Five free practice questions on cylinder head and valve train: content area B of the ASE A1 Engine Repair test, 6 of its 45 scored questions (13.3%). They are in the ASE format: four options, one best answer. Answer each one before opening the explanation. No account, no email.
01The questions
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After a valve spring on a rebuilt head is compressed and released, one of the two valve locks (keepers) on that valve sits noticeably higher in the retainer than the other. What does this show?
- The spring's installed height is too tall
- The high lock is not in the stem groove
- The valve has sunk too deep into its seat
- The stem has worn where it rides in the guide
Show the answer
B. Correct. The two locks fit the groove in the stem and are wedged into the retainer's taper, so they sit level when both are seated. A lock riding high is caught outside the groove and can let the retainer go, dropping the valve, so the spring is compressed again and the lock seated.
Why not the others
A. An installed height that is too tall raises the retainer and both locks together, so they would still sit level with each other. One lock higher than the other means that lock is not in the stem groove.
C. A valve sunk into its seat raises its stem tip and changes installed height, but both locks still sit in the same groove at the same level. A single high lock is not seated in the groove.
D. Stem wear in the guide area is below the lock groove and does not change how the locks sit in the retainer. A lock that sits higher than its partner is not seated in the stem groove.
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On an engine with mechanical (solid) lifters, any of these could cause an exhaust valve to burn EXCEPT:
- valve clearance larger than the specification.
- a valve stem that sticks in its guide.
- a valve spring that has lost much of its tension.
- carbon deposits holding the valve off its seat.
Show the answer
A. Correct. Extra clearance makes the valve open later and close earlier, so it spends more time on its seat, where it passes heat to the head; the result is noise and wear, not burning. Clearance that is too tight is the condition that can hold a valve open and burn it.
Why not the others
B. A stem that sticks can hold the valve slightly open, so it cannot seat and cool, and burning follows. The exception is clearance larger than specified, which lets the valve close fully and stay closed longer.
C. A weak spring may not close the valve firmly or keep it closed at speed, so it seats poorly and runs hot, which can burn it. Excess clearance is the exception, since it lets the valve sit closed longer.
D. Deposits that keep the valve from closing let hot gas leak past the face and stop the valve from shedding heat into the seat, so it can burn. Clearance larger than specified is the exception: it keeps the valve on its seat longer.
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To replace the valve stem seals on one cylinder without removing the cylinder head, a technician removes that cylinder's spark plug and rocker arms and brings its piston to top dead center. What holds the valves closed while their springs are off?
- The new stem seal gripping the valve stem
- The spring compressor's hold on the retainer and locks
- The air pressure fed in through the spark plug hole
- The piston crown sitting under the valve heads
Show the answer
C. Correct. Regulated shop air through an adapter in the spark plug hole presses both valves against their seats while the springs, locks and seals are changed. With the piston at top dead center the air has almost no leverage to turn the crankshaft, and if pressure is lost the valve can drop only as far as the piston crown.
Why not the others
A. A stem seal is a light oil seal that the stem slides through; it cannot hold up a valve, and it is the part being replaced. Shop air pressure in the cylinder holds the valves against their seats.
B. The compressor holds the retainer down against the spring; once the locks are out, nothing on the compressor holds the valve, and it falls into the cylinder. Air pressure in the cylinder is what holds the valves up.
D. With the piston at top dead center the crown only limits how far a valve can drop if the air is lost; with its spring off, the valve would slide down off its seat until it touched the crown, so the piston does not hold it closed. Shop air fed through the spark plug hole holds both valves on their seats.
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On a pushrod engine with hydraulic lifters and adjustable rocker arms, the manufacturer's procedure is to tighten each rocker nut to zero lash with the lifter on its base circle, then turn it a further three-quarters of a turn. What does that extra turn set?
- The lifter plunger's depth in its body
- The valve spring's installed height
- The hot running clearance at the valve tip
- The rocker arm ratio at the valve
Show the answer
A. Correct. Past zero lash, the extra turn pushes the lifter's plunger part way down its travel, which is the preload; the lifter can then extend or retract to take up wear and expansion while keeping zero lash. Too little preload leaves the lifter noisy; too much can hold the valve open.
