Chapter 19 Autos

How does switching between cam lobes happen - 1st way

By sliding pin that locks 2 cam followers together at higher rpms - when pin's removed, mild lobe operates cam follower to open and close valve

flame front... --- --- of the burning air-fuel mixture in the combustion chamber / has --- distance to travel in --- which gives rapid and effective combustion

FRONT EDGE of the burning air-fuel mixture in the combustion chamber / has LESS distance to travel in HCC which gives rapid and effective comb.

lift and duration in street engines

For street engines, too much lift or duration may not be beneficial because resulting lower intake manifold vacuum causes engine to idle roughly

GDI functions

Gas direct injection cylinder head / gasoline injected directly into the combustion chamber just above the piston / mixes fuel-air in the combustion chamber instead of intake manifold / spray fuel into combustion chamber during intake stroke and use fuel to actually cool incoming air, which increases its density and resistance to detonation / Other GDI systems cana spray fuel on intake stroke and near top of compression stroke, thus preventing detonation and allowing a lean air-fuel mixture to be burned by concentrating sprayed fuel very close to spark plug / can improve fuel economy up to about 35% and reduce emissions, especially carbon dioxide

cylinder head shapes... --- cylinder head and combustion chamber / --- - --- cylinder heads / --- cylinder head and --- --- / --- cylinder head and --- --- / --- --- --- cylinder head

HEMISPHERICAL cylinder head and COMBUSTION CHAMBER / PENT-ROOF cylinder heads / OVAL cylinder head and COMBUSTION CHAMBER / WEDGE cylinder head and combustion chamber / GAS DIRECTION INJECTION cylinder head

detonation

If velocity of flame front isn't fast enough, pressure building up in combustion chamber causes remaining gases to spontaneously ignite, which is called detonation / condition where remaining fuel charge fires or burns too rapidly after t initial combustion of the air-fuel mix. It's audible through combustion chamber walls as knocking noise / creates second flame front that collides with the first flame front / Extreme detonation can damage engine by concentrating high temperatures and pressures, which can melt a hole in the top of the piston

intake valves size compared to exhaust

In most cyl heads, intake valves larger than ex valves. / with multi-valve heads, intake valves may be smaller than ex valves bc there are more / ex usually smaller bc removing exhaust gas easier bc piston creating pressure as it moves up cylinder

valve face angles

In some cases, intake valve angles are different than ex valve angles / usually 45 or 30 degree / differences in angles represent manufacturer's engine design; exact angle has minimal effect on cylinder head function as long as valve and seat fit tightly enough to seal force of combustion in chamber

PCM

PCM also must know oil temperature to ensure oil viscosity isn't too thick or thin. Based on input from oil temp. sensor, the PCM either allows or disables variable valve timing; the viscosity of oil must be correct for accurate valve timing. The PCM must know the amount of engine load to determine the need for an advance or retard of cam timing / relies on feedback to ensure that the cams are rotating as commanded

cam timing solenoid

PCM is delivered to cam timing solenoid / cam solenoid allows oil pressure to move into cam phaser. / solenoid is turned on and off with a pulse-width modulation (PWM) signal / The longer solenoid device is turned off, the less it opens; the longer it's turned on, the more it opens, so the solenoid can regulate amount, and direction, of oil flow to cam phaser to alter camshaft/valve timing

To calculate engine load...

PCM primarily uses following inputs mass airflow sensor or manifold absolute pressure sensor / throttle ar temp. sensor / engine coolant temp. sensor / crankshaft position sensor

SOHC

Single Overhead Cam Engine / valve train works w/ 1 camshaft mounted either between rows of intake and exhaust valves on cross-flow heads, or directly over top of valves on non-cross-flow heads /

Timing gears rarely jump time, but if the timing chain or belt breaks, serious engine damage could result, depending on if it is a freewheeling engine or an interference engine. - (true or false)

TRUE

basic types of valve seals

Umbrella-style valve stem seals / O-ring valve stem seal / positive valve stem seal

valve spring closed pressure

Valve spring specification / measure of amount of pressure spring exerts on valve to close it tightly against valve seat / dependent on type of engine valve train / measured in pounds or kilograms

ability to control the advance and retard of the cam timing is...

a huge benefit to engine performance

cam phasers

actuators / advanced or retarded through the use of cam phasers / typically takes place of standard cam gear or pulley and uses engine oil pressure to move camshafts (advance and/or retard) when commanded by powertrain control module (PCM) / If oil pressure is held constant, cam phaser will hold cam timing constant / uses mechanical stop to limit maximum valve timing advance or retard.

duration specifications

advertised duration and duration at 0.050" lift

If we keep intake valve open after BDC

air continues to rush in because of the inertia of airflow

soft plugs

aka core plugs / plug the holes left over from the casting process / used to be freeze plug, but inaccurate / never designed to prevent damage by popping out during a freeze

camshaft profiles

aka grind / different camshaft profiles create different engine operating characteristics / Valve lift, duration, lobe separation, and overlap are features determined by the grind (profile) of the camshaft

wafers

aka spacers/pucks / replaced to obtain proper valve clearance between camshaft and valve stem / come in different thicknesses to achieve correct valve clearance.

valve stem seals

allow only enough oil pass to lubricate valve guide / some older engines do not have exhaust valve stem seals / used on both the intake and exhaust valves / fit around valve stem and usually seal to top of valve guide /

Keeping peak temp. below 2500°F (1371.1°C) ...

allows for the elimination of the exhaust gas recirculation valve on some vehicles

principle of air flow

allows the intake valve to be left open even when the piston is starting back up in the cylinder

If the cylinder head uses a bolt-on _____ cap as a bearing, then a machinist can remachine the bore to its original size, but the camshaft will sit just a bit lower in the head, which can affect valve timing.

aluminum

duration

amount of time valve stays open, given in degrees of rotation of the crankshaft / longer valve held open, more time there is for air to enter the cylinder / Higher-duration camshafts usually used in engines that operate at higher rpm / specification engineers use when designing cam lobe

lift

amount valve will open. The more valve lifts off seat, the more air can get into/out of engine / how far cam lobe will lift the lifter, cam follower, or bucket lifter / greater the lift, further the valve opens, and easier it is for air to enter cylinder / greater the lift, faster the valve has to move from closed to open, and harder the valve springs have to work at closing valve / amount lifter or cam follower moves with cam

valve moves back and forth inside guide----

approximately 21 times a second at 2500 rpm, so lubrication is critical to reduce wear on guide and stem

combustion chamber

area of an engine in which the air-fuel mixture is burnt. It consists of the bottom of the cylinder head and the top of the piston / inside engine / generally formed into cylinder head by casting process, movable floor is piston top / its efficiency determined by design including shape, valve positioning, and piston top shape

ram effect (intake stroke)

as column of air flows into combustion chamber (intake stroke), it creates inertia, which keeps air flowing until inertial energy is spent / intake valve begins open slightly before TDC / exhaust valve still open past TDC (overlap), w/ exhaust gases rushing out; this helps provide scavenging effect / All airflow happening in engine, whether in or out, is helped by the column inertia effect

