AERA Component Inspection & Quality Control 4 — Questions and Answers
Question 1: A cylinder head surface that shows low spots when checked with a straight edge and feeler gauge requires:
- Application of gasket sealant to compensate
- Resurfacing to restore flatness (Correct answer)
- Installation of a thicker head gasket
- Torquing the head bolts tighter
Correct answer: Resurfacing to restore flatness
Low spots indicate warpage; resurfacing (milling or grinding the deck) removes material to restore a flat sealing surface within specification.
Question 2: The maximum allowable warpage for a typical V8 engine cylinder head deck surface is often specified as:
- 0.010 in (0.25 mm) overall
- 0.004 in (0.10 mm) overall or 0.002 in per 6 in (Correct answer)
- 0.015 in (0.38 mm) per foot
- 0.001 in (0.025 mm) overall
Correct answer: 0.004 in (0.10 mm) overall or 0.002 in per 6 in
Most OEM specifications limit warpage to approximately 0.004 in overall or 0.002 in per any 6-inch span to ensure proper head gasket sealing.
Question 3: When inspecting valve seats, a seat that is too wide will cause:
- Excessive valve-to-seat leakage
- Poor heat transfer from the valve face and valve burning (Correct answer)
- Valve recession into the head
- Increased spring pressure requirements
Correct answer: Poor heat transfer from the valve face and valve burning
Overly wide seats reduce the contact pressure per unit area, impeding heat transfer from the valve to the head, which can cause the valve to overheat and burn.
Question 4: What does excessive end play in a crankshaft indicate?
- Worn main bearing journals
- Worn or damaged thrust bearings/washers (Correct answer)
- Incorrect main bearing oil clearance
- Bent crankshaft
Correct answer: Worn or damaged thrust bearings/washers
Crankshaft end play is controlled by thrust bearings or thrust flanges; worn thrust surfaces allow excessive axial movement of the crankshaft.
Question 5: A technician finds that a block's main bearing tunnel measures 0.003 in larger in diameter than specification. The BEST corrective action is:
- Use oversize bearings to compensate
- Line bore or line hone the block to restore proper geometry, then use correct bearings (Correct answer)
- Use bearing shims to reduce the bore size
- Apply bearing retainer compound and reuse the bore
Correct answer: Line bore or line hone the block to restore proper geometry, then use correct bearings
An oversized main tunnel must be line bored or line honed back to the correct diameter and roundness before installing bearings of the proper size.
Question 6: Which surface finish characteristic is most critical for proper piston ring seating in a honed cylinder bore?
- Roughness average (Ra) and crosshatch angle (Correct answer)
- Mirror polish with zero surface texture
- Horizontal parallel grooves
- Random directional scratches from wet sanding
Correct answer: Roughness average (Ra) and crosshatch angle
The correct Ra (surface roughness) and a crosshatch angle of 45–60° provide the proper oil retention and ring seating characteristics for new rings.
Question 7: When performing a wet compression test and results improve significantly compared to a dry test, this indicates:
- A leaking head gasket
- Worn or damaged piston rings (Correct answer)
- A stuck-open exhaust valve
- Excessive valve stem clearance
Correct answer: Worn or damaged piston rings
Oil added to the cylinder temporarily seals worn rings; a big improvement from dry to wet test confirms ring and/or bore wear as the source of low compression.
AERA Component Inspection & Quality Control 4
A cylinder head surface that shows low spots when checked with a straight edge and feeler gauge requires: