Valve Train

Question 1

Camshaft

Answer 1

Has eccentric lobes that rise off the center of the shaft to push on valve lifters or rocker arms and cause valves to open. Driven at half-crank speed by a timing chain, timing belt, or timing gears connected to the crankshaft. Many of today’s engines have 2 or 4 camshafts

Question 2

Valves

Answer 2

Intake valves are in the cylinder head. Valves allow the introduction of fuel & air into the engine by opening at the beginning od the intake stroke. Exhaust valves control the elongation of by-products of the combustion process. Both valves are closed during the compression and power strokes

Question 3

Timing Gears

Answer 3

Driven by the timing belt or a chain

Question 4

Timing Belt

Answer 4

Made of rubber with reinforcing bounds & teeth made of rubber to mesh with cam and crank gears

Question 5

Interference engines

Answer 5

If the timing belt brakes, then the valves will come on contact with the pistons. Critical to follow the mileage intervals recommended for belt replacement

Question 6

Non- interference engine

Answer 6

Engines that will not experience valve-to-piston contact if the timing belt breaks. Follow belt change intervals to avoid a break down & being towed to a repair shop

Question 7

Timing chain & gears

Answer 7

Do the same job as the timing belt. Not a maintenance item like the timing belt & are internal components that are lubricated by the engine lube oil system

Question 8

Timing belt tensioner

Answer 8

Provides proper pressure on the timing belt or in some cases, timing chain. Maybe spring-loaded, manually adjusted or actuated by engine oil pressure

Question 9

Camshaft Pulley Seals

Answer 9

Camshaft must have oil to lubricate it. These seals keep the oil in the engine & off the belt. Very commonly replaced compnent during timing belt service

Question 10

Front crank seal

Answer 10

Functions the same as a cam seal. It is in all engines. Can fail & is sometimes replaced during timing belt service

Question 11

Valve springs ans retainers

Answer 11

Valve springs apply closing pressure to the valves & help keep all moving parts in constant contact to avoid valve “float”. Retainers & keepers keep the valve springs in position in the valve stems

Question 12

Valve Cover

Answer 12

Cover that attaches to the cylinder head & covers the valve train components & overhead camshafts

Question 13

Cylinder head

Answer 13

Holds all of the valve train components & has passages for intake air & exhaust. Bolts onto the cylinder Blick & an intake & exhaust manifold or an intake & exhaust runner are bolted to it