The cylinder head components are... bare cylinder head ---- - at ----, this is the base onto which all other --- are --- / --- valves / --- valves / valve --- / valve --- / valve --- / valve --- --- / --- --- / --- / --- / --- ---

bare cylinder head CASTING- at CORE, base onto which all other PARTS are ATTACHED / INTAKE valves / EXHAUST valves / valve SPRINGS / valve RETAINER / valve KEEPERS / valve STEM SEALS / ROCKER ARMS / PLUGS / CAMSHAFT / CAM SEALS

cylinder head components bv

bare cylinder head casting- at core, base onto which all other parts are attached / intake valves / exhaust valves / valve springs / valve retainer / valve keepers / valve stem seals / rocker arm / plugs / camshaft / cam seals

cam lobe profile

base circle takes up about half of the entire profile / nose is the highest point of cam lobe and determines how far valve opens / cam duration built in and can't usually be changed while engine is running

why do exhaust valves heat up faster than intake

bc open when gases expelled from exhaust and gases flow around it, and cool intake charge flows around intake valve on intake stroke

contact cement

been used on valve cover gaskets, fuel pump gaskets, and intake and exhaust manifold gaskets

Technician A says that variable valve timing allows the engine to operate more efficiently and with more power over a larger range than with a standard fixed-valve timing engine. Technician B says that the use of variable valve timing (VVT) enables some manufacturers to eliminate exhaust gas recirculation (EGR) valves. Who is correct?

both

interference angle

built-in differences in angles between valve seat and valve face to provide quick bedding-in of valve face to valve seat on new engines; usually must be machined between about ½-1 degree from each other for sealing purposes /

How does switching between cam lobes happen - 2bs way

by using 2 cam lobes, but only one cam follower for each valve - cam lobes free to slide sideways to line up with cam follower / pair of solenoids operate plungers, which drop down into slotted ramps to push cam lobes in one direction or/other / cam lobes held at either extreme by spring-loaded detent assembly / Each plunger only remains in slot for about half a revolution of camshaft, just enough to push lobes to one side/other. Each plunger used to push lobes 1 direction.

non-cross flow heads

cam may be positioned right over top of valves and operate them through a bucket lifter, which may also have built-in lash adjuster / design makes for very compact valve train, although it calls for a more extensive cam drive as well as the need for enhanced oiling at top of engine for the camshaft, lifters, and followers

In an OHC type of engine, if the OHC cylinder head's deck surface is warped, it is likely that the ____ is also warped.

camshaft bore

valve seals

can allow oil seep down stems and puddle in port, causing puff of blue smoke during start-up / In engine with proper valve guide clearance, oil leakage reduced, but not eliminated

method of preventing lifter from rotating in the lifter bore

can be accomplished by connecting 2 adjacent lifters together with a pivoting link, or it could use a pin on the side of the lifter that rides in a groove in the lifter bore of the block or head

flat tappet valve lifters

can be solid or hydraulic / has nearly flat surface riding directly on camshaft lobe / slightly offset to one side of cam lobe causing lifter to rotate as it rides up lobe, instead of sliding up lobe - rotating action reduces friction and spreads out wear over face of the lifter

Generally, sodium-filled valves ...

can't be repaired and must be replaced when problems occur

Generally, sodium-filled valves....

cannot be repaired or ground and must be replaced if problems occur

cast rocker arms

cast in a die with molten metal / Metal alloys can be used, making cast, forged, or billet rocker arms that are more durable than their non-alloy counterparts / generally used in sports cars and other high-performance vehicles

valve tensile failure

causes valve to stretch be pulled apart by action of the valve spring / when first occurs, it generally causes valve stem to stretch, resulting in cylinder misfire due to loss of compression from valve not fully closing. In extreme case, it causes head to separate from stem and drop into combustion chamber, causing catastrophic engine damage

Before using sealant...

check vehicle manufacturer's service information to be sure product can be used with your application

ram effect

column inertia / Increased valve overlap and lift increase top-end rpm power due to ram effect / greater at high rpm so more air can be pushed into engine if valve is held open later in four-stroke cycle allowing timing to be tailored for distinct engine purpose (peak torque rpm range)

At cranking speeds, there isn't much -----------, so having ----- for a long time reduces engine intake vacuum and makes engine difficult to start bc --------/ w/ no ---------, leaving --------- during initial portion of --- stroke effective compression.

column inertia / valve open / intake air moves back out past intake valve as piston travels up on compression stroke / column inertia / intake valve open / compression / lowers

cylinder head design... combustion chamber inside --- / today's are designed to improve --- and --- of fuel mix, helping mix, and preventing --- --- from settling on --- --- surfaces

combustion chamber inside ENGINE / today's are designed to improve SWIRL and TURBULENCE of fuel mix, helping mix, and preventing FUEL DROPLETS from settling on COMBUSTION CHAMBER surfaces

hemispherical cylinder head look and history... combustion chamber that's --- in shape with valves in --- - --- arrangement and spark plug near --- of cylinder head directly --- top of piston / been around since approximately 1901 / Pipe, a belgian caremaker, made many early designs in 1905 / In early 1960s, Chrysler Corporation trademarked name Hemi™, which is perhaps most widely known h.c.c engine created

combustion chamber that's SEMICIRCLE in shape with valves in CROSS-FLOW arrangement and spark plug near CENTER of cylinder head directly OVER top of piston / been around since approximately 1901 / Pipe, a belgian caremaker, made many early designs in 1905 / In early 1960s, Chrysler Corporation trademarked name Hemi™, which is perhaps most widely known h.c.c engine created

pushrod ends

come in several different styles: ball to ball, ball to cup, and ball to adjustable tip

GDI timing

computer has control of the amount and timing of the injection sequence / varies based on a variety of engine conditions, such as engine load, speed, and temperature /

scavenging effect

condition caused by moving columns of air, which create a low-pressure area behind them, resulting in pulling force used to pull remaining burned gases from combustion chamber / Valve timing affects the amount of scavenging effect an engine has

valve float

condition occurring when valves moving so fast that spring tension is not great enough to fully seat valves as designed / valves can't be closed (sealed) by valve springs as fast as needed before next stroke / can allow piston to hit open valve on some engines

hydraulic valve lifters

constructed as a centrally located plunger inside a hollow cylindrical body / Engine oil fills inside of lifter body, pushing plunger up until all play in valve train is removed / are self-adjusting, so can automatically accommodate changes caused by wear or temp. fluctuations / more frequently used today bc they're quieter and require no periodic maintenance

stamped rocker arms

"stamped" from a piece of metal. They are not a high-strength or high-horsepower rocker arm and are intended for regular passenger vehicles

EPDM

(ethylene propylene diene monomer [M-class] rubber).

It is important not to have ----- strong valve springs

---overly---- / (too much pressure) - excessive pressure could cause premature wear on other valve train components / especially true for cam lobes and lifters as well as pushrods and rocker arms

Tech A says the gas direct injection (GDI) cylinder head design uses the fuel injected to cool the incoming air. Tech B says GDI engines use substantially more fuel than non-GDI designs. Who is correct?

