ASE Engine Repair A1 3 — Questions and Answers
Question 1: During an engine rebuild, a technician measures the piston ring end gap and finds it is smaller than the manufacturer's minimum specification. What is the correct action?
- File the ring ends to increase the gap to spec (Correct answer)
- Install the ring as-is since tighter is better for compression
- Replace the rings with a smaller bore size
- Hone the cylinder to reduce its diameter
Correct answer: File the ring ends to increase the gap to spec
Piston ring end gap must be within specification. If the gap is too small, heat expansion during operation can cause the ring ends to butt together, collapsing the ring and damaging the cylinder wall. The correct fix is to file the ring ends carefully until the gap meets the minimum specification.
Question 2: A technician is checking main bearing clearance using Plastigage. After removing the cap, the Plastigage strip is wider than the comparison scale indicates. What does this mean?
- The bearing clearance is less than specification
- The bearing clearance is greater than specification (Correct answer)
- The crankshaft journal is within tolerance
- The Plastigage was installed incorrectly
Correct answer: The bearing clearance is greater than specification
Plastigage works by being compressed between the journal and bearing. After assembly and disassembly, its width is compared to the scale. A wider crushed strip means less compression occurred, which indicates the bearing clearance is greater (looser) than specification. Excess clearance leads to low oil pressure and bearing noise.
Question 3: What is the purpose of a valley gasket (valley pan gasket) in a V-type engine?
- It seals the intake manifold to the cylinder heads
- It seals the lifter valley area to prevent oil leaks into the intake system (Correct answer)
- It seals the timing cover to the block
- It seals the oil pan to the block
Correct answer: It seals the lifter valley area to prevent oil leaks into the intake system
In many V-type engines, the valley between the cylinder banks can be exposed to oil splashing from the lifters and camshaft. The valley pan gasket seals this area to prevent oil from leaking into the intake manifold or combustion chambers, which would cause blue smoke and oil consumption.
Question 4: A technician notices a deep groove worn into a camshaft lobe on one cylinder. Which component is most likely the primary cause of this failure?
- Worn timing chain
- Failed hydraulic lifter not rotating on the lobe (Correct answer)
- Incorrect valve spring pressure
- Stretched rocker arm studs
Correct answer: Failed hydraulic lifter not rotating on the lobe
Hydraulic lifters (and solid lifters) are designed to rotate slightly as they follow the cam lobe. This rotation distributes wear evenly. If a lifter seizes and stops rotating, it will wear a groove into the lobe in the same spot on every revolution. Lobe failure is almost always associated with a stuck or collapsed lifter.
Question 5: Which method is used to check for a warped cylinder head on a removed head?
- Measure with a dial bore gauge across the combustion chambers
- Place a straightedge and feeler gauge across multiple directions on the deck surface (Correct answer)
- Pressure test the head with compressed air and water
- Check the head with a magnetic crack detector only
Correct answer: Place a straightedge and feeler gauge across multiple directions on the deck surface
A straightedge and feeler gauge is the standard method to check cylinder head flatness. The straightedge is placed lengthwise, crosswise, and diagonally across the head deck surface. A feeler gauge is used to measure any gap between the straightedge and the deck. Warpage beyond the manufacturer's limit requires resurfacing.
Question 6: What does the term "deck height" refer to in engine rebuilding?
- The height of the valve stems above the cylinder head
- The distance from the top of the piston to the block deck surface at TDC (Correct answer)
- The depth of the combustion chamber in the cylinder head
- The clearance between the piston skirt and cylinder wall
Correct answer: The distance from the top of the piston to the block deck surface at TDC
Deck height (or piston-to-deck clearance) is the measurement from the top of the piston crown to the top surface of the engine block when the piston is at TDC. This measurement is critical for calculating compression ratio and ensuring correct head gasket thickness selection during an engine rebuild.
ASE Engine Repair A1 3
During an engine rebuild, a technician measures the piston ring end gap and finds it is smaller than the manufacturer's minimum specification.
What is the correct action?