Chapter 12 Engine Repair: Upper End Theory and Service

TRUE OR FALSE: A cylinder head may be made of cast iron or aluminum.

TRUE

TRUE OR FALSE: Aluminum cylinder head bolts should never be loosened or tightened when the metal is hot.

TRUE

TRUE OR FALSE: Aluminum cylinder heads weigh roughly half as much as cast-iron heads.

TRUE

TRUE OR FALSE: Aluminum expands and contracts almost twice as much as cast iron in response to temperature changes.

TRUE

TRUE OR FALSE: Many camshaft journals run directly on aluminum supports and do not use bearing inserts.

TRUE

TRUE OR FALSE: Resurfacing a cylinder head gasket surface may alter the combustion chamber volume.

TRUE

TRUE OR FALSE: Stainless steel is nonmagnetic.

TRUE

TRUE OR FALSE: To protect against scuffing and wear, some valves have coatings of black nitride applied to the valve stem.

TRUE

Technician A says heat is transferred from an exhaust valve to the cylinder head through the valve seat. Technician B says some exhaust valves have a hollow stem filled with silicone to transfer heat to the valve guide. Who is correct? A) A only B) B only C) both A and B D) neither A nor B

A) A only

Technician A says if valve stem height exceeds specifications, it can be adjusted by grinding the valve tip. Technician B says the valve stem height can be adjusted with shims. Who is correct? A) A only B) B only C) both A and B D) neither A nor B

A) A only

Technician A uses a 30-degree stone for topping a 45-degree valve seat. Technician B uses a 60-degree stone to lower a 45-degree valve seat. Who is correct? A) A only B) B only C) both A and B D) neither A nor B

A) A only

After resurfacing a valve seat at 45 degrees, the seat is too wide and the contact pattern extends all the way up to the valve margin. What should be done to bring the seat width into specifications? A) Make a 30-degree topping cut B) Make a 45-degree seat cut C) Make a 60-degree throat cut D) Replace the valve

A) Make a 30-degree topping cut

Cylinder head warpage can be measured with _____. A) a straightedge and feeler gauge B) a dial indicator C) a surface gauge D) a ball gauge and outside micrometer

A) a straightedge and feeler gauge

A typical interference angle is _____ degree(s). A) 30 B) 1 C) 45 D) 46

B) 1

Technician A says the end of the valve spring that is wound the tightest should face toward the spring retainer. Technician B says the O-ring seal should be installed in the lowest of the keeper grooves on the valve stem. A) A only B) B only C) both A and B D) neither A nor B

B) B only

Technician A says the valve seats must be ground before the valve guides are serviced. Technician B says before grinding the valve seats, they should be checked for cracks. Who is correct? A) A only B) B only C) both A and B D) neither A nor B

B) B only

_____type valve stem seals move up and down with the valve stems to deflect oil away from the guides. A) Positive B) Umbrella C) O-ring D) Lip

B) Umbrella

Which type of surfacing machine uses underside rotary cutters? A) milling B) broaching C) belt D) grinding

B) broaching

Induction-hardened integral valve seats are found on _____ cylinder heads. A) aluminum B) cast iron C) both "aluminum" and "cast iron" D) neither "aluminum" nor "cast iron"

B) cast iron

A pentroof combustion chamber is normally found on a(n) _____type cylinder head. A) OHV B) four valve per cylinder C) two valve per cylinder D) VVT [variable valve timing]

B) four valve per cylinder

A single hole in the cylinder head that divides into two branches is called a _____ port. A) dual B) siamese C) combination D) two-stage

B) siamese

What is typically the maximum amount of warpage that is acceptable on a cast-iron cylinder head? A) 0.002 in. (.05 mm) B) 0.003 in. (.076 mm) C) 0.004 in. (.102 mm) D) 0.005 in. (.127 mm)

C) 0.004 in. (.102 mm)

Which of the following is NOT true of knurling? A) It is one of the fastest techniques for restoring the inside diameter (ID) dimension of a worn valve guide B) It reduces the amount of work necessary to reseat the valve C) It is useful for restoring badly worn guides to their original condition D) None of these answers is correct