A

oval combustion chamber... aka --- / oval shaped, like an inverted antique --- / valves are mounted --- and are --- --- ---, making the valve train --- in its design / On some newer designs, surface of head --- piston and forms --- --- areas: large area near the --- --- and smaller one on --- ---

AKA BATHTUB / oval shaped, like an inverted antique BATHTUB / valves are mounted VERTICALLY and are SIDE BY SIDE, making the valve train SIMPLE in its design / On some newer designs, surface of head OVERLAPS piston and forms TWO SQUISH AREAS: large area near the SPARK PLUG and smaller one on OPPOSITE SIDE

cam timing

Advancing cam timing closes intake valve sooner, giving more cranking compression, again because of low column inertia resulting in more torque and power in low rpm range. Retarding cam timing closes intake valve later giving more torque and power at higher rpm range / Cam timing adjusted according to what PCM desires based on input sensors

After-market timing gear

Aftermarket performance companies manufacture crank gears w/ offset keys or keyways that allow cam to be advanced or retarded manually to gain additional power at desired rpm

Variable valve timing using separate lobes for each valve

At low rpm, mild lobe actuates valve, allowing good low rpm power / At some point in rpm range, PCM causes aggressive lobe to actuate valve, improving higher rpm power

solid lifter

constructed as a hollow cast iron cylinder, capped on both ends / function by transferring action of cam lobe to pushrod / no means for changing length of solid lifter, unlike in oil-filled plunger action of hydraulic lifter, so they can't self-adjust to changes caused by wear or thermal conditions. As a result, all adjustments must be performed manually / require frequent valve adjustments / typically noisier than hydraulic lifters / can be made lighter than hydraulic lifter, so can be used at higher engine rpm without contributing to valve float.

iable cam timing

controlled by the PCM / several inputs used to ensure that ECM is able to control timing accurately / inputs are same inputs used by PCM to control fuel delivery and ignition system timing

valve timing

critical to proper operation of ICE / Many performance gains can be made by changing valve timing, but it all depends on what rpm range power is desired to be / affects amount of scavenging effect engine has / controlled by physical shape and position of cam lobes on camshaft / In past applications, engine designer would have to decide which valve timing best served engine operating range then design camshaft for that purpose.

hemispherical cylinder head functions

cross-flow cylinder head / air-fuel mixture enters on one side, and exhaust gases exit out the other side / Positioning valves with spark plug just off center of combustion chamber leaves more room for relatively large valves and ports, helping engine breathe / air-fuel mixture starts to burn at the plug and then continues burning outward in all directions - flame front called flame propagation / limited to 2 valves per cylinder

valve sizes....

depend on engine

concentricity

describes valve seat where valve seat and valve stem share a common center. In this design, valve can seal against seat no matter how rotated

valve train configuration

determined by manufacturer, so in variety

cam lobe

determines when each valve opens, how far opens, and how long stays open - all determined by cam lobe profile / raised portion on camshaft; used to lift lifter and open valve on usually round shaft / can be moved forward or backward in relation to crankshaft position to make events happen sooner/later in piston stroke

Peak engine torque

developed at peak volumetric efficiency.

sealants design

diff sealants for diff applications / applications in which sealants can't be used /

valves

diff. sizes / experience enormous stress even in normal conditions / opening and closing controlled by camshaft lobe and valve spring / control flow of air and fuel into and out of cylinder /

lobe lift

difference between base circle and nose

piston stroke

distance piston travels through engine cylinder from top dead center to bottom dead center and vice versa

During the intake stroke, a drop in --- occurs as the piston moves down the cylinder during the --- stroke / --- --- pushes --- and --- through the --- ----, filling the void where the piston was

drop in PRESSURE occurs as the piston moves down the cylinder during the INTAKE stroke / ATMOSPHERIC PRESSURE pushes AIR and GAS through the INTAKE MANIFOLD, filling the void where the piston was

advertised duration

duration specification / measures duration from where lifter first starts to move

duration at 0.050"

duration specification / measures duration starting when lifter hits 0.050" / better indicator of camshaft profile and how it affects engine operation / bc by 0.050", cam is well into its lift profile

OHC engines

each valve has 1 rocker arm and 1 lobe on camshaft / rocker arm comes in diff rocker arm ratios depending on engine design / use camshaft followers instead of rocker arms / intake valves usually on 1 side of cylinder head and exhaust valves on other side, with camshaft sitting between them / Rocker arms or cam followers would be between camshaft and valves on each side of camshaft

in vehicle drive at 2500 rpm...

each valve opens and closes at around 21 times per sec.

in vehicle drive at 6000 rpm...

each valve opens and closes at around 50 times per sec.

camshaft lobe

eccentric "egg-shaped" portion of camshaft that pushes on valve lifter or camshaft follower / controls valve opening and closing / shape affects power characteristics of engine / If cam is single cam with exhaust and intake lobes, then both intake and exh are affected by rotating camshaft to advanced or retarded position / pushes the rocker arm up on one end, and the other end pushes the valve down to open

lip seal

effective at sealing low pressures, but differential speed between opposing surfaces can be substantial / As lip-type seal wears, garter spring holds tension on seal, keeping it against part it's sealing

In naturally aspirated engine...

engine relies totally on atmospheric pressure to push air into cylinder

Any oil burned in the combustion chamber or exhaust system will result in...

excessive oil consumption, which appears as a bluish-white exhaust smoke

EGR

exhaust gas recirculation

exhaust valves

exhaust gases exit comb chamb through these/ exhaust gases pushed out by piston, creating greater force on exhaust gases than atmospheric pressure pushing air into cylinder / oil can be pulled past ex valve stem during deceleration like intake valve /

ram effect (exhaust stroke)

exhaust valve begins to open shortly before piston reaches BDC allowing remaining pressure in cylinder to escape before piston starts moving back up / allows time for exhaust valve to open far enough so at higher rpm, there's time to fully evacuate cylinder / When piston travels back to TDC, exhaust gases pushed rapidly out of cylinder, causing column effect in exhaust system

O-rings design / placement

fit in shallow grooves cut in head around cylinders and passageways to seal compression and fluids / crushed in place when head bolts are torqued into place / fit in grooves, so very effective, but expensive way to seal heads / rounded ring of rubber or plastic

Umbrella-style valve stem seals

fit tightly around top of valve stems and ride up/down w/ valves / umbrella larger diameter than valve guide, so oil drips off umbrella outside of guide - hence seal prevents excessive oil from leaking into guide / generally found on older (1980s-) American-built V8 engines / not typically in modern engines

L-head

flat head / four-stroke ice with both intake and exhaust valves in one side of engine block, which are operated by lifters actuated by single camshaft / sometimes called flat head because there no valves in head

The most popular adhesive to hold gasket in place...

form of contact cement coming in either aerosol can or squeeze tube / capable of adhering to diff surfaces, like felt, cork, metal, paper, rubber, and asbestos gaskets

flame front

front edge of the burning air-fuel mixture in the combustion chamber / has less distance to travel in HCC which gives rapid and effective comb.

inert gas

gas that will not react chemically / doesn't burn

anisotropic

gasket designed to conduct heat laterally to transfer heat from combustion chamber to coolant faster / normally constructed with a steel core

gaskets made by/of...

