FAA Powerplant Written Practice Test

Which component is affected if there is a blow-by in the intake valve?

1. Carburetor

2. Piston rings

3. Exhaust valves

4. Fuel injectors

The correct answer is: Piston rings

When there is blow-by in the intake valve, it primarily affects the piston rings. Blow-by refers to the phenomenon where combustion gases escape past the piston rings into the crankcase or back through the intake system. If the intake valve is not sealing properly, it can create situations that promote this occurrence. Piston rings are designed to maintain seal integrity in the combustion chamber. They help contain the high-pressure gases generated during combustion and prevent them from escaping past the piston. If there is a problem with the intake valve, it might lead to abnormal pressure conditions that could cause or exacerbate wear on the piston rings, potentially leading to reduced sealing capability and increased oil consumption. In contrast, components such as the carburetor, exhaust valves, and fuel injectors do not directly respond to blow-by associated with intake valves in the same manner. These components have their specific functions and are affected by different issues related to fuel delivery, air-fuel mixture, and exhaust flow rather than the sealing performance of the intake valve and its interaction with the piston.