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EXERCICIO DE INGLS 24-07-12

PANTOJA 03

IONTA - 15

1 PISTONS

Piston wears - Piston wear is characterized by an excessive clearance between thepiston and the cylinder. Symptoms of excessive clearance between a piston and

cylinder are piston slap and excessive oil consumption.

Crack - Cracking of the lands of a piston is caused by insufficient ring groove clearance Seizure New pistons or liners must be installed with the piston-to-cylinder clearances

specified in the manufacturers technical manual. The resulting excess surface

temperatures may lead to seizure or breakage.

2 RING PISTONS

Excessive oil consumption - is generally associated with worn oil rings. Two factors that cause improper ring clearance are: Abnormal amount of carbon

deposits on rings and in grooves. Improper dimensions. New rings must have the

proper thickness, width, diameter, and gap.

One cause of undue loads on a ring could be insufficient gap clearance. This conditionwould cause the ring to be forced out and into a port of a ported cylinder, and possibly

result in breakage.

3 - PISTON PINS AND PIN BEARINGS

Excessive wear of pins, bushings, or bearings is often the result of insufficient orimproper lubrication. (These parts are usually pressure lubricated.) The failure of a

pressure lubricating system is usually detected before piston pins, bushings, or

bearings are seriously damaged.

Insufficient lubrication of these parts is usually caused by obstructions blocking the oilpassages of the connecting rods

Misalignment may be caused by improper reaming of the bushing for properclearance.

4 - CONNECTING RODS

Misalignment causes binding of the piston, piston pin, and the connecting rod journalbearing.

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Cracked rods are usually the result of overstressing caused by overloading oroverspeeding or because defective material was used at the time of manufacture.

Defective bolts are often the result of overtightening.

5 - SHAFTS AND BEARINGS

Fatigue failure of journal bearings in internal combustion engines is usually caused bycyclic peak loads.

Severe overloading or overspeeding of an engine increases fatigue failure. Operation of an engine at critical torsional speeds and in excess of the rated speed will

lead to engine shaft and bearing difficulties.

6- CRANKSHAFTS

Journal bearing failures may cause not only scoring but also broken or bent crankshaftsand out-of-round journals.

Broken or bent crankshafts may be caused by the improper functioning of a torsionalvibration damper.

Excessive rumbling at certain engine speeds may indicate that the damper is notfunctioning properly.

7 CAMSHAFTS

Valves must be timed correctly at all times, not only for the proper operation of theengine but also to prevent possible damage to the engine parts.

Cams damaged result in scoring or breaking of the cams and followers, as well assevere damage to the piston and the cylinder.

taking tappet clearances and adjusting checking for broken, chipped, or improperlyseated valve springs;