generally designed to be single use / can be made of soft materials like cork, paper, or various of rubbers / can be made of soft alloys and metals like brass, copper, aluminum, and stainless steel - such materials may be used individually or in some cases as blends to produce required functional material / with use reduction of asbestos, enhanced gasket materials have been developed / modern gaskets must be made of more robust materials, like vulcanized rubber or EPDM / manufacturers are producing improved material combinations such as nitrile-cork blends to deal with the extreme demands placed on modern engines

control module

generic term identifying electronic unit that controls 1+ electrical systems in vehicle; also called control unit

aluminum alloy

good for light weight / conducts heat away from the combustion chamber more rapidly than cast iron / with an aluminum-alloy head, the heat of combustion can be conducted to the coolant faster, reducing the chance of localized hot spots / engine efficiency is reduced when heat is removed too quickly from combustion chamber, so aluminum cylinder heads may be designed with smaller water jackets to prevent them from overcooling the engine

If exhaust valve is held open later, then it will ---- into the ------, which can result in exhaust gases being -------the engine. This ---- the incoming air-fuel mixture with inert exhaust gas to help reduce -------

hang open / intake stroke / pulled back into / dilutes / oxides of nitrogen emissions

valve keepers are ----- to withstand ---- action of --------

hardened to withstand pounding action of valve opening and closing

ball-to-cup pushrod

has smooth, rounded ball at one end that sits in a cup on valve lifter and a cup at other end into which a smooth, rounded ball end of rocker arm assembly fits.

gasoline-proof hardening sealants

have little to no "give" once dry and only used in extreme situations like to help hold a cracked component together when new component isn't available

dual camshafts

having allows intake and exhaust valve timing to be controlled separately from each other, which can reduce emissions, increase power, and increase engine efficiency or mileage

________ orfices control the flow of coolant between the engine block and the cylinder head.

head gasket

sealing beads

help eliminate leak paths / in MLS

valve guides

hollow metal passageways in cylinder head in which stem of valve rides / allows valve to move only up and down while holding in same position side to side / must be able to retain lubrication for valve stem to live long / can allow oil seep down stems and puddle in the port, causing puff of blue smoke during start-up

With government air quality standards constantly rising, achieving a cleaner burn for an internal combustion engine means...

hotter burn, higher pressure, and thus a more intense combustion process / Valves, valve seats, pistons, and cylinders all have to meet increased demands.

stem wear

if bad enough, can cause intermittent loss of compression and misfires. Also, oil will be drawn down intake valve guides, causing oil to enter intake airstream / oil will also seep down exhaust port when engine is off, or be drawn past exhaust valve stem during engine deceleration

valve guide clearance

in engine with proper valve guide clearance, oil leakage is reduced, but not eliminated /

pushrod engines

in many, valves positioned in line on 1 side of cylinder head and pushrods on other side of head, with rocker arms between them / To aid in mounting and aligning all rocker arms, the r.a. may be mounted on common rocker shaft

garter spring

in oil seal / applies small, constant pressure to keep sealing lip in contact with rotating part it is sealing

aftermarket performance camshaft

includes specifications card used during engine assembly to ensure correct timing

OHV engines

incorporate pushrods / each valve has one lifter, one pushrod, one rocker arm, and one lobe on the camshaft dedicated to its opening and closing

air-fuel mix turbulence is... increased in the ---, aka ---, area, which is the area between the --- head at --- dead center and the --- head / the name comes from the --- of the air-fuel mixture into a small "---." / piston --- the air-fuel mixture and forces it with great --- out of the --- area, creating turbulence, which helps to thoroughly --- --- fuel and --- air / it takes certain amount of --- to maintain good turbulence

increased in the QUENCH, AKA SQUISH, area, which is the area between the PISTON head at TOP dead center and the CYLINDER head / name comes from the SQUISHING of the air-fuel mixture into a small "CHARGE." / piston SQUEEZES the air-fuel mixture and forces it with great SPEED out of SQUISH area, creating turbulence, which helps to thoroughly mix HEAVIER fuel and LIGHTER air / takes certain amount of SPEED to maintain good turbulence

air-fuel mix swirl was initially created by the --- and --- of the --- port.

initially created by the SHAPE and ANGLE of the INTAKE port.

valve overlap

intake and exhaust valves are open at same time / High-performance engines have more degrees of valve overlap than street engines bc longer cam duration / In reality, even standard camshaft grinds (valve timing) include some valve overlap at TDC / in traditional engine designs, camshaft design and valve timing are compromise for street engine use

why intake valve more likely to pass oil through guide than ex valve

intake port has low manifold pressure (vacuum) bc intake stroke, especially during deceleration when coasting downhill

bc inert gas doesn't burn...

it causes combustion gases to burn more slowly, which reduces peak combustion temperature - Keeping peak temp. below 2500°F (1371.1°C) reduces amount of oxides of nitrogen, or NOx

As air flows into the cylinder...

it gains velocity in the intake manifold, which creates a column of air that has inertia and keeps the airflow moving, or racing, into the cylinder

cam seals

keep oil from leaking past rotating camshaft

rocker arm

lever actuates valve by pivoting near center and pushing on valve stem tip to open valve, resulting in a change of the direction of movement / can be used on OHV or OHC engines

cam lobe specifications

lift / valve duration

plugs

like seals, used to block off passages where oil and coolant flow / primarily used to block holes used in original casting and machining of head

valve seal or camshaft seals are..

lip-type dynamic oil seal

cam lobe centerline

location of cam lobe in relation to TDC of engine in degrees

valve stem

long shaft-like portion of valve assembly allowing valve to move freely inside valve guide and contains valve groove(s) into which keeper's inserted

pushrod

long, often hollow, metal tube that transfers force from valve lifter to rocker arm assembly

pushrods

long, often hollow, metal tube that transfers force from valve lifter to rocker arm assembly, but designs vary / ex is diff length than intake

valve seat inserts

made of metal rings that match shape of valve face to form strong & complete seal / usually made of an iron alloy because the alloy is stronger than iron itself and provides a more durable surface /

exhaust valves manufacturing

made of nickel-based alloys to help withstand extreme heat / if too hot, can melt, or will deform sealing surface of face as it slams closed, resulting in burned valve and loss of compression / some manufactured have hollow stems 1/2 filled w/ sodium during manufacturing process to help transfer heat away from valve head

valve cooling

majority of the valve cooling happens when hot valve face sits in cooler valve seat in head / some cooling takes place through stem and across into valve guide

caution when using RTV silicone is to...

make sure to use oxygen sensor-safe RTV on engines equipped with oxygen sensors bc regular RTV gases will be drawn through PCV system and burned in combustion chamber / resulting burned silicone gases then coat surface of oxygen sensor, rendering it inoperative.