C) It is useful for restoring badly worn guides to their original condition

Which of the following can be reconditioned by grinding? A) valve face B) valve tip C) both "valve face" and "valve tip" D) neither both "valve face" nor "valve tip"

C) both "valve face" and "valve tip"

Hemispherical combustion chambers are being discussed. Technician A says the flame path from the spark plug to the piston head is short, which provides efficient burning. Technician B says cross-flow arrangement of the inlet and exhaust valves allows for a relatively free flow of gases in and out of the chamber. Who is correct? A) A only B) B only C) both A and B D) neither A nor B

C) both A and B

Technician A checks for bent pushrods by rolling them on a flat surface. Technician B checks for bent pushrods using a dial indicator and V-blocks. Who is correct? A) A only B) B only C) both A and B D) neither A nor B

C) both A and B

Technician A resurfaces valve seats using a grinding stone. Technician B resurfaces valve seats using a cutting blade. Who is correct? A) A only B) B only C) both A and B D) neither A nor B

C) both A and B

Technician A says VVT [variable valve timing] engines use a cam phaser that advances or retards the camshaft as the engine is running. Technician B says VVT engines use a third cam lobe with increased lift and duration, operating a third rocker arm that is coupled to the two primary rocker arms by a hydraulically controlled pin, while the engine is running. Who is correct? A) A only B) B only C) both A and B D) neither A nor B

C) both A and B

Technician A says multivalve engines can have three valves per cylinder. Technician B says multivalve engines can have five valves per cylinder. Who is correct? A) A only B) B only C) both A and B D) neither A nor B

C) both A and B

Technician A says multivalve engines have a more complete combustion than conventional engine designs. Technician B says the benefits of multivalve engines are offset to some extent because a more complicated camshaft arrangement is needed. Who is correct? A) A only B) B only C) both A and B D) neither A nor B

C) both A and B

Technician A says positive valve stem seals fit tightly around the top of the stem. Technician B says positive stem seals scrape oil off the valve as it moves up and down. Who is correct? A) A only B) B only C) both A and B D) neither A nor B

C) both A and B

Technician A says worn valve stem seals can increase oil consumption. Technician B says worn valve stem seals can cause valve deposits. Who is correct? A) A only B) B only C) both A and B D) neither A nor B

C) both A and B

Valve springs should be checked for all of the following EXCEPT: A) freestanding height B) squareness C) compressed height D) open pressure

C) compressed height

Multiple valve engines tend to be more efficient than engines with two valves per cylinder because: A) larger valve area improves the air flow in and out of the cylinder B) air velocity is increased—especially at low engine speed; this increases air flow C) smaller and lighter valves require less spring tension—less engine power is lost to spring opening drag D) all answers are correct

D) all answers are correct

Resurfacing the cylinder head can affect _____. A) compression ratio B) valve timing C) piston to valve clearance D) all answers are correct

D) all answers are correct

To ensure proper seating of the valve, the valve seat must _____. A) be the correct width B) have the correct location on the valve face C) be concentric with the guide D) all answers are correct

D) all answers are correct

Valve guides are _____. A) integral [bores in cylinder head] B) pressed in cast iron inserts C) pressed in bronze inserts D) all answers are correct

D) all answers are correct

Prussian blue or machinist dye is used to ______. A) measure stem-to-guide clearance B) measure valve runout C) mark the position of cam bearings prior to removal D) check the width and position of the valve-to-seat contact pattern

D) check the width and position of the valve-to-seat contact pattern

TRUE OR FALSE: Powder metal valve seats are softer and do not last as long as cast iron seats.

FALSE

TRUE OR FALSE: Sodium-filled valves should be cut open for inspection.

FALSE

TRUE OR FALSE: The hemispherical combustion chamber provides excellent turbulence to the air and fuel mixture.

FALSE

TRUE OR FALSE: The performance of an engine, its fuel efficiency, and its exhaust emissions all depend to a large extent on the shape of the combustion chamber.

TRUE