Pontiac FIREBIRD 1972 Service Manual page 516

6-4 1972 PONTIAC SERVICE MANUAL
EXCESSIVE OIL CONSUMPTION DUE TO OIL ENTERING
COMBUSTION CHAMBER BY PASSING PISTON RINGS
CAUSE
a. Oil level too high.
g. Ring grooves or oil return slots clogged.
b. Excessive main or connecting rod bearing clearance.
h. Rings sticking in ring grooves of piston.
c. Piston ring gaps not staggered.
i. Ring grooves worn excessively in piston.
d. Incorrect size rings installed.
e. Piston rings out of round, broken or scored.
j. Compression rings installed upside down.
k. Excessively worn or scored cylinder walls.
f. Insufficient piston ring tension due to engine overheat-
1. Oil too thin.
ing.
N O OIL PRESSURE WHILE IDLING
CAUSE
a. Faulty oil gauge sending unit.
d. Loose camshaft bearings.
b. Oil pump not functioning properly. (Regulator ball
e. Leakage at internal oil passages.
stuck in position by foreign material).
c. Excessive clearance at main and connecting rod bear-
ings.
N O OIL PRESSURE WHILE ACCELERATING
CAUSE
a. Low oil level in oil pan.
b. Leakage at internal oil passages.
BURNED, STICKING OR BROKEN VALVES
CAUSE
a. Weak valve springs.
e. Deposits on valve seats and/or gum formation on stems
or guides.
b. Improper valve lifter clearance.
f. Warped valves or faulty valve forgings.
c. Improper valve guide clearance and/or worn valve
guides. g. Exhaust back pressure.
d. Out-of-round valve seats or incorrect valve seat width.
h. Improper spark timing.
NOISY VALVES
CAUSE
a. Incorrect valve lifter clearance.
e. Worn .camshaft lobes.
b. Excessively worn, dirty or faulty valve lifters.
f. Pulled or loose rocker arm studs.
c. Worn valve guides.
g. Bent push rods.
d. Excessive run-out of valve seat or valve face.