Usually in engines that operate at high rpm...

manufacturer uses multiple springs to close valve to increase spring pressure and prevent valve float

roller rocker arms

many manufacturers use roller rocker arms on their engines to push fuel efficiency / Roller rocker arms use rolling pivots at valve end and center of rocker arm / rolling action at pivot points reduces friction and wear on rocker arm / reduced friction gives small increase in fuel efficiency and performance

in case of canted valves, the rocker arms...

may be individually mounted to the cylinder head

bucket (style) lifters features/location/parts

may have built-in lash adjuster or be mechanically adjusted / design makes adjusting and servicing valves more difficult bc camshaft usually must be removed to gain access / used if camshaft is on top of and centered over valves / have lifter assembly mounted on top of valve and hollowed out (bucket-like) / hollow portion placed upside down over top of valve stem and provides a wear surface between camshaft and valve stem

valve spring open pressure

measure of amount of pressure valve spring is exerting to overcome inertia of valve train as valve reaches fully opened position / dependent on type of engine valve train / measured in pounds or kilograms

valve spring

metal coil spring that pushes valves to fully closed positions after being opened as cam lobe returns to its base circle/ compresses when cam lobe pushes valve open

Stellite

mixture of chromium and cobalt that can hold up to higher heat.

coil bind

more lift creates more pressure on valve train components due to pushing valve further and compressing valve spring further and too much lift can cause coil bind / occurs when coils of spring touch each other / causes the spring or the camshaft and lifter to wear excessively or break /

the lip-type dynamic oil seal

most widely used seal for rotating parts / uses a garter spring to help keep lip of seal in contact with shaft / seal with precisely shaped dynamic rubber lip held in contact with moving shaft by garter spring

flame propagation

movement of the flame from spark plug/through combustion chamber during combustion process

MLS

multi-layer steel (MLS) head gasket / wide range of benefits like strategically placed sealing beads, extra strong layers to provide superior combustion sealing, and stainless steel material that maintains shape despite thermal expansion and scrubbing between engine block and the cylinder head

To increase applied force over distance, ------ must be used

multiple or moveable pulley system / theory relies on the concept of mechanical advantage

mechanical advantage

multiplication of applied force through use of mechanical device / process using device to get more output force than amount of input force, with trade-off being that input distance is proportionately longer than output distance

valve head

mushroomed portion of valve containing face and margin

overall valve requirements

must be able to... take high temps. bc comb. temp and ex gases / resist spring pressure trying to pull valve apart and combustion pressure trying to force it into valve seat /

To lift engine block off floor, you.... To keep block suspended in air...

must pull down on rope with a force greater than weight of engine block / your exerted force must equal the weight of the block - mechanical advantage of this system is 1

most-late models

newer vehicles / require hardened seats in both intake and exhaust ports due to extreme temperatures and pressures that newer engines must handle /

Some applications require...

non-hardening gasket sealant so sealant will "give" when metal parts expand and contract under normal heating and cooling cycles

integral valve guide

non-replaceable valve guide bc constructed as part of cyl head / cast into cylinder head when cyl head is formed / machined into casting /

adhesive sealants...

not typically used on newer vehicle models

cam lobe separation

num. of degrees between centerline of intake lobe and centerline of exhaust lobe; this w/cam duration determines amount of valve overlap / Generally speaking, wider separation, better camshaft for building power at lower rpm / Narrowing separation builds power at higher rpm. / smaller number of degrees of lobe separation, the more valve overlap there is / specifications measured in crankshaft degrees, not in camshaft degrees

To seal the rotating parts of an engine...

oil seals are needed

OHV valve arrangements

one exhaust valve to a five-valve arrangement / three-valve arrangement usually has two intake valves and one exhaust valve / four-valve arrangement usually has two intake and two exhaust valves / five-valve arrangement usually has three intake and two exhaust valves

electronic module valve timing through use of camshafts w 2 lobes per valve

one mild lobe for low rpm, and one aggressive lobe for high rpm

lifter face-to-camshaft lobe contact is...

one of the highest load areas in the engine

valve train

operates off camshaft / all parts used in opening and closing valves / move air and fuel through engine / all parts between drive of camshaft and valves / all components driven from camshaft drive, including lifters, pushrods, rocker arms or cam followers, valves, valve springs, valve keepers, and valve retainers

closing ramp

opposite of opening ramp and allows valve to close properly / starts at the nose and ends at the base circle

OHV engine

overhead valve engine / valves in cyl head assembly over top of piston / valves operated by camshaft in cylinder block / 1 valve located on each camshaft lobe as camshaft rotates, lifter rises and transfers motion to pushrod, then pushrod moves rocker arm which pivots near center and pushes valve open / relatively simple design that is inexpensive to build / each valve has 1 lifter, 1 pushrod, 1 rocker arm, and 1 lobe on camshaft dedicated to its opening and closing

inertia causes air molecules to... pack together more tightly, especially at higher engine rpm, creating a ram-air effect

pack together more tightly, especially at higher engine rpm, creating a ram-air effect

valve seat

part of cylinder head which a valve seals (mates with face of valve) when valve is closed / either ground or cut (machined) into proper shape and concentricity so valve face and seat seal tightly /

camshaft

part of engine that activates valve train by using lobes riding against lifters / offsetting and using cam followers allows easier access to valves / only fitted in OHC and DOHC / provides force to open valves / shaft with offset eccentrics, called cam lobes / ground for specific applications / may/may not be symmetrical, meaning opening and closing ramps may/may not be identical

valve stem seal

prevent oil from entering the engine combustion chamber / pressed onto the valve guide / allows valve stem to be wiped almost clean of oil on opening trip, keeping minimum amount of oil pulled down between valve stem and guide, for lubrication purposes

insufficient spring pressure...

problematic bc causes valve float, which can allow piston to hit open valve on some engines

bedding-in

process of valve wearing into valve seat and creating positive seal around whole diameter during the initial breaking-in of engine / provides long-lasting, leakproof seal

"street cams," 3-quarter race, and full race cams have...

progressively more lift and duration, all tailored to meet operating conditions of engine

valve rotator in exhaust spring retainers...

provide rotation function to slightly rotate exhaust valve in one direction or other each time opened, thus preventing hot spots and carbon buildup, and evening out wear on valve face and valves / found only on exhaust valves bc intake valve is cooled by incoming fuel and air

retarded cam timing

provides greater engine torque when large amounts of air are flowing into the engine at higher rpm

PWM signal

pulse-width modulation signal / variable rapid (in milliseconds) time-based on/off switching of a DC signal / used to control outputs such as fuel injectors, shift solenoids, torque converter clutches, and even interior vehicle lighting

One of the ways to make engines run cleaner is to...

