AERA Cylinder Head Rebuilding & Valve Train 3

Question 1

What is the purpose of measuring valve stem runout (stem straightness) before reusing a valve?

Accepted Answer

A bent stem causes guide wear, side loading on the seat, and erratic valve sealing

Answer

A bent valve stem causes the valve to wobble in the guide, accelerating guide wear, creating an off-center seat contact, and producing inconsistent sealing.

Question 2

On a hydraulic roller lifter engine, what is the specified preload range typically applied to the lifter after zero lash is established?

Accepted Answer

1/4 to 3/4 turn past zero lash

Answer

Hydraulic lifters require 1/4 to 3/4 turn past zero lash to keep the plunger in its operating range; too little causes noise and too much holds valves open.

Question 3

Which type of valve spring design is most resistant to harmonic surge at high engine speeds?

Accepted Answer

Variable-pitch (beehive or dual) spring

Answer

Variable-pitch and beehive springs have progressively changing coil spacing, which shifts the resonant frequency away from the engine's operating RPM range and suppresses harmonic surge.

Question 4

What condition does a valve spring tester measure, and at what point is a spring considered unserviceable?

Accepted Answer

It measures spring pressure at a specified compressed height; a spring is unserviceable if pressure is more than 10% below spec

Answer

Spring testers compress the spring to the installed height and measure the load; a reading more than 10% below spec means the spring has weakened enough to allow float at high RPM.

Question 5

When installing valve keepers (locks) in a cylinder head, what tool-related practice prevents them from unseating during assembly?

Accepted Answer

Apply a small amount of assembly grease to the keeper grooves to hold them in place while the spring compressor is released

Answer

Assembly grease holds the keepers in the groove while the spring compressor is slowly released, preventing them from popping out and becoming a safety hazard or damaging the engine.

(AERA) Automotive Engine Rebuilders Association Certification Practice Test

(AERA) Automotive Engine Rebuilders Association Certification Practice Test

AERA Cylinder Head Rebuilding & Valve Train 3