engine final exam study guide
The camshaft makes ________________ for every revolution of the crankshaft
1/2 revelution
A DOHC V-6 engine has how many camshafts?
4
the most common valve face angle is
45
Power balance testing is being discussed. Technician A says that during testing, a large drop in rpm indicates a cylinder that is not producing necessary power. Technician B says that on some vehicles, this test can be performed with a scan tool because of factory programing. Who is correct?
B only
Interference parts are different size components that are precision fit so that a puller or press is necessary to remove or install.
TRUE
Tech A says that the crankshaft determines the stroke of an engine. Tech B says the connecting rod determines the stroke of an engine. Who is correct?
Tech A only
Tech A says that valve stem height is measured from the valve spring seat to the valve stem tip. Tech B saysthe incorrect valve stem height can cause excessive oil consumption. Who is correct?
Tech A only
Tech A says exhaust valve lash is generally set wider than intake valve lash due to valve overlap. Tech B says exhaust valve lash is set wider due to added heat from the exhaust. Who is correct?
Tech B only
what can engines be made of? types of metals
iron base alloys such as structural steels, stainless steels, iron base sintered metals, and cast iron and aluminum alloy parts for the piston.
A rotating force is called ________.
torque
A cylinder that has a dramatic increase during a wet compression test most likely has problems with piston rings. true or false
true
Connecting rod bearings receive oil after it passes through the crankshaft through small passages that are fed through the main bearings.
true
Full-floating piston pins are held in by locks or snap rings that usually allow the pin to be removed without a press.
true
Head gaskets can leak combustion into the cooling system when they fail. true or false.
true
Spark plugs can help identify problems with fuel, ignition, or mechanical issues. true or false
true
The margin of the valve must be within specification to properly dissipate heat. true or false:
true
umbrella valve stem moves up and down with the valve true or false:
true
A SOHC. V-8 engine has how many camshafts?
two
An automotive internal combustion engine
uses energy released when compressed air fuel mixture is ignited
Which of the following is not used in the calculation of engine displacement?
valve arrangement
compression testing?
?
cylinder leakage test?
?
how do you do a crankshaft installation
?
what would cause the crankshaft to begin binding?
?
A car has come into a shop with an engine misfire. A power balance test has been performed with the following results .Cylinders 1 2 3 4 RPM Drop 10 150 145 155 Technician A says that cylinder 1 may have low compression. Technician B says that cylinders 2-3-4 are not working properly. Who is correct?
A only
Technician A says that it may be possible to file piston rings that have the end gaps too tight. Technician B says that a ring compressor is used to aid in installing the piston rings onto the pistons. Who is correct?
A only
what is the difference between out of round and runout
Circular runout controls only a particular circular cross section of a part, while total runout controls the entire surface of the part.
why is having proper valve lash is important?
Excessive lash will cause noise in the engine and wear in the valvetrain, while lashing the valve too tightly will cause the valve to hang open and the cylinder won't run.
Most cylinder wear occurs in the middle of the cylinder.
FALSE
All piston pins are positioned exactly in the center of the piston skirts.
False
The harmonic balancer attaches to the rear of the crankshaft and is used to reduce vibrations.
False
When a main bearing is installed, the ends of the bearing should not protrude past the parting line of the saddle and cap of the block.
False
All overhead valve engines ________.
Have the valves located in the cylinder head
Cylinder taper is being discussed. Technician A says taper does not affect the ring gap as the piston goes up and down. Technician B says that up to.010" (.254mm) is usually an acceptable amount of taper. Who is correct?
Neither A nor B
Technician A says that when a long block is purchased, the old cylinder heads must be reused. Technician B says that a long block includes the cylinder heads, intake and exhaust manifolds. Who is correct?
Neither A nor B
Crankshaft journals are measured for all of the following EXCEPT ____.
RUN OUT
Technician A says that engine block cylinders are measured for taper. Technician B says that the piston rings typically cause the most wear in the middle of the cylinder. Who is correct?
TECH A ONLY
A bedplate has all of the main caps cast as one unit.
TRUE
During operation of an engine, the crankshaft rides on a thin layer of oil.
TRUE
Tech A says that positive valve stem seals must be installed before the valves are installed. Tech B says positive valve stem seals must be firmly pushed down over the valve guide. Who is
Tech B only
Tech A says worn valve stem seals may cause rapid valve guide wear. Tech B says worn valve stem seals may cause excessive oil consumption. Who is correct?