raise the temperature at which they operate / Today's cleaner engines run 30-40°F (-1.11-4.44°C) hotter than 30 years ago

rocker arm ratio

ratio refers to amount of movement on valve side of rocker arm in comparison with that on opposite side / most common ratios are 1.5:1, 1.6:1, and 1.7:1 / allow manufacturers to use smaller lift camshafts - camshaft with smaller lobes than needed to generate a specified amount of lift can be used because rocker arm ratio magnifies camshaft's lift

roller tip valve lifter

reduces this friction / can be solid or hydraulic / roller rolls along lobe with less friction / roller must remain in rolling contact with cam lobe, so lifter must incorporate a method of preventing it from rotating in the lifter bore / As camshaft turns, roller rolls over surface of camshaft / lobes push followers away, transmitting movement to valve and pushing it down (open)

newest cam phaser

relies on an electric motor-driven phaser to vary the cam timing / more accurate, bc it doesn't rely on oil being a consistent viscosity or squeaky clean

integral valve guide repair

repaired by reaming it oversize and installing thin wall bronze liner / Once installed, inside of liner is burnished by forcing a specially sized ball bearing through it / machinist can by using head shop to machine valve guide (boring out) oversize and then installing thick wall guide, which can be made of iron or bronze / guide then machined to proper size / must be repaired when valve guide has worn past service limits

non-integral valve guide

replaceable valve guide / manufactured separately from cyl head and press fit into specially machined hole in cyl head that was formed as head was cast / can be removed and replaced, as needed, when excessively worn / typically made of cast iron or bronze / has interference fit to cylinder head and usually driven into place by using valve guide driver and air hammer or small sledge hammer

valve stems

require small amount of running clearance as well as small amount of lubrication / possible for excessive amount of oil to leak past valve stems into intake and exhaust ports

Early Hemispherical Combustion Chamber drawbacks

required complex valve train design that included two rocker arm shafts per head, with uneven rocker arm lengths - was overcome by using OHC design

gasket functions

required to seal / One of the ways to make engines run cleaner is to raise the temperature at which they operate / modern gaskets must be made of more robust materials, like vulcanized rubber or EPDM / form seal by being compressed between stationary parts where liquid or gases could pass / Some gasket materials are designed to swell once they are put into service, thus increasing sealing ability / can't be used around a rotating part, like where camshaft protrudes through front of cylinder head, bc they would quickly wear out and leak.

valve spring retainer works w/ valve keepers to...

retain valve in cyl head / used along w/ valve keepers to hold spring in place on stem

cam lobe ramp

rise of lobe from base circle to top of lobe, which is where valve starts to lift - on side opposite of where it starts to close / degrees of rotation valve remains open and cam lobe separation are specifications measured in crankshaft degrees, not in camshaft degrees

cast iron or bronze

robust materials that can withstand process of being pressed or driven into cylinder head as well as provide durable surface for valve stem

cross-flow heads

rocker arms pivoting near center, or cam followers pivoting on one end, ride on each cam lobe and directly operate each valve / Some systems incorporate hydraulic lash adjusters right in the rocker arms or in the cam follower pivot so valve train will be self-adjusting

One of most popular types of sealants for gasket sealing is...

room temp vulcanizing (RTV) silicone

RTV

room temperature vulcanizing silicone / adhesive able to set, or "vulcanize," at room temperature / when applied, has consistency of a gel, and as it sets, becomes rubbery / should only be applied thick enough to fill gaps with small amount

oil seals

round seals made of rubber or rubber-type compound of silicone, EPDM, or another durable, flexible material, placed in metal housing / typically driven into machined bore around rotating part / metal spring, called a garter spring, is wrapped circularly around the inside of the seal / must be replaced when removed or when component is replaced

base circle (of the cam lobe)

rounded bottom part of camshaft (off the lobe/egg shape) where valves remain closed or at rest / When lifter is on base circle, valve is closed / where lifters rest when valves are closed

ball-to-adjustable screw pushrod

same as the ball-to-ball pushrod except there's a screw thread and lock nut near the end closest to the rocker arm that, when turned, lengthens or shortens the pushrod

head gaskets

seal and contain the pressures of combustion within the engine, between cylinder head and the engine block / seal oil and coolant passages between engine block and cylinder head / Special facing materials added to both sides of gasket core to provide comprehensive seal under varying expansion conditions / On some engines, head gasket provides or adjusts proper clearances between piston and cylinder head by thickness of the gasket / many have added silicone-based outer coating on both sides of material layers to provide additional cold sealing ability during start-up and warm-up

O-ring valve stem seal

seal used where valve spring retainer attaches to valve stem to seal juncture and prevent excessive oil from leaking into the valve guide / fit on top of valve in groove just below valve spring keepers / seals oil from leaking between valve stem and valve retainer / used primarily on General Motors V8 engines from the 1980s- / not typically in modern engines

sealants and gaskets

sealants are almost never applied to head gaskets / To aid gasket sealing, there are many different brands and types of sealants

valve seat recession

seats slowly wear away and sink deeper into head

aftermarket

segment of trade that supplies parts, services, and repair for vehicles outside of original equipment manufacturer (OEM) or dealer network

hydraulic bucket lifters

self-adjusting in the same manner as a standard hydraulic lifter and therefore do not require periodic maintenance

profile

shape

intake port

size and shape in the cylinder head can affect engine output by affecting the speed of the air flowing through the port / A. Small port = good low rpm torque. B. Large port = good high rpm torque /

exhaust port

size and shape in the cylinder head can affect engine output by affecting the speed of the air flowing through the port / A. Small port = good low rpm torque. B. Large port = good high rpm torque / typically is lightly pressurized while the engine is operating under load, so oil cannot be pulled in as easily

ball-to-ball pushrod

smooth and rounded at each end / One end fits into a "cup" or dished-out piece in valve lifter, and other fits into a cup in rocker arm assembly

DOHC engine

some engine designers use a phaser on exhaust camshaft only - phaser used with this engine is typically not intended for increased engine power, but for better exhaust gas recirculation

DOHC phasers

some engine designers use a phaser on exhaust camshaft only - phaser used with this engine is typically not intended for increased engine power, but for better exhaust gas recirculation / phaser can be installed only on the intake camshaft for greater engine power, or it can be installed on both the intake and the exhaust camshafts

spark plugs

some engines use 2 in combustion chamber - not common

exhaust valve spring retainers

some have built-in valve rotator

fire rings

some head gaskets incorporate these stainless steel rings to help contain heat and pressure within the cylinder / steel rings built into the cylinder head gasket / provide extra sealing on the top of the cylinder to help seal in the high-combustion pressures

keeper groove

specific notch in valve stem into which keeper fits securely

timing gear

sprocket attached to the crankshaft assembly and the camshaft assembly

If too much RTV used, it will...

squeeze out from between surfaces and form large globs on inside of engine that can break off and plug up oil pump screen, starving engine of oil

In high-performance applications, the intake and exhaust valves can be made of...

stainless steel or titanium, both of which are suited to extreme conditions

column air-flow

takes certain amount of speed to maintain good air-flow / If airflow is too slow, fuel will fall out of the air and not much ram air effect will be available. If airflow is too fast, the airflow will be restricted, which reduces the total amount of air-fuel mixture that can enter the combustion chamber / A. Small port = good low rpm torque. B. Large port = good high rpm torque

valve keepers

tapered devices keep valve spring's retainer attached to valve stem / valve retaining devices / usually semicircle / wedge-shaped pieces that lock into groove or grooves near top of valve stem to keep valve spring retainer and spring retained on valve while in head / aka valve locks / usually split taper matching valve retainer taper / protruding ridge or rings fitting into groove on valve stem

wedge combustion chamber

tapers away from the spark plug, which is at the thick end of the wedge / valves typically arranged in a straight line positioned along tapered angle, which puts them at an angle to the top of the piston / has smaller combustion chamber surface area than other types of cylinder heads, meaning less boundary area where fuel can't burn as easily, lowering hydrocarbon (unburned fuel) emissions / flame is directed toward small end of wedge, damage caused by detonation is reduced / wedge design speeds up the velocity of the flame front

