1988 JEEP CHEROKEE length

Exhaust (1)
Head Diameter ................ 1.495-1.505 (37.97-38.60)
Face Angle ......................................... 44

Seat Angle ..................................... 44 30'
Seat Width ................... ( 2) .040-.060 (1.02-1.52)
Stem Diameter .................... .311-.312 (7.89-7.98)
Stem Clearance ..................... .001-.003 (.02-.08)
Valve Lift ................................ .424 (10.76)
( 1) - Minimum valve margin is 1/32" (.78 mm).
( 2) - Maximum seal runout is .0025" (.084 mm).









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PISTON/PIN/RING SPECIFICATIONS
PISTONS, PINS & RINGS SPECIFICATIONS TABLE








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Application In. (mm)
Piston Clearance ................. .0009-.0017 (.023-.043)
Pins
Piston Fit ..................... .0003-.0005 (.008-.013)
Rod Fit ...................................... Press Fit
Rings
Ring No. 1 & 2
End Gap .......................... .010-.020 (.25-.51)
Side Clearance ............... .0017-.0032 (.043-.081)
Ring No. 3
End Gap .......................... .010-.025 (.25-.64)
Side Clearance .................. .001-.008 (.03-.020)









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BEARING SPECIFICATIONS
CRANKSHAFT MAIN & CONNECTING ROD BEARINGS SPECS TABLE








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Application In. (mm)
Main Bearings
Journal Diameter ......... 2.4996-2.5001 (63.489-63.502)
Clearance ....................... .0010-.0025 (.02-.063)
Thrust Bearing ................................... No. 2
Crankshaft End Play ............ .0015-.0065 (.038-.165)
Connecting Rod Bearings
Journal Diameter ......... 2.0934-2.0955 (53.172-53.225)
Clearance .......................... .001-.003 (.02-.08)
Side Play .............................010-.019 (.02-.48)









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VALVE SPRING SPECIFICATIONS
VALVE SPRINGS SPECIFICATIONS TABLE








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Application In. (mm)
Free Length .................................. 1.82 (46.2)
Pressure ( 1)
Valve Closed ............... 66-74 @ 1.63 (30-34 @ 41.3)
Valve Open .............. 205-220 @ 1.20 (91-100 @ 30.5)
( 1) - Lbs. @ In. (Kg @ mm).









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fuel return line. The regulator is not controlled by the ECU. The
regulator's spring chamber is vented to the same pressure as the tip
of the injector.
Fig. 3: Cross Section View of Fuel Pressure Regulator
Since fuel pressure at the injector is kept constant, the
volume of fuel injected is dependent only on the length of time that
the injector is energized. The injection time duration is based on
engine operating conditions, which are provided to the ECU by the

Valve Closed ............ 66-74 @ 1.625 (30-34 @ 45.5)
Valve Open ........... 205-220 @ 1.20 (91-100 @ 30.48)
Free Length ............................... 1.82 (46.23)
4.2L
Pressure (1)
Valve Closed ............. 64-72 @ 1.79 (29-33 @ 45.5)
Valve Open ............. 188-202 @ 1.41 (85-92 @ 35.8)
Free Length ................................ 1.99 (50.5)
( 1) - Lbs. @ In. (Kg @ mm).









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DRIV E B ELT R O UTIN G

1988 J e ep C hero ke e
1983-88 ENGINE COOLING
Jeep Drive Belt Routing
Cherokee, Comanche, Wagoneer, Wrangler, Grand Wagoneer
DESCRIPTION
Two drive belt systems are used on Jeep vehicles. The
conventional V-Belt and the single Serpentine or V-Ribbed belt.
The single (Serpentine or V-Ribbed) drive belt system
has been adopted by several manufacturers as a replacement for
multiple V-Belt systems previously offered. The Serpentine belt
requires a suitable belt tensioner similar to those used to control
timing belt tension.
Use of a tensioner allows engine accessories to be mounted
rigidly on the engine. The single belt drive system has a predicted
life of 100,000 miles before replacement is required.
The belt tensioner has a wide functional range and is
capable of maintaining tension during the expected life of the belt.
Tensioner cannot compensate for extreme belt lengths. Poor tension
control and possible tensioner damage can result from excessive belt
length.
INSPECTION
Inspect belt for fraying. If fraying has occurred, ensure
belt and tensioner are aligned properly. See Fig. 1. If tensioner has
reached its limit of travel, belt is excessively stretched and
replacement of belt is required. If excessive noise is noticed from
tensioner or idler, check for possible bearing failure. Small cracks
in the back of the belt are acceptable. Do not apply "Belt Dressing"
or any other additive to serpentine belt.
Fig. 1: Serpentine Belt Alignment
Courtesy of Ford Motor Co.
DRIVE BELT ROUTING