Why not the others
B. Installed height is set by the valve, seat, retainer and any spring shims, not by the rocker nut. The extra turn past zero lash sets the lifter plunger's depth, its preload.
C. A hydraulic lifter runs at zero lash hot and cold, so there is no running clearance to set. The extra turn past zero lash pushes the plunger down into the lifter body to give it preload.
D. Rocker ratio is fixed by the rocker arm's design, the distances from its pivot to each end. The extra turn past zero lash sets how far the lifter plunger sits down in its body, the preload.
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When flat-tappet hydraulic lifters are reused with the original camshaft in a pushrod engine, why must each go back into the bore it came from?
- Its length sets the lash for that valve
- Its plunger is set for that bore's oil feed
- Its face has worn in to match its own lobe
- Its check valve is matched to that valve spring
Show the answer
C. Correct. A flat-tappet lifter's face and its lobe wear in to each other, so a reused lifter goes back on the same lobe; on a different lobe the mismatched surfaces can wear the lobe away quickly. For the same reason a new camshaft gets new lifters.
Why not the others
A. A hydraulic lifter takes up lash itself, and its length is not matched to one valve. Lifters are kept in order because each face has worn in to the lobe it ran on.
B. The lifter bores are all fed from the lifter oil galleries at the same engine oil pressure, and a plunger does not adjust itself to one bore's supply. The reason to keep lifters in order is that each face has worn in to its own lobe.
D. Lifter check valves are not matched to individual springs; any good lifter of the right part works with any spring of the set. Lifters go back in order because each face has worn in to its own lobe.
02Answer key
| Question | Answer |
|---|---|
| Q1 | B |
| Q2 | A |
| Q3 | C |
| Q4 | A |
| Q5 | C |
03What area B covers
This content area covers the cylinder head and the parts that open and close the valves. Questions deal with cleaning heads and checking them for cracks and warpage, valves, seats, springs, locks and guides, valve lash and lifter preload, cam lobes and cam drives, valve timing, variable valve timing and lift parts, head gaskets and head bolts, and cam-driven pumps.
The ASE test specification calls this content area “Cylinder Head and Valve Train Diagnosis and Repair”. It carries 6 of the 45 scored questions, 13.3% of the test.
- Clean heads and check for cracks and warpage
- Inspect valves, seats, springs, locks and guides
- Replace valve stem seals
- Check pushrods, rockers, lifters and valve lash
- Inspect cam lobes, journals, bores and cam drives
- Set valve timing and check VVT and VVL parts
- Install head gaskets and tighten head bolts
- Service core plugs and cam-driven pumps
04What the questions turn on
Crack checks depend on the metal
Magnetic particle inspection relies on a magnetic field, so it works only on iron and steel parts. An aluminum head is checked for cracks with dye penetrant, a pressure test of the water jackets or close visual inspection with magnification.
Tight lash burns valves
With solid lifters, extra valve clearance shortens the time the valve is open, so it sits on its seat longer and sheds heat to the head; the result is noise and wear. Clearance that is too tight can hold a valve open and burn it.
Clearance is bore minus stem
Stem-to-guide clearance is the guide bore minus the stem diameter, taken at the worst point. When the stem measures within its own range but the clearance is over the limit, the guide is the worn part and is reconditioned or replaced.
Angle steps set bolt stretch
Much of a bolt's torque is spent on thread and underhead friction, which varies, so equal torque can give unequal clamp load. A torque-to-yield procedure turns a set angle after a low snug torque so each head bolt stretches about the same amount.
05The other content areas
The A1 test has five content areas. Each has its own page of free questions:
The ASE A1 Engine Repair practice test page describes the full question bank. How these questions are written and checked: how our questions are made. Found a mistake? Tell us and we will fix it.
ToolboxPrep is an independent study site. It is not affiliated with or endorsed by ASE (the National Institute for Automotive Service Excellence). Our questions are original practice questions written to the published ASE test specifications; they are not actual test questions.