The most widely used seal for rotating parts is...

the lip-type dynamic oil seal

Choosing which material and design to use depends on...

the substance to be sealed, the pressures and temperatures involved, and the materials the mating surfaces to be sealed are made of / best way to determine which gasket material is appropriate for an engine is to refer to manufacturer's service information

valve spring retainer

thick washer-shaped piece of metal positioned near top of valve stem / holds top of valve spring to keep pressure on valve while in cylinder head / tapered center hole keeping valve spring compressed between it and cylinder head and provides mating surface for valve keepers / usually made from steel / aluminum and titanium used in some high-performance engines

head gasket

thin metal sheet, often made of layers of different materials, with holes cut for piston openings and passageways for oil and coolant / seals cylinder head assembly to engine block / clamped between cylinder head and engine block with head bolts or studs / keeps combustion pressure, coolant, and oil inside proper areas / also distributes air and fuel into the engine's cylinders

twisted gear cam phaser

twisted gear arrangement and a return spring / When oil pressure pushes against gear mechanism, cam rotates and advances / When oil pressure is released, return spring brings cam back to fully retarded position / At rest, these types may be fully retarded or fully advanced

valve seat manufacturing

typically made of hardened steel to withstand extreme temps and pressures encountered during engine operation / must be compatible with today's gasoline / Use of today's unleaded gasoline in engine with non-hardened valve seats will cause seats to slowly wear away and sink deeper into head

GDI design

typically of the multi-valve pent-roof design with the spark plug centrally located and the fuel injector offset to one side / some manufacturers have been able to remove the throttle plate and control engine speed and power by controlling the fuel by itself, reducing engine's pumping losses of trying to pull air past throttle plate

forged rocker arms

use localized pressing forces to form a rocker arm from steel or a steel alloy / forging process enables metal to withstand extreme pressure, heat, and wear / used in high-torque, high-horsepower applications such as race cars and hot rods

thermostat housings

use o-rings instead of gaskets

poppet valve

used by vast majority of automotive engines / mushroom valve / called this because it "pops" up and down to open and seal its port / fits into a port in cylinder head / valve face makes a gas-tight seal against the valve seat / intake valve opens and closes intake port allowing air and fuel to enter combustion chamber and to seal it during compression, power, and exhaust strokes / exhaust valve covers exhaust port during intake, compression, and power strokes.

tetraethyl lead

used in gas before 70s / inexpensively boosts octane / Lead also lubricated valve seats by providing cushioning effect allowing valve seats to be machined into base cast iron material and still give good life / when installation of catalytic converters was mandated for emission control purposes in mid-70s, lead couldn't be used in fuel anymore bc lead would contaminate and kill converter. situation required use of hardened valve seats, which resist wearing out quickly.

Positive valve stem seals

used in today's engines / fits tightly on top of valve guide as valve stem moves up/down inside seal / most effective bc it forms positive seal between guide and valve stem / have small groove cut into top of seal that rides on stem - design keeps small amount of oil against valve stem and only allows very small film of oil past to lubricate guide / more positive seal than an umbrella or O-ring seal

valve arrangement (old)

used to be positioned valve head face up and in engine block on one side of cylinder - L-head (flat head)

sealants functions

used to seal two surfaces in stationary contact with each other, like between gasket and sealing surface of part being sealed / could be between 2 mating surfaces w/out gasket between them / .

theoretical valve timing

used when explaining operation of a four-stroke engine and assumes that valves open and close instantly at TDC and BDC / in reality, valves open sooner or later

advanced timing

useful when engine needs high torque during lower engine rpm operations

valve seat machining

uses a special hardened cutter to cut proper angles into seat

vane-type phaser

uses vanes like those in a vane-type oil pump to move camshaft / Oil pressure moves into phaser and pushes on 1 side of vane to advance cam timing / When oil pressure is switched to other side of vane, camshaft is retarded

valve springs

usually coil springs / return valves to fully closed positions and hold close / controls valve opening and closing / closes and holds valve against seat / valve can have 1+ per valve / 2 springs can close valve faster than 1 spring can.

canted valves

valve arrangement in cylinder head where valves are at angle to cylinder bore / Canting valves can make straighter path for air flow into/out of intake and exhaust ports / used in hemispherical-shaped and some wedge-shaped combustion chambers

Racing engines are designed with greater

valve lift, longer valve duration, and increased valve overlap in order to maximize the effect of column inertia encountered at higher rpm

part riding against cam lobe is...

valve lifter

tappet

valve lifter / device that transfers motion from cam lobe to pushrod or directly acts on valve and spring, depending on whether cam is in engine block or cylinder head / rides on camshaft lobe / transmits movement of lobe to pushrod / can be solid, requiring periodic adjustment, or hydraulic, which are self-adjusting

On turbocharged or supercharged engines, minimal ------ is typically used, as...

valve overlap / air forced into the engine by the turbo or supercharger would be forced out of the exhaust during overlap reducing efficiency

valve spring specifications

valve spring closed pressure / valve spring open pressure / spring installed height

spring installed height

valve spring specification / how tall spring is when everything is assembled in cylinder head / important bc spring length affects amount of pressure spring exerts on valve train

on variable valve timing engines...

valve timing can be modified to provide best operating conditions for engine speed, power, efficiency, and emissions / electronic module or separate cam lobes for each valve for variable valve timing / vvt primarily in OHC engines

on fixed valve timing engines...

valve timing is a mechanical setting, and once set, cannot be changed w/ physically changing timing components in some way / technician sets timing components to factory marks factory on crank and cam gears - critical that timing marks are correctly aligned when installing time components

valve components

valve tip / keeper groove / valve stem / valve head / valve face / valve margin

Newer engines have computer controlled -------that can adjust ------- while engine is operated

valve trains / valve timing

valve arrangement (modern)

valves in cylinder head above pistons (OHV)

OHV

valves located in cylinder head above pistons / several valve arrangements

valve designs

variations to suit the unique features of the engine into which they are installed / Some engines, like those in heavy construction vehicles, need valves with strength and longevity to handle long, grueling work / Other engines, such as those in a race car, require valves that are lightweight and capable of withstanding high stress situations, usually for shorter longevity

gasket adhesive

variety of different chemicals are available to hold gaskets in place during assembly and to aid in sealing /

non-hardening gasket sealants

very forgiving with gasket surfaces that are less than perfect / sealant will "give" when metal parts expand and contract under normal heating and cooling cycles

Because of inertia and the amount of time it takes the valves to fully open and close...

we have to begin the opening times earlier and delay the closing time, thus we begin intake stroke by opening intake valve as piston is still moving up and exhaust valve is still slightly open, but closing

opening ramp

what opens the valve / starts at the base circle and ends at the nose

cam specifications

when comparing them, it's important to know duration specification listings

valve seat grinding

when seat is ground to proper angle with special grinding stone.

