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measured halfway down the cylinder bore and trans-
verse t o t h e engine crankshaft center l i n e .
P i s t o n s
a n d c y l i n d e r b o r e s
s h o u l d b e m e a -
s u r e d a t n o r m a l r o o m t e m p e r a t u r e , 21°C (70°F).
PISTON
PINS
The p i s t o n p i n rotates i n t h e piston only, a n d is re-
t a i n e d b y t h e press interference f i t o f the piston p i n
i n t h e connecting rod.
FITTING
RINGS
(1) Measure piston r i n g gap about t w o inches f r o m
bottom o f cylinder bore i n w h i c h i t is t o befitted ( A n
i n v e r t e d piston can be used to push the r i n g s down t o
insure p o s i t i o n i n g r i n g s squarely i n the cylinder bore
before measuring).
(2) I n s e r t feeler stock i n t h e gap. T h e r i n g gap
should be between 0.254 and 0.508 m m (0.010 and
0.020 inch) for compression rings and 0.381 t o 1.575
m m (0.015 t o 0.062 inch) for o i l r i n g steel r a i l s i n
standard size bores (for new service r i n g s ) . M a x i m u m
gap i n 0.127 m m (0.005 inch) O/S bores should be
0.907 m m (0.036 inch) for compression r i n g s a n d
1.778 m m (0.070 inch) for o i l r i n g steel r a i l s .
(3) Measure side clearance between piston r i n g and
r i n g l a n d (Fig. 3). Clearance should be 0.038 t o 0.076
m m (0.0015 t o 0.003 inch) for t h e top compression
r i n g a n d t h e intermediate r i n g . Steel r a i l service o i l
r i n g should be free i n groove, b u t should not exceed
0.127 m m (0.005 inch) side clearance.
PISTON RING
FEELER GAUGE
RH166"
Fig. 3 Measuring Piston Ring Side Clearance
(4) O n the 3.9L engine, the keys o n the spacer ex-
pander m u s t be inserted into the hole i n the o i l r i n g
groove over the piston p i n front boss (Fig. 4).
(5) A r r a n g e o i l r i n g r a i l gaps on inboard side o f
piston (Top of F i g . 4).
(6) I n s t a l l compression rings i n middle a n d top
grooves u s i n g R i n g Installer Tool C-4184. Be sure
the compression r i n g identification m a r k (a d r i l l
point, a stamped letter " O " , a n oval depression or t h e
w o r d top) i s t o the top o f the piston.
CONNECTING RODS
INSTALLATION
PISTON AND
CONNECTING
ROD
ASSEMBLY
(1) Before i n s t a l l i n g pistons, a n d connecting r o d as-
semblies i n t o the bore, be sure t h a t compression r i n g
gaps are staggered so t h a t n e i t h e r is i n l i n e w i t h o i l
r i n g r a i l gap.
(2) Before
i n s t a l l i n g t h e r i n g compressor,
m a k e
sure t h e o i l r i n g expander ends are b u t t e d and t h e
r a i l gaps located properly (Fig. 4).
(3) Immerse the piston head a n d r i n g s i n clean en-
gine o i l . Slide the r i n g compressor (Tool C-385) over
the piston and t i g h t e n w i t h the special wrench ( p a r t
of Tool C-385). B e s u r e p o s i t i o n o f r i n g s does n o t
c h a n g e d u r i n g t h i s o p e r a t i o n .
(4) I n s t a l l connecting r o d b o l t protectors on r o d
bolts, t h e l o n g protector should be i n s t a l l e d o n t h e
numbered side of the connecting rod.
(5) Rotate crankshaft so t h a t t h e connecting r o d
j o u r n a l is o n the center o f t h e c y l i n d e r bore. I n s e r t
rod a n d piston i n t o cylinder bore a n d guide rod over
the c r a n k s h a f t j o u r n a l .
TOP VIEW OF BLOCK
A-EXPANDER GAPS
B-RAIL GAPS
IF YOU HAVE FOLLOWED THE
INSTRUCTIONS, THE RING WILL BE
IN THIS POSITION ON THE PISTON.
TOP RAIL GAP-
ENDS
BUTTING
BOTTOM
RAIL GAP
RP137
Fig. 4 Proper Oil Ring Installation
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