AG Mechanics CDE Practice Exam

What is the most common angle on a valve face?

1. 30 degrees

2. 31 degrees

3. 45 degrees

4. 46 degrees

The correct answer is: 30 degrees

Valve faces are typically cut at an angle to create a sealing surface between the valve and valve seat. The most commonly used angle is 30 degrees because it provides a good balance between flow and durability. Options B, C, and D are incorrect because they are not as commonly used as 30 degrees. Option B of 31 degrees is only slightly different and does not offer significant advantages. Option C of 45 degrees is used for high-performance engines, but it can lead to overheating and valve failure in regular use. Option D of 46 degrees is used for drag racing engines, but it can cause loss of power and increased wear in regular use. Therefore, 30 degrees is the most common and practical angle used for valve faces.