Tech B only
Tech. A says that preignition is harmless. Tech B says that detonation can cause severe engine damage. Who is correct?
Tech B only
Technician A says crankshafts in high performance engines are generally cast iron. Technician B says crankshafts in high performance engines may be forged iron. Who is correct?
Technician B
what are water pump growling noises?
either a drive belt is loose, or the water pump pulley is bad.
Most of a valves heat is dissipated through the
face
Black smoke from the exhaust pipe is usually caused by coolant mixing in the combustion chamber. true or false
false
Higher compression ratios can be attained from dished pistons instead of domed.
false
if a timing belt brakes on an interference engine the engine valves will not bend or break. true or false
false
true or false: A compression gauge is designed to tell the technician what the compression ratio of an engine is.
false
Which of the following is a typical cylinder head tightening sequence?
from center to outside
each of the following is a likely cause of detonation EXCEPT
fuel with too high of a octane rating
all overhead valve engines
have the valves located in the cylinder head
Hydraulic valve lifters can make a ticking noise when the engine is running. Incorrect answer:
if the valve lash is too loose
Which type of valve guide is most used in a cast iron cylinder head?
integral
exhaust stroke purpose?
movement is at: BDC-TDC - to ready the cylinder for the intake as well as to remove any unburned or spent gasses valve position: intake closed; exhaust open
the throttle is wide open. what happens to the oil pressure?
oil pressure would go up.
The intake valve opens at 39 degrees BTDC and closes at 71 degrees ABDC. the exhaust valve opens at 78 degrees BBDC and closes at 47 degrees ATDC. which answer is correct?
overlap is 86*
in a normally operating engine intake and exhaust valves are opened by the camshaft and closed by?
positive lip type
Fractured rod caps are used with which type of rod construction?
powdered metal
In a 4 stroke cycle engine, The piston is driven down in the cylinder by expanding gasses during the __________ stroke.
power
The proper tool or tools used to measure gasket surface warpage is?
straight edge and feeler gauge
Tech A says the camshaft gear is twice the diameter of the crankshaft gear. Tech B says the crankshaft gear is twice the diameter of the camshaft gear. Who is correct?
tech A only
Technician A says most engines use two oil control rings and one compression ring. Technician B says low-tension oil rings reduce friction and improve fuel economy. Who is correct?
tech B
Tech A says mechanical valve lash automatically compensates for wear and temperature changes. Tech B says hydraulic valve lash once adjusted automatically adjusts for wear and temperature changes. Who is correct?
tech B only
Tech A says valve lift is how long the valve stays open. Tech B says valve duration is how long the valve stays open. Who is correct?
tech B only
Tech a says valve lash must be adjusted on the toe of the cam lobe. Tech B says valve lash must be adjusted on the heel of the cam lobe. Who is correct?
tech B only
Technician A says that a crankshaft determines the stroke of an engine. Technician B says the length of the connecting rod determines the stroke of an engine. Which technician is correct?
technician A
Hydraulic lifters may not bleed down properly and cause an engine to miss if.
the wrong SAE oil is used
how to check for a stretched chain?
this is deflection and we usually measure it with a ruler
in a normally operating engine intake and exhaust valves are opened by the camshaft and closed by?
valve spring
Which of the following would most likely cause a low running compression reading on one cylinder?
worm cam lobe
how to check for warpage?
you check with a straightedge and a feeler gauge
engine timing, and how does it affect performance?
you could experience several problems with your engine with improper ignition timing like knocking, hard to start, increase fuel usage, overheating, and reduced power.
the crankshaft rotates how many degrees to complete the 4 stroke cycle?
720*
valve lift
- Total amount of lift present at the valve itself. - May vary from cam lift due to rocker arm ratios, clearances, etc.
engine parts
- cylinder head - exhaust valve - rings - cylinder bore - connecting rod - crankshaft - piston - intake valve
compression stroke purpose?
- the movement is BDC-TDC - compresses the air/ fuel mixture valve position: intake closed; exhaust open
intakes stroke purpose?
- the movement is TDC-BDC - it's purpose its that it brings the fuel/air into the combustion chamber. Valve position: intake is open; exhaust is closed
what are the crankshaft measurements?
- you measure a crankshaft micrometer
power stroke purpose?