NOTE: Always refer to appropriate engine overhaul article in the
ENGINES section for complete overhaul procedures and
specifications for the vehicle being repaired.
REMOVAL
Remove intake and exhaust manifolds and valve cover. Cylinder
head and camshaft carrier bolts (if equipped), should be removed only
when the engine is cold. On many aluminum cylinder heads, removal
while hot will cause cylinder head warpage. Mark rocker arm or
overhead cam components for location.
Remove rocker arm components or overhead cam components.
Components must be installed in original location. Individual design
rocker arms may utilize shafts, ball-type pedestal mounts or no rocker
arms. For all design types, wire components together and identify
according to the corresponding valve. Remove cylinder head bolts.
Note length and location. Some applications require cylinder head
bolts be removed in proper sequence to prevent cylinder head damage.
See Fig. 1 . Remove cylinder head.
Fig. 1: Typical Cylinder Head Tightening or Loosening Sequence
This Graphic For General Information Only
INSTALLATION
Ensure all surfaces and head bolts are clean. Check that head
bolt holes of cylinder block are clean and dry to prevent block damage
when bolts are tightened. Clean threads with tap to ensure accurate
bolt torque.
Install head gasket on cylinder block. Some manufacturer's
may recommend sealant be applied to head gasket prior to installation.
Note that all holes are aligned. Some gasket applications may be
marked so certain area faces upward. Install cylinder head using care
not to damage head gasket. Ensure cylinder head is fully seated on
cylinder block.
Some applications require head bolts be coated with sealant
prior to installation. This is done if head bolts are exposed to water
passages. Some applications require head bolts be coated with light
coat of engine oil.

Install head bolts. Head bolts should be tightened in proper
steps and sequence to specification. See Fig. 1. Install remaining
components. Tighten all bolts to specification. Adjust valves if
required. See VALVE ADJUSTMENT in this article.
NOTE: Some manufacturers require that head bolts be retightened
after specified amount of operation. This must be done to
prevent head gasket failure.
VALVE ADJUSTMENT
Engine specifications will indicate valve train clearance and
temperature at which adjustment is to be made on most models. In most
cases, adjustment will be made with a cold engine. In some cases, both
a cold and a hot clearance will be given for maintenance convenience.
On some models, adjustment is not required. Rocker arms are
tightened to specification and valve lash is automatically set. On
some models with push rod actuated valve train, adjustment is made at
push rod end of rocker arm while other models do not require
adjustment.
Clearance will be checked between tip of rocker arm and tip
of valve stem in proper sequence using a feeler gauge. Adjustment is
made by rotating adjusting screw until proper clearance is obtained.
Lock nut is then tightened. Engine will be rotated to obtain all valve
adjustments to manufacturer's specifications.
Some models require hydraulic lifter to be bled down and
clearance measured. Different length push rods can be used to obtain
proper clearance. Clearance will be checked between tip of rocker arm
and tip of valve stem in proper sequence using a feeler gauge.
On overhead cam engines designed without rocker arms actuate
valves directly on a cam follower. A hardened, removable disc is
installed between the cam lobe and lifter. Clearance will be checked
between cam heel and adjusting disc in proper sequence using a feeler
gauge. Engine will be rotated to obtain all valve adjustments.
On overhead cam engines designed with rocker arms, adjustment
is made at push rod end of rocker arm. Ensure that the valve to be
adjusted is riding on the heel of the cam on all engines. Clearance
will be checked between tip of rocker arm and tip of valve stem in
proper sequence using a feeler gauge. Adjustment is made by rotating
adjusting screw until proper clearance is obtained. Lock nut is then
tightened. Engine will be rotated to obtain all valve adjustments to
manufacturer's specifications.
CYLINDER HEAD OVERHAUL
* PLEASE READ THIS FIRST *
NOTE: Always refer to appropriate engine overhaul article in the
ENGINES section for complete overhaul procedures and
specifications for the vehicle being repaired.
DISASSEMBLY
Mark valves for location. Using valve spring compressor,
compress valve springs. Remove valve locks. Carefully release spring
compressor. Remove retainer or rotator, valve spring, spring seat and
valve. See Fig. 2.

On cast cylinder heads, if warpage exceeds .003" (.08 mm)
in a 6" span, or .006" (.15 mm) over total length, cylinder head must
be resurfaced. On most aluminum cylinder heads, if warpage exceeds .
002" (.05 mm) in any area, cylinder head must be resurfaced. Warpage
specification may vary with manufacturer.
Cylinder head thickness should be measured to determine
amount of material which can be removed before replacement is
required. Cylinder head thickness must not be less than manufacturer's
specifications.
If cylinder head required resurfacing, it may not align
properly with intake manifold. On "V" type engines, misalignment is
corrected by machining intake manifold surface that contacts cylinder
head. Cylinder head may be machined on surface that contacts intake
manifold.
Using oil stone, remove burrs or scratches from all sealing
surfaces.
VALVE SPRINGS
Inspect valve springs for corroded or pitted valve spring
surfaces which may lead to breakage. Polished spring ends caused by
a rotating spring, indicates that spring surge has occurred. Replace
springs showing evidence of these conditions.
Inspect valve springs for squareness using a 90 degree
straightedge. See Fig. 4. Replace valve spring if out-of-square
exceeds manufacturer's specification.
Fig. 4: Checking Valve Spring Squareness - Typical
This Graphic For General Information Only
Using vernier caliper, measure free length of all valve
springs. Replace springs if not within specification. Using valve

Fig. 6: Measuring Valve Stem-to-Guide Clearance - Typical
This Graphic For General Information Only
Lower valve approximately 1/16" below valve seat. Push valve
stem against valve guide as far as possible. Adjust dial indicator to
zero. Push valve stem in opposite direction and note reading.
Clearance must be within specification.
If valve guide clearance exceeds specification, valves with
oversize stems may be used or valve guide must be replaced. On some
applications, a false guide is installed, then reamed to proper
specification. Valve guide reamer set is used to ream valve guide to
obtain proper clearance for new valve.
Reaming Valve Guide
Select proper reamer for valve stem. Reamer must be of
proper length to provide clean cut through entire length of valve
guide. Install reamer in valve guide and rotate to cut valve guide.
See Fig. 7 .