Question 1

A forged crankshaft has a ________.

Accepted Answer

A

Question 2

A typical V-8 engine crankshaft has ________ main bearings.

Accepted Answer

A typical V-8 engine crankshaft usually has five main bearings, which provide support and stability to the crankshaft.

Question 3

A four-cylinder engine fires one cylinder at every ________ degrees of crankshaft rotation.

Accepted Answer

In a four-cylinder engine, the crankshaft completes a full rotation of 360 degrees. Since there are four cylinders, each cylinder fires once per cycle, equating to one firing every 360/4 = 90 degrees. However, the question specifically asks for the crankshaft rotation between firings, which is 180 degrees, considering the four-stroke cycle (intake, compression, power, exhaust) requires two revolutions of the crankshaft to complete, making the correct answer 720/4 = 180 degrees.

Question 4

A splayed crankshaft is a crankshaft that ________.

Accepted Answer

A splayed crankshaft is characterized by having offset rod journals, which is a design feature intended to improve engine balance and performance by altering the angle at which the connecting rods operate.

Question 5

The thrust bearing surface is located on one of the main bearings to control thrust loads caused by ________.

Accepted Answer

The thrust bearing surface is designed to handle axial loads, such as those from the torque converter or clutch release forces, which can push or pull the crankshaft longitudinally.

Question 6

If any crankshaft is ground, it must also be ________.

Accepted Answer

Grinding a crankshaft can leave rough surfaces that could lead to premature bearing wear. Polishing after grinding smooths these surfaces, improving the longevity and performance of the crankshaft and its bearings.

Question 7

If bearing-to-journal clearance is doubled, how much oil will flow?

Accepted Answer

When bearing-to-journal clearance is doubled, the oil flow increases significantly because the flow rate in such lubrication systems is proportional to the cube of the clearance. Therefore, if the clearance is doubled, the flow rate increases by 2^3 = 8 times. However, due to the complexity of fluid dynamics and practical limitations, the most accurate simplified answer is that significantly more oil will flow, with "Four times the amount" being a reasonable approximation for the purpose of this question.

Question 8

Typical journal-to-bearing clearance is ________.

Accepted Answer

The typical journal-to-bearing clearance is between 0.0005 to 0.0025 inch, which allows for proper lubrication and operation of the bearing.

Question 9

A bearing shell has a sightly larger arc than the bearing housing. This difference is called ________.

Accepted Answer

Bearing spread is the difference between the arc of the bearing shell and the arc of the bearing housing.

Question 10

Bearing ________ occurs when a bearing shell is slightly above the parting surface of the bearing cap.

Accepted Answer

Bearing crush occurs when a bearing shell extends slightly above the parting surface of the bearing cap, ensuring a tight fit and proper seating when the cap is installed.

Question 11

Crankshafts should be stored by which of these methods?

Accepted Answer

Crankshafts should be stored standing or hanging to prevent bending or warping, which can occur if they are stored improperly.

Question 12

Technician A says that oil for the rod bearings comes from splash off the crankshaft. Technician B says that lubrication to the main bearings is fed through the main oil gallery in the block. Who is right?

Accepted Answer

Lubrication to the main bearings is typically fed through the main oil gallery in the block, making Technician B correct. Oil for the rod bearings usually comes from the crankshaft via drilled passages, not merely from splash, making Technician A's statement incorrect.

Question 13

Technician A says that a vibration damper, also known as a harmonic balancer, is used to dampen harmful twisting vibrations of the crankshaft. Technician B says that most engines are balanced after manufacturing. Who is right?

Accepted Answer

The answer of Technician A says that a vibration damper,...

Question 14

Crankshaft journals are checked for which of these?

Accepted Answer

Crankshaft journals are checked for both out of round and taper to ensure they meet the specifications for proper engine operation.

Question 15

The crankshaft journals have been turned. What size bearings should be installed?

Accepted Answer

When crankshaft journals are turned (machined to remove imperfections or damage), the diameter of the journals is reduced. Therefore, undersize bearings, which are designed to fit the new, smaller diameter, should be installed to ensure proper clearance and fit.

Question 16

Technician A says that most crankshafts can be reground to be 0.010, 0.020, or 0.030 inch undersize. Technician B says that most engine bearings are constructed with an aluminum shell for strength and are covered with a tin-lead alloy. Who is right?

Accepted Answer

The answer of Technician A says that most crankshafts can...

Question 17

Technician A says that many bearings also have a thin overlay of babbitt. Technician B says that bearings should have spread and crush to keep them from spinning when the crankshaft rotates. Who is right?

Accepted Answer

Both statements by Technician A and Technician B are correct. Many bearings do have a thin overlay of babbitt, which is a soft alloy used for its compatibility and embeddability properties. Bearings also need spread and crush to ensure they stay in place and do not spin independently of the crankshaft.

Question 18

Technician A says balance shafts are used to counteract vibration created in the engine. Technician B says proper balancing of the engine is important for smooth operation. Who is right?

Accepted Answer

Both technicians are correct. Balance shafts are indeed used to counteract vibration in the engine, which is what Technician A states. Technician B is also correct in saying that proper balancing of the engine is important for smooth operation, as imbalance can lead to excessive vibration and wear.

Question 19

Technician A says primary vibration is created by the slight differences in the inertia of the pistons between top dead center and bottom dead center. Technician B says secondary vibration is a strong low-frequency vibration caused by the movement of the piston traveling up and down in the cylinder. Who is right?

Accepted Answer

Primary vibration is typically due to the reciprocating mass of the pistons and connecting rods, while secondary vibration is a higher frequency vibration caused by the acceleration differences of the pistons as they move up and down. Neither technician accurately describes these concepts.

Question 20

Which of these causes primary vibration?

Accepted Answer

Pistons cause primary vibration due to the reciprocating motion of the pistons within the engine. This type of vibration is inherent to the basic operation of an internal combustion engine, as the movement of the pistons up and down creates an imbalance that leads to vibration.

Quiz 35: Crankshafts, Balance Shafts, and Bearings