1991 LEXUS SC300 oil

3. REMOVE ENGINE HANGERS
4. REMOVE ENGINE COOLANT TEMPERATURE SENSORAND SENDER GAUGE
5. REMOVE THROTTLE CABLE BRACKET AND GROUND STRAP
6. REMOVE EGR COOLER
INSPECTION, CLEANING AND REPAIR
OF CYLINDER HEAD COMPONENTS
1. CLEAN TOP SURFACES OF PISTONS AND CYLINDER BLOCK
(a) Turn the crankshaft, and bring each piston to top deadcenter (TDC). Using a gasket scraper, remove all the
carbon from the piston top surface.
(b) Using a gasket scraper, remove all the gasket material from the top surface of the cylinder block.
(c) Using compressed air, blow carbon and oil from the bolt
holes.
CAUTION: Protect your eyes when using high±com-
pressed air.
2. CLEAN CYLINDER HEAD
A. Remove gasket material Using a gasket scraper, remove all the gasket material from
the cylinder block surface.
NOTICE: Be careful not to scratch the cylinder block con-
tact surface.
EM±42
±
ENGINE MECHANICAL Cylinder Head
WhereEverybodyKnowsYourName

B. Inspect for cranksUsing a dye penetrant, check the combustion chamber, in-
take ports, exhaust ports and cylinder block surface for
cracks.
If cracked, replace the cylinder head.
4. CLEAN VALVES (a) Using a gasket scraper, chip off any carbon from thevalve head.
(b) Using a wire brush, thoroughly clean the valve.
5. INSPECT VALVE STEMS AND GUIDE BUSHINGS (a) Using a caliper gauge, measure the inside diameter ofthe guide bushing.
Bushing inside diameter:
6.010±6.030 mm (0.2366±0.2374 in.)
(b) Using a micrometer, measure the diameter of the valvestem.
Valve stem diameter:
Intake 5.970±5.985 mm (0.2350±0.2356 in.)
Exhaust 5.965±5.980 mm (0.2348±0.2354 in.)
(c) Subtract valve stem diameter measurement from theguide bushing inside diameter measurement.
Standard oil clearance:
Intake 0.025±0.060 mm
(0.0010±0.0024 in.)
Exhaust 0.030±0.065 mm (0.0012±0.0036 in.)
Maximum oil clearance:
Intake 0.08 mm (0.0031 in.)
Exhaust 0.10 mm (0.0039 in.)
If the clearance is greater than maximum, replace the valve
and guide bushing.
EM±44
±
ENGINE MECHANICAL Cylinder Head
WhereEverybodyKnowsYourName

B. Inspect cam lobesUsing a micrometer, measure the cam lobe height.
Standard cam lobe height:
Intake 44.570±44.670 mm (1.7547±1.7587 in.)
Exhaust 44.250±44.350 mm (1.7421±1.7461 in.)
Maximum cam lobe height: Intake 44.42 mm (1.7488 in.)
Exhaust 44.10 mm (1.7362 in.)
If the cam lobe height is less than minimum, replace the cam-
shaft.
C. Inspect camshaft journals Using a micrometer, measure the journal diameter.
Journal diameter: 28.949±28.965 mm
(1.1397±1.1404 in.)
If the journal diameter is not as specified, check the oil clear-
ance.
D. Inspect camshaft bearings Check the bearings for flaking and scoring.
If the bearings are damaged, replace the bearing caps and
cylinder head as a set.
E. Inspect camshaft journal oil clearance (a) Clean the bearing caps and camshaft journals.
(b) Place the camshafts on the cylinder head.
(c) Lay a strip of Plastigage across each of the camshaftjournals.
(d) Install the bearing caps. (See step 2 on page EM±55)
Torque: 20 N Vm (200 kgf Vcm, 14 ft Vlbf)
HINT: Do not turn the camshaft.
±
ENGINE MECHANICAL Cylinder HeadEM±49
WhereEverybodyKnowsYourName

(e) Remove the bearing caps.
(f) Measure the Plastigage at its widest point.
Standard oil clearance: 0.035±0.072 mm(0.0014±0.0028 in.)
Maximum oil clearance: 0.10 mm (0.039 in.)
If the oil clearance is greater than maximum, replace the cam-
shaft. If necessary, replace the bearing caps and cylinder
head as a set.
(g) Completely remove the Plastigage.
F. Inspect camshaft thrust clearance (a) Install the camshafts.
(See step 2 on page EM±55)
(b) Using a dial indicator, measure the thrust clearancewhile moving the camshaft back and forth.
Standard thrust clearance: 0.080±0.190 mm
(0.0031±0.0075 in.)
Maximum thrust clearance: 0.30 mm (0.0118 in.)
If the thrust clearance is greater than maximum, replace the
camshaft. If necessary, replace the bearing caps and cylin-
der head as a set.
11. INSPECT VALVE LIFTERS AND LIFTER BORES (a) Using a caliper gauge, measure the lifter bore diameterof the cylinder head.
Lifter bore diameter: 31.000±31.016 mm
(1.2205±1.2211 in.)
(b) Using a micrometer, measure the lifter diameter.
Lifter diameter: 30.966±30.976 mm(1.2191±1.2195 in.)
EM±50±
ENGINE MECHANICAL Cylinder Head
WhereEverybodyKnowsYourName

