Mitsubishi Montero (1998+). Manual - part 139

Fig. 2:  Exploded View of Intake & Exhaust Valve Assemblies - Typical

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         CLEANING & INSPECTION

         Clean cylinder head and valve components using approved

cleaning methods. Inspect cylinder head for cracks, damage or warped

gasket surface. Place straightedge across gasket surface. Determine

clearance at center of straightedge. Measure across both diagonals,

longitudinal centerline and across the head at several points. See

Fig. 3.

Fig. 3:  Checking Cylinder Head for Warpage - Typical

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         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

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         Using vernier caliper, measure free length of all valve

springs. Replace springs if not within specification. Using valve

spring tester, test valve spring pressure at installed and compressed

heights. See Fig. 5.

         Usually compressed height is installed height minus valve

lift. Replace valve spring if not within specification. It is

recommended to replace all valve springs when overhauling cylinder

head.

Fig. 5:  Checking Valve Spring Pressure - Typical

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         VALVE GUIDE

         Measuring Valve Guide Clearance

         Check valve stem-to-guide clearance. Ensure valve stem

diameter is within specifications. Install valve in valve guide.

Install dial indicator assembly on cylinder head with tip resting

against valve stem just above valve guide. See  Fig. 6.

Fig. 6:  Measuring Valve Stem-to-Guide Clearance - Typical

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         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.