Pontiac FIREBIRD 1972 Service Manual page 517

ENGINE-MECHANICAL
6-5
1
NOISY PISTONSAND RINGS
CAUSE
a. Excessive clearance between piston and bore. d. Connecting rods improperly aligned.
b. Improper fit of piston pin.
e. Excessive clearance between rings and grooves.
c. Excessive accumulation of carbon in heads.
f.
Rings broken.
BROKEN PISTONS AND/OR RINGS
CAUSE
a. Undersize pistons installed.
f. Pins improperly assembled.
b. Wrong type and/or size rings installed.
g. Insufficient ring gap clearance.
,
c. Cylinder bores tapered or eccentric.
h. Engine overheating.
d. Connecting rods improperly aligned.
i. Fuel of too low octane rating.
e. Excessively worn ring grooves.
NOISY CONNECTING RODS
CAUSE
a. Connecting rods improperly aligned.
d. Insufficient oil supply.
b. Excessive bearing clearance.
e. Low oil pressure.
c. Eccentric or out-of-round crankshaft journals.
f. Connecting rod bolts not tightened correctly.
NOISY M A I N BEARINGS
CAUSE
a. Low oil pressure and/or insufficient oil supply.
e. Sprung crankshaft.
b. Excessive bearing clearance.
f. Excessive belt tension.
c. Excessive crankshaft end play.
g. Loose harmonic balancer.
d. Eccentric or out-of-round crankshaft journals.
NOISY VALVE LIFTERS
CAUSE
a. Broken valve springs.
g. Excessively worn camshaft lobes.
b. Worn or sticking rocker arms.
c. Worn or bent push rods.
d. Valve lifters incorrectly fitted to bore size.
h. Valve lifter oil feed holes plugged causing interns
breakdown.
i. Faulty valve lifter check ball. (Nicked, flat spot, or ou
'
of round.
e. Faulty valve lifter plunger or push rod seat.
j. Rocker arm retaining nut installed upside down.
f. Plungers excessively worn causing fast leakdown under
k. End of push rod excessively worn or flaked.
pressure.