(c) Subtract the lifter diameter measurement from the lifterbore diameter measurement.
Standard oil clearance: 0.024±0.050 mm
(0.0009±0.0020 in.)
Maximum oil clearance: 0.07 mm (0.0028 in.)
If the oil clearance is greater than maximum, replace the lifter.
If necessary, replace the cylinder head.
12. INSPECT AIR INTAKE CHAMBER Using a precision straight edge and feeler gauge, measure
the surfaces contacting the intake manifold for warpage.
Maximum warpage: 0.15 mm (0.0059 in.)
If warpage is greater than maximum, replace the chamber.
13. INSPECT INTAKE MANIFOLD Using a precision straight edge and feeler gauge, measure
the surfaces contacting the cylinder head and air intake
chamber for warpage.
Maximum warpage: 0.15 mm (0.0059 in.)
If warpage is greater than maximum, replace the manifold.
14. INSPECT EXHAUST MANIFOLDS Using a precision straight edge and feeler gauge, measure
the surfaces contacting the cylinder head for warpage.
Maximum warpage: 0.8 mm (0.031 in.)
If warpage is greater than maximum, replace the manifold.
15. INSPECT CYLINDER HEAD BOLTS Using a vernier caliper, measure the thread outside diameter
of the bolt.
Standard outside diameter: 10.8±11.0 mm
(0.425±0.433 in.)
Minimum outside diameter: 10.7 mm (0.421 in.)
If the diameter is less than minimum, replace the bolt.
±
ENGINE MECHANICAL Cylinder HeadEM±51
WhereEverybodyKnowsYourName

ASSEMBLY OF CYLINDER HEAD
(See Components on page EM±35)HINT:
wThoroughly clean all parts to be assembled.
w Before installing the parts, apply new engine oil to all
sliding and rotating surfaces.
w Replace all gaskets and oil seals with new ones.
1. INSTALL HEATER UNION HINT: When using a new cylinder head, heater union must be
installed.
(a) Apply adhesive to the end of the heater union as shownin the illustration.
Adhesive: Part No. 08833±00070, THREE BOND 1324 or equivalent
(b) Using a wooden block and hammer, tap in a new heater
union, leaving 73 mm (2.87 in.) protruding from the
cylinder head.
NOTICE: Do not tap it in too far.
2. INSTALL EGR COOLER Install a new gasket and EGR cooler with the eight bolts.
Torque: 14 N Vm (140 kgf Vcm, 10 ft Vlbf)
3. INSTALL ENGINE COOLANT TEMPERATURE SENSOR
AND SENDER GAUGE
Torque: 20 N Vm (200 kgf Vcm, 14 ft Vlbf)
4. INSTALL GROUND STRAP AND THROTTLE CABLE
BRACKET
5. INSTALL ENGINE HANGERS
Torque: 39 N Vm (400 kgf Vcm, 29 ft Vlbf)
EM±52±
ENGINE MECHANICAL Cylinder Head
WhereEverybodyKnowsYourName

3. INSTALL VALVES(a) Install new oil seal on the valve guide bushing.
HINT: The intake valve oil seal is brown and the exhaust valve
oil seal is black.
(b) Install the following parts:(1) Valve
(2) Spring seat
(3) Valve spring
(4) Spring retainer
HINT: Install the valve spring, facing the painted mark up-
ward.
(c) Using SST, compress the valve spring and place the two
keepers around the valve stem.
SST 09202±70010
±
ENGINE MECHANICAL Cylinder HeadEM±53
WhereEverybodyKnowsYourName

(d) Using a plastic±faced hammer, lightly tap the valve stem
tip to assure proper fit.
4. INSTALL VALVE LIFTERS AND SHIMS (a) Install the valve lifter and shim.
(b) Check that the valve lifter rotates smoothly by hand.
INSTALLATION OF CYLINDER HEAD
(See Components on pages EM±34 and 35)1. INSTALL CYLINDER HEAD
A. Place cylinder head on cylinder block (a) Place a new cylinder head gasket in position on thecylinder block.
NOTICE: Be sure to install it correctly.
(b) Place the cylinder head in position on the cylinder head
gasket and connect the heater water hose to the union.
B. Install cylinder head bolts
HINT:
wThe cylinder head bolts are tightened in two progressive
steps (steps (c) and (f)).
w If any of bolts break or deform, replace them.
(a) Apply a light coat of engine oil on the threads and under
the heads of the cylinder head bolts.
(b) Install the 14 plate washers to each cylinder head bolt.
(c) First, using a 10 mm bi±hexagon wrench, uniformly tighten the cylinder head bolts in several passes in the
sequence shown.
Torque: 34 N Vm (350 kgf Vcm, 25 ft Vlbf)
If any one of the bolts does not meet the torque specification,
replace the bolt.
EM±54
±
ENGINE MECHANICAL Cylinder Head
WhereEverybodyKnowsYourName