Camshaft and Follower Fundamentals

Question 1

Camshaft

Answer 1

Is a shaft with a series of eccentrics or lobes that control the opening and closing of valves

Question 2

Camshaft motion transfer

Answer 2

Changes rotary motion into reciprocating motion

Question 3

Camshaft nose

Answer 3

Usually the front of the shaft, a mounting surface for the camshaft drive gear or sprocket

Question 4

Camshaft journals

Answer 4

The load bearing surfaces that support the cam in cylinder block or head

Question 5

Camshaft lobes

Answer 5

The eccentrics that convert rotary motion into reciprocating motion of the cam follow

Question 6

Valve lobe profiles

Answer 6

usually higher point with a shorter effective duration, will vary in shape depending on engine horsepower, speed of operation and air induction of engine

Question 7

Injector lobe profiles

Answer 7

Usually shorter with a longer duration, vary depending on the design and requirements of the fuel injection system

Question 8

Cam lobe nose

Answer 8

The very top of the camshaft travel and is the point of maximum lift

Question 9

Cam lobe ramp (flank)

Answer 9

is the slope that the cam follower rides up and down on as the camshaft rotates

Question 10

Cam lobe base circle

Answer 10

base diameter of the lobe, at this point there is no valve opening

Question 11

Cam lobe lift

Answer 11

The distance the cam follower moves up as the shaft rotates

Question 12

Cam lobe duration

Answer 12

The number of degrees between the point where the valve opens and the point where the valve closes.
Is measured in crankshaft degrees
Normally different for intake and exhaust valves

Question 13

Camshafts are manufactured in one of 3 ways

Answer 13

Casting
Machined or forged from an alloy steel billet
Assembled from components

Question 14

Where are cast camshaft used?

Answer 14

Most commonly used in low horsepower, light and medium duty diesel engines

Question 15

What are two common camshaft locations

Answer 15

In-block

Overhead

Question 16

Overhead valve engines (OHV)

Answer 16

Engines with the camshaft in the cylinder block and the valves in the cylinder head

Question 17

Cam in-block

Answer 17

Camshaft motion is transmitted through the cam followers and pushrod to the rocker arm, the rocker pivots on a shaft and transmits cams motion to the valve

Question 18

Camshaft bearings - Bushings

Answer 18

bushings that are retained by a press fit in the cylinder block cam bores

Question 19

Cam lubrication

Answer 19

Bearings are lubricated through galleries on the block to bearings, lobes are also lubricated by splash off of the valve operating mechanism

Question 20

3 basic types of cam followers

Answer 20

Solid
Roller
Hydraulic

Question 21

Solid type cam lifters

Answer 21

form a solid link between the cam lobe and the valve operating mechanism. Straight body and mushroom type are two types of solid lifters. Mushroom type built to handle higher contact pressure

Question 22

Roller type cam lifter

Answer 22

either be solid or hydraulic design. Rather then being flat bottomed, bottom is equipped with a wheel or roller

Question 23

3 advantages of roller type lifters

Answer 23

Reduce frictional losses in the engine
Can handle much higher operating loads
Allow a quicker rate of valve opening and closing than solid type followers

Question 24

Camshaft drive

Answer 24

Gear drive is the most common, gears may be helical or spur-cut and are usually made of cast or forged steel. usually either bolted or pressed onto the front of the cam and indexed by and keyway of dowel

Question 25

Lobe separation angle

Answer 25

the offset between the centrelines of the intake and exhaust valves

Question 26

Incorrect camshaft timing will result in:

Answer 26

Altered valve opening and closing points
Poor engine performance
Damage to engine components
Alter fuel infection timing on cam actuated injectors

Question 27

Camshaft gear may serve as a drive for other engine accessories such as:

Answer 27

Fuel injection pump
Fuel transfer pump
Oil pump
Tachometer

Question 28

Why would a camshaft be assembled from components or in sections?

Answer 28

Permit ease of manufacturing and service

Question 29

Engines with cams in the block require what to transfer force from cam follower to the rocker arm?

Answer 29

Pushrod(s)

Question 30

To control endplay, most diesel engines camshafts utilize a_______ or ________?

Answer 30

Thrust plate

Washer

Question 31

Valve clearance is necessary with solid type follower to:

Answer 31

Allow for expansion of components as engine temperature increases