cam lobe for Full Contact. It cannot turn during operation and will have a positioning mechanism to prevent it from turning

Question 36

Roller type cam followers reduce what three things

Answer 36

They reduce friction, wear, and sides thrust on the lifter body

Question 37

What are three advantages of roller type cam followers

Answer 37

Reduced frictional loss, can handle much higher operating loads, allow a quicker rate of valve opening and closing then solid cam followers

Question 38

Overhead cams have what built into the rocker arm

Answer 38

A cam follower roller

Question 39

What are two things a hinged roller eliminates

Answer 39

The need for lifter bores in the cylinder block and side thrust created by conventional roller followers

Question 40

What engine design uses the hinged roller

Answer 40

Primarily used on engines with mechanically actuated fuel injectors. It opens both valves and injectors

Question 41

What are the two advantages of hydraulic lifters over solid lifters

Answer 41

Hydraulic operated lifters compensate for heat expansion therefore no valve lash is necessary and hydraulic lifters operate with no valve clearance and all valvetrain components are in continual contact during engine operation resulting in less valvetrain noise

Question 42

What are two ways timing gears are installed on the camshaft and two ways that they are indexed

Answer 42

They are bolted or pressed on and indexed by a keyway or Dowe

Question 43

If the physical distance between crank and cam is too great what's in between

Answer 43

An idler gear that does not affect speed relationship but does change direction of rotation

Question 44

Timing chains are used on both in block and overhead cam applications what are two types of chains

Answer 44

Silent type chain for light and medium duty and roller type chain for heavy duty applications

Question 45

On four stroke cams intake and exhaust lobes are offset. what is this referred to as

Answer 45

Lobe separation angle

Question 46

What is one of the most critical steps in reassembling an engine

Answer 46

Timing the camshaft

Question 47

Incorrect camshaft timing will result in what four things

Answer 47

Altered valve opening and closing points, poor engine performance, damage to engine components due to physical contact, alter fuel injection timing on engine camshaft actuated injectors

Question 48

What other engine accessories may the camshaft gear drive

Answer 48

Fuel injection pump,oil pump, water pump,accessory drives and balance shafts

Question 49

What may be used on the camshaft drive gear instead of multiple timing marks

Answer 49

Some engines use offset keys to change the camshaft timing