intake valves

where fuel mix enters comb. chamb. / made of steel mixed with chromium or silicon to make more resistant to corrosion, and manganese and nickel to improve strength / has to withstand / spring pressure and combustion pressure / does not get as hot as the exhaust valve does / valve face may / must withstand spring pressure and comb press. / doesn't get hot as ex valve /

valve-to-piston clearance

with too much lift, not enough v-to-p clearance / Too much valve lift can cause valve to hit piston and ruin engine

overlap specifications

won't be given if you have DOHC engine because exhaust and intake lobes run on separate shafts

When inspecting a cylinder head, crusty flakes of material are found inside the combustion chambers, indicating:

worn valve guides or piston rings

Cylinder heads can have ------basic types of valve seals

1/3

electronic module valve timing

2 primary ways to using them: phasers / camshafts with 2 lobes per valve

valve lifters locations

4 different places: in engine block, cylinder head, rocker arms, or between cam lobe and valve tip (bucket style)

events in operation of any ICE

5 - intake of mix, compression of mix, ignition of mix, power stroke triggered by combustion of mix, exhaust of burned gases from combustion chamber

hemispherical cylinder head functions... --- - --- cylinder head / air-fuel mixture --- on --- side(S), and exhaust gases exit out the --- --- / Positioning valves with --- --- just off --- of combustion chamber leaves more room for relatively large --- and ---, helping engine --- / air-fuel mixture starts to burn at the --- and then continues burning outward in --- direction(s) - flame front called --- --- / limited to ---valves per cylinder

CROSS-FLOW cylinder head / air-fuel mixture enters on ONE SIDE, and exhaust gases exit out the OTHER SIDE / Positioning valves with SPARK PLUG just off center of combustion chamber leaves more room for relatively large VALVES and PORTS, helping engine BREATHE / air-fuel mixture starts to burn at the PLUG and then continues burning outward in ALL DIRECTIONS - flame front called FLAME PROPAGATION / limited to TWO valves per cylinder

CMP

Ca, position sensor / provides feedback to ensure cams are rotating as commanded for PCM

valve stem clearance

Clearance between valve stem and valve guide must be within manufacturer's specifications / When too small, valve stem can't be lubricated properly and can gall or stick / When too large, engine suffers from premature wear on valve stem, valve face, and valve seat, and excessive oil passes through guide, resulting in high oil consumption, excessive smoke emitted from exhaust pipe, and possibly fouling of spark plugs

In a(n) ________ engine, there is a camshaft for the intake valves and a separate camshaft for the exhaust valves.

DOHC

DOHC

Dual Overhead Cam Engine / contains 2 camshafts per cylinder head / 1 camshaft typically operates intake valves and other, exhaust valves / usually, camshaft sits on top of valves and operates them directly through bucket lifter w/ no rocker arms or cam followers

pent-roof cylinder heads... --- -valve, ent roof cylinder head --- engines common today / pent-roof cylinder heads have --- - --- design, but typically w/ --- to --- valves / combustion chamber shaped like a fairly --- --- --- / spark plug typically more centrally located in --- --- --- / addition of multiple intake and/or exhaust valves on the cylinder increases the --- at which intake and exhaust gases can be moved --- and --- of the --- ---

MULTI-valve, pent roof cylinder head DOHC engines common today / pent-roof cylinder heads have CROSS-FLOW design, but typically w/ FOUR TO FIVE valves / comb chamb shaped fairly FLAT RECTANGULAR PYRAMID / spark plug typically more centrally located in COMBUSTION CHAMBER TOP / addition of multiple intake and/or exhaust valves on the cylinder increases the SPEED at which intake and exhaust gases can be moved INTO and OUT of the COMBUSTION CHAMBER

Before any machining can begin after the disassembly and cleaning of the cylinder head, the cylinder head should be ________ to locate any external cracks.

Magnafluxed or dye checked

The cylinder head is the part of the engine that is bolted to the --- --- and caps off the top of the --- --- / integral to all ICE --- --- / contains --- --- / controls fuel mix --- / allows --- / forces pistons down --- stroke / contains --- valve / design has a huge influence on the engine's --- and --- ---. It can be made of --- --- or --- --- / most made of --- --- / never designed to withstand --- with --- in the cooling passages

part of the engine that is bolted to the ENGINE BLOCK and caps off the top of the COMBUSTION CHAMBER / integral to all ICE OPERATION EVENTS / contains SPARK PLUG / controls fuel mix ENTRY / allows COMPRESSION / forces pistons down POWER stroke / contains EXHAUST valve / design has a huge influence on the engine's EFFICIENCY and POWER OUTPUT. It can be made of CAST IRON or ALUMINUM / most made of ALUMINUM ALLOY / never designed to withstand FREEZING with WATER in the cooling passages

water jacket

passageway for coolant to flow inside the engine block that is formed when the block is cast

volumetric efficiency

percentage of amount of air actually inducted at given engine speed at full throttle compared to internal engine displacement. For normally aspirated engine (w/out supercharging or turbocharging), engine's volumetric efficiency may peak around 85%. / By adding more than one intake or exhaust valve, volumetric efficiency can be increased while keeping speed of air-fuel mix high, leading to greater power output

bucket-style lifters functions

perform same job as all lifters: transmit movement from cam lobe to valve tip / may be hydraulic or mechanical / To adjust valve clearance in the mechanical lifter, you must change the wafer installed on top of the bucket /

camshaft follower

performs the same basic function as a rocker arm: It opens a valve / has a pivot on one end and a slider or roller near the center that directly contacts the camshaft lobe

During the magnafluxing process, after applying the powder, a(n) ______ creates a magnetic field that causes a high concentration of magnetic flux at the surface cracks, which attract the iron powder when applied.

permanent magnet / electromagnet

electronic module valve timing through use of phasers

phasers adjust position of one or both camshafts hydraulically while engine is operating

valve face

portion of that actually seals off port / commonly ground to about 45 degree angle to provide positive seal during combustion process / may be coated in a material called Stellite™ /

valve margin

portion of valve between face and head / gets thinner as valve face is machined during valve job / if too thin, burns in short time / measure margin and compare to specification before use

valve tip

portion of valve stem coming in direct contact with rocker arm, cam follower, or bucket lifter, which opens valve

O-rings function

preferred in high-performance engines / used to seal components / sometimes used instead of gaskets / can be used to seal stationary and slowly rotating or sliding shafts and seals surfaces / generally effective at sealing high pressures where differential speed between opposing surfaces is minimal / has no mechanism for self-adjustment / Once worn, sealing ability is compromised

Atmospheric pressure is the pressure of --- surrounding everything caused by --- and the --- of air. The higher from sea level, the --- the atmospheric pressure / average atmospheric pressure at sea level is 14.7 pounds per square inch (psi), or 101 kilopascals (kPa)

pressure of AIR surrounding everything caused by GRAVITY and the WEIGHT of air. The higher from sea level, the LOWER the atmospheric pressure / average atmospheric pressure at sea level is 14.7 pounds per square inch (psi), or 101 kilopascals (kPa