Question 1

Technician A says that installing a compression ring upside down can cause oil consumption. Technician B says that the top compression ring groove usually suffers more wear than the other ring grooves. Who is right?

Accepted Answer

Technician A is correct that installing a compression ring upside down can cause oil consumption because the ring won't seal properly. Technician B is also correct that the top compression ring groove usually suffers more wear than the other ring grooves, as it has the most load and is exposed to the hottest combustion gases. Therefore, both technicians are correct.

Question 2

What is the name of the piston pin retaining method where the piston pin has a bushing in the connecting rod and lock rings at the ends of the piston bore?

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Question 3

Where is the largest diameter of the piston found?

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Question 4

Piston balance is more important with in-line engines than with V-type engines.

Accepted Answer

In-line engines generally have better natural balance compared to V-type engines, making piston balance less of a concern for in-line engines.

Question 5

What tool is used to check piston ring end gap clearance?

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Question 6

Which type of cylinder arrangement sometimes uses offset connecting rods?

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Question 7

Why is the piston pin bore offset from the piston centerline?

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Question 8

What is the name of a piston that has a full skirt all the way around its bottom?

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Question 9

Which of the following statements is/are true when installing full-floating piston pin lock rings?

Accepted Answer

Full-floating piston pin lock rings do not have a specific orientation for the opening or the rounded side in relation to the direction of installation. The critical aspect is ensuring they are properly seated in the groove of the piston or rod. The statements about orientation do not apply universally and can vary based on specific engine designs or manufacturer recommendations.

Question 10

Technician A says that cast pistons run cooler than forged pistons. Technician B says that cast pistons are stronger than forged pistons. Who is right?

Accepted Answer

Cast pistons are made of a softer metal than forged pistons, which allows them to conform to the cylinder walls more easily. This reduces friction and heat, making cast pistons run cooler than forged pistons. However, cast pistons are not as strong as forged pistons, which are made of a harder metal that is less likely to break under stress.

Question 11

What is the name of the style of piston skirt that is cut away on the sides to allow clearance for the crankshaft counterweights?

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Question 12

Why is there a hole or slot in the oil ring groove?

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Question 13

How much can the cylinder bore be out of round when using moly or chrome piston rings?

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Question 14

Which ring groove wears the most?

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Question 15

How is a top ring groove checked for excessive wear?

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Question 16

Which is larger: the diameter of the head or crown of the piston or the diameter of the skirt?

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Question 17

Does a 0.030" oversized piston weigh the same as the original standard piston?

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Question 18

Technician A says that some piston rings have chamfers or reliefs cut into them to cause them to twist. Technician B says that chrome rings should not be used in out-of-round cylinders. Who is right?

Accepted Answer

Technician A is correct that some piston rings have chamfers or reliefs cut into them to cause them to twist. This twist helps the ring seat better against the cylinder wall, creating a better seal. 
Technician B is correct that chrome rings should not be used in out-of-round cylinders. Chrome rings require a perfectly round cylinder to function properly. If the cylinder is out-of-round, the chrome ring will not conform properly and will not create an effective seal.

Question 19

What is the most common method of retaining the piston pin?

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Question 20

Technician A says that the full skirt piston used on long stroke engines is called a "slipper" skirt. Technician B says that a piston skirt that is cut away on its sides to clear the crankshaft counterweights is called a "trunk" skirt. Who is right?

Accepted Answer

Technician A is incorrect because a "slipper" skirt piston is actually a type of piston with sides cut away to reduce weight, not a full skirt piston used on long stroke engines. Technician B is also incorrect because a piston skirt cut away on its sides to clear the crankshaft counterweights is known as a "slipper" skirt, not a "trunk" skirt. A "trunk" skirt refers to a more traditional, full-coverage piston skirt.

Quiz 12: Pistons, Rings, and Connecting Rods