Question 1

Technician A says that after refinishing a 45⁰ valve seat, a 30⁰ angle should be used to position the valve seat on the valve face. Technician B says that before a valve guide is repaired, the valve seat should always be ground. Who is right?

Accepted Answer

Technician A is correct that a 30⁰ angle should be used to position the valve seat on the valve face after refinishing. Technician B's statement about valve seat grinding before repairing a valve guide is not always necessary and therefore incorrect.

Question 2

Technician A says that most exhaust valves are smaller than intake valves because exhaust gases are under high pressure. Technician B says that intake valves are larger than exhaust valves. Who is right?

Accepted Answer

Exhaust valves are typically smaller because exhaust gases are expelled under pressure, while intake valves are larger to allow more air-fuel mixture into the cylinder for better combustion.

Question 3

Technician A says that the face of the valve should overhang slightly into the combustion chamber when the valve is closed. Technician B says that the throat angle would most likely result in a ruined valve seat if ground too much. Who is right?

Accepted Answer

Both technicians are correct. Technician A is correct in stating that the valve face should slightly overhang into the combustion chamber for optimal sealing and performance. Technician B is correct in cautioning that over-grinding the throat angle can damage the valve seat, affecting the valve's ability to seal properly.

Question 4

Technician A says that narrow valve seats exert a higher force on the seat area. Technician B says that if intake and exhaust valve springs are of equal pressure, then the larger valve must have a narrower seat in order to have the same seating pressure as the smaller valve. Who is right?

Accepted Answer

Technician A is correct because a narrow valve seat concentrates the force over a smaller area, resulting in higher pressure at the contact point between the valve and the seat. Technician B is also correct because, for valves of different sizes to have the same seating pressure with equal spring pressures, the larger valve must have a narrower seat to compensate for its larger surface area, ensuring the force is distributed in a way that maintains equal pressure.

Question 5

Technician A says that the sodium filling used in some exhaust valve stems lightens the valve for better low-speed operation. Technician B says that a valve that has a wide margin must be replaced. Who is right?

Accepted Answer

Technician A is incorrect because sodium-filled valves are used to improve cooling, not to lighten the valve. Technician B is incorrect because a wide valve margin does not necessarily mean the valve must be replaced; it depends on the valve's condition and specifications.

Quiz 8: Cylinder Head: Springs, Valves, and Valve Sets

Technician A says that after refinishing a 450 valve seat, a 300 angle should be used to position the valve seat on the valve face. Technician B says that before a valve guide is repaired, the valve seat should always be ground. Who is right?

Technician A says that most exhaust valves are smaller than intake valves because exhaust gases are under high pressure. Technician B says that intake valves are larger than exhaust valves. Who is right?

Technician A says that the face of the valve should overhang slightly into the combustion chamber when the valve is closed. Technician B says that the throat angle would most likely result in a ruined valve seat if ground too much. Who is right?

Technician A says that narrow valve seats exert a higher force on the seat area. Technician B says that if intake and exhaust valve springs are of equal pressure, then the larger valve must have a narrower seat in order to have the same seating pressure as the smaller valve. Who is right?

Technician A says that the sodium filling used in some exhaust valve stems lightens the valve for better low-speed operation. Technician B says that a valve that has a wide margin must be replaced. Who is right?

Technician A says that after refinishing a 45⁰ valve seat, a 30⁰ angle should be used to position the valve seat on the valve face. Technician B says that before a valve guide is repaired, the valve seat should always be ground. Who is right?