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W o r n valve guides or cocked s p r i n g s are some-
times mistaken for noisy tappets. If such is the
case, noise may be dampened b y applying side
t h r u s t o n the valve spring. I f n o i s e i s not appre-
c i a b l y r e d u c e d , it c a n b e a s s u m e d the noise is in
the tappet. I n s p e c t t h e r o c k e r a r m p u s h rod
sockets a n d p u s h r o d e n d s for w e a r .
(3) Valve tappet noise ranges from l i g h t noise t o a
heavy click. A l i g h t noise is usually caused b y exces-
sive leak down a r o u n d t h e u n i t plunger w h i c h w i l l
necessitate replacing t h e tappet, o r b y t h e plunger
p a r t i a l l y s t i c k i n g i n t h e tappet body cylinder. A
heavy click is caused either b y a tappet check valve
not seating, or b y foreign particles becoming wedged
between t h e p l u n g e r a n d t h e tappet body, causing
the plunger t o stick i n t h e down position. T h i s heavy
click w i l l be accompanied b y excessive clearance be-
tween the valve stem a n d rocker a r m as valve closes.
I n either case, tappet assembly should be removed
for inspection and cleaning.
REMOVAL
(1) Remove valve cover a n d rocker assembly a n d
push rods a n d i d e n t i f y push rods t o ensure i n s t a l l a -
t i o n i n o r i g i n a l location.
(2) Remove i n t a k e m a n i f o l d , yoke retainer a n d
a l i g n i n g yokes (Fig. 1).
(3) Slide Tool C-4129 t h r o u g h opening i n cylinder
head and seat tool f i r m l y i n t h e head o f tappet.
(4) P u l l tappet out o f bore w i t h a t w i s t i n g m o t i o n .
I f a l l tappets are t o be removed, identify tappets t o
ensure i n s t a l l a t i o n i n o r i g i n a l location.
(5) I f the tappet or bore i n cylinder block is scored,
scuffed, or shows signs o f s t i c k i n g , r e a m the bore to
next oversize and replace w i t h oversize tappet.
CAUTION: The plunger and tappet bodies are not
interchangeable. The plunger and valve must al-
ways be fitted to the original body. It is advisable to
work on one tappet at a time to avoid mixing of
parts.Mixed parts are not compatible. Do not disas-
semble a tappet on a dirty work bench.
DISASSEMBLY
(1) Pry out plunger r e t a i n e r s p r i n g clip.
(2) Clean v a r n i s h deposits f r o m inside o f tappet
body above plunger cap.
(3) I n v e r t tappet body a n d remove plunger cap,
plunger, check valve, check valve spring, check valve
retainer a n d plunger spring. Check valve could be
flat or ball.
CLEANING
AND
ASSEMBLY
(1) Clean a l l tappet parts i n a solvent t h a t w i l l re-
move a l l v a r n i s h and carbon.
(2) Replace tappets t h a t are u n f i t for f u r t h e r ser-
vice w i t h new assemblies.
(3) I f plunger shows signs o f scoring or wear a n d
valve is p i t t e d , or i f valve seat o n end o f plunger i n -
dicates a n y condition t h a t w o u l d prevent valve from
seating, i n s t a l l a n e w tappet assembly.
(4) Assemble tappets (Fig. 2).
PLUNGER
SPRING
CHECK
BALL
PLUNGER
RETAINER
SPRING CLIP
ROLLER
TAPPET
BODY
CHECK VALVE
SPRING
PLUNGER
CAP
RK637
Fig. 2 Hydraulic Tappet Assembly
INSTALLATION
(1) L u b r i c a t e tappets.
(2) I n s t a l l tappets i n t h e i r o r i g i n a l positions.
(3) W i t h roller tappets, i n s t a l l a l i g n i n g yokes w i t h
A R R O W t o w a r d camshaft (Fig. 1).
(4) W i t h roller tappets, i n s t a l l yoke retainer a n d
t i g h t e n bolts t o 23 N
#
m (200 i n . lbs.) torque and i n -
s t a l l i n t a k e manifold (Fig. 1).
(5) I n s t a l l push rods i n o r i g i n a l positions.
(6) I n s t a l l rocker a r m and shaft assembly.
(7) I n s t a l l valve cover.
(8) S t a r t and operate engine. W a r m u p to n o r j m a l
operating temperature.
CAUTION: To prevent damage to valve mechanism,
engine must not be run above fast idle until all hy-
draulic tappets have filled with oil and have become
quiet.
VALVE TIMING
(1) T u r n crankshaft u n t i l t h e # 6 exhaust valve is
closing a n d # 6 i n t a k e valve is opening.
(2) I n s e r t a 6.350 m m (1/4 inch) spacer
between
rocker a r m pad and stem t i p o f # 1 i n t a k e valve. A l -
low s p r i n g load to bleed tappet down g i v i n g i n effect
a solid tappet.
(3) I n s t a l l a d i a l indicator so plunger contacts valve
spring r e t a i n e r as nearly perpendicular as possible.
Zero t h e indicator.
(4) Rotate t h e crankshaft clockwise (normal r u n -
n i n g direction) u n t i l t h e valve has lifted 0.254 m m
(0.010 inch).
CAUTION: Do not turn crankshaft any further clock-
wise as valve spring might bottom and result in se-
rious damage.
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