-piston movement: TDC-BDC -rapidly builds the cylinder pre valve position: intake closed; exhaust open *the only stroke that makes power*
oil pressure- oil pressure light
-pressure is going to be higher when cold -pressure is going to be lower when warm
Cylinder heads with 4 valves flow more air than those with 2 valves because they:
1) have a greater open area 2) increase the velocity of air
what are the four strokes of the engine?
1) intake 2) compression 3) power 4) exhaust
Of the three main types of piston materials, forged pistons are the strongest.
True
Adjusting valve lash using EOIC: method works with any pushrod engine using solid lifters
1) screw the poly-locks of the rocker arms until they just finger tight. 2)Then, rotate the engine until the exhaust pushrod on the cylinder you are working on begins to move upward. 3) You'll be looking for any rocker arm movement. This is the process of exhaust opening. 4) At this point, you can adjust the intake because the intake valve will be closed, ensuring that the intake lifter is on the base circle of the cam. 5) This is particularly important as you run the risk of hanging open a valve if lash is adjusted when the lifter is not in this position. 6) Place a feeler gauge between the valve tip and the rocker arm. 7)Tighten the poly-lock of the rocker arm until the proper lash is found. 8) When you get to your preferred lash, hold the adjuster nut in place and set it with the inner screw using an Allen wrench. 9)The poly-lock adjuster nut adjusts the amount of valve lash while the set screw locks it into place. 10) Finally, tighten with an adjustable torque wrench until it clicks at 20 foot-pounds of torque. This tightens the adjuster nut to the inner set screw and ensures that they do not come apart.
what are hydraulic lifters?
1) uses oil to compensate for the effects of engine temperature and valvetrain wear. 3) Usually maintains zero lash 2) Oil supplied but the oil pump is pushed through the oil feed holes of the lifter bore into the lifter body. 4) Adjust automatically, they can overcompensate at higher speed engines
Adjusting valve lash: using regular method
1)When the exhaust valve just begins to open on the first cylinder in the firing order, 2) adjust the intake valve by loosening the adjusting nut slightly while spinning the pushrod until you feel lash in the rocker's arm. 3)Tighten the adjusting nut until the slack is taken out of the rocker arm and pushrod
Atmospheric pressure at sea level is ?
14.7
a 4 stroke cycle engine stroke is how many degrees of crankshaft rotation
180*
Compression test results are being discussed. Technician A says that if one cylinder is found to be low, a wet test should be performed to help narrow down the diagnoses. Technician B says that a difference of 10% between cylinders would be acceptable.
Both A and B
Technician A says that a blown head gasket can cause coolant to mix with the engine oil to create a coffee-colored milkshake-like substance. Technician B says that white smoke from the exhaust pipe can be the result of a blown head gasket. Who is correct?
Both A and B
Technician A says that an even firing V8 engine has a power stroke start every 90 degrees of crankshaft rotation. Technician B says that a four-cylinder engine will start a power stroke every 180 degrees of rotation. Who is correct?
Both A and B
A crankshaft has just been installed into the engine block, and all of the caps have been torqued into place. The crankshaft would not rotate by hand at this time. Technician A says this is normal; rotating a newly installed crankshaft will usually take the force of a wrench turning the crankshaft by the front bolt. Technician B says that this could be caused by mixing up the placement of two main caps. Who is correct?
b only
A cylinder leakage test is being performed. What is the most likely cause when air is blowing out through the radiator?
blown head gasket
A cylinder is reading a 100 percent leakage during a cylinder leakage test. Technician A says the exhaust valve could be open. Technician B says the exhaust valve could be bent. Who is correct?
both A and B
Compression testing is being discussed. Technician A says that the ignition should be disabled. Technician B says that the fuel system should be disabled. Who is correct?
both A and B
Two techs are discussing VVT. Tech A says that changing the exhaust valve timing helps with exhaust emissions. Tech B says that changing the intake valve timing helps increase low speed torque. Who is correct?
both A and B
Tech A says valve springs should be checked for squareness and pressure. Tech B says that seat pressure is compressing the spring to the same height when the valve is closed. Who is correct?
both tech A and B
Tech A says valves are opened by the camshaft Tech B says valves are closed by the valve spring Who is correct
both techs A and B
valve stem seals:
control oil flow to the valve stem
Which test will most accurately pinpoint the finding of a failed intake valve?
cylinder leakage test
An engine is idling rough and has a lack of power. Which test should be performed first?
cylinder power balance test
what occurs when another flame starts after the spark
detonation
