Pontiac FIREBIRD 1972 Service Manual page 563

V-8 ENGINE 6-5 1
Fig. 6-84 Valve Train
the hydraulic lifter and push rod to the rocker arm. The
rocker arm pivots on its ball and transmits the camshaft
motion to the valve. The rocker arm ball is retained by a
nut which locks against a chamfer on the stud.
The maximum in durability is assured by the use of carbu-
rized and cyanide-hardened stamped steel rocker arms. In
addition, all friction points in the valve train are positively
lubricated.
The cylinder head has straight valve guides cast integrally
(Fig. 6-85). External shields are used on both intake and
exhaust valve springs to reduce the amount of oil splashed
against stems. (The WK engine does not incorporate
shields
-
see Fig. 6-1). Valve stem seals are used on exhaust
as well as intake valves to prevent excessive oil from enter-
ing the valve guides; in addition, umbrella type seals are
used on the intake valves of all 400 4 Bbl. and all 455
engines.
All V-8 engines use the large exhaust valves, formerly used
only in 400 and 455 4 Bbl. engines. Intake valves are of
two sizes
-
large and small. The small intake valve size is
used in all V-8 engines except 400 4 Bbl., 455 4 Bbl., and
455 H.O.
The 307 engine uses positive valve rotators on exhaust
valves only (Fig. 6-1 17). The rotators provide positive
valve rotation, insuring uniform seating and extended
valve life.
HYDRAULIC VALVE LIFTERS
Hydraulic lifters are used to keep all parts of the valve
VALVE GUIDES
I
CAST INTEGRAL
WITH CYLINDER
Fig. 6-85 lhtake Valve Guide
train in constant contact (Fig. 6-86 and 6-87). Each lifter
is an automatic adjuster maintaining zero lash under all
conditions. This insures precision valve timing and silent
operation, increases valve life, and eliminates the need for
tappet adjustment.
Two different types of hydraulic lifters, as shown in Figs.
6-86 and 6-87, are used in V-8 engines. For correct usage,
see Fig. 6-1.
The hydraulic lifter assembly includes: the cast iron body
which rides in the cylinder block boss, the plunger, push
rod seat, plunger spring, ball check valve and spring, ball
check valve retainer, rocker feed metering valve and re-
tainer ring.
RETAINER,
RING
ROCKER FEED
METERING VALVE.
BALL CHECK
I
VALVE
PLUNGER
SPRING
/
-
PUSH ROD
SEAT
PLUNGER
-
BALL CHECK
VALVE RETA
Fig. 6 - 8 6 Valve Lifter
-
Low Ball Type