Lexus SC300 / Lexus SC400. Service manual — part 403

HINT:

•

The piston and pin are a matched set.

•

Arrange the pistons, pins, rings, connecting rods and
bearings in correct order.

INSPECTION OF PISTON AND
CONNECTING ROD ASSEMBLIES

1. CLEAN

PISTON

(a) Using a gasket scraper, remove the carbon from the

piston top.

(b) Using a groove cleaning tool or broken ring, clean the

piston ring grooves.

(c) Using solvent and a brush, thoroughly clean the piston.
NOTICE: Do not use a wire brush.

EM–146

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ENGINE MECHANICAL

Cylinder Block

2. INSPECT

PISTON

A.

Inspect piston oil clearance
HINT: There are three sizes of the standard piston, marked
”1”, ”2” and ”3” accordingly. The mark is stamped on the top
of the piston.
(a) Using a micrometer, measure the piston diameter at

right angles to the piston pin center line, 49 mm (1.93 in.)
from the piston head.

Piston diameter:

Mark ”1” 87.470–87.480 mm

(3.4437–3.4441 in.)

Mark ”2” 87.480–87.490 mm

(3.4441–3.4445 in.)

Mark ”3” 87.490–87.500 mm

(3.4445–3.4449 in.)

(b) Measure the cylinder bore diameter in the thrust

directions. (See step 4 on page

EM–143

)

(c) Subtract the piston diameter measurement from the

cylinder bore diameter measurement.

Standard oil clearance: 0.020–0.040 mm

(0.0008–0.0016 in.)

Maximum oil clearance: 0.06 mm (0.0024 in.)

If the oil clearance is greater than maximum, replace all the
eight pistons. If necessary, replace the cylinder block.
HINT (Use new cylinder block):

•

Use a piston with the same size mark as the cylinder
bore diameter size mark on the cylinder block.

•

The shape of the piston varies for the RH and LH banks.
The RH piston is marked with ”R”, the LH piston with ”L”.

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ENGINE MECHANICAL

Cylinder Block

EM–147

B.

Inspect piston ring groove clearance
Using a feeler gauge, measure the clearance between new
piston ring and the wall of the piston ring groove.

Ring groove clearance:

No.1 0.020–0.060 mm (0.0008–0.0024 in.)

No.2 0.015–0.055 mm (0.0006–0.0022 in.)

If the clearance is greater than maximum, replace the piston.

C.

Inspect piston ring end gap
(a) Insert the piston ring into the cylinder bore.
(b) Using a piston, push the piston ring a little beyond the

bottom of the ring travel, 105 mm (4.13 in.) from the top
of the cylinder block.

(c) Using a feeler gauge, measure the ring end gap.

Standard ring end gap:

No.1 0.250–0.450 mm

(0.0098–0.0177 in.)

No.2 0.350–0.600 mm

(0.0138–0.0236 in.)

Oil (Side rail) 0.150–0.500 mm

(0.0059–0.0197 in.)

Maximum ring end gap:

No.1 1.05 mm (0.0413 in.)

No.2 1.20 mm (0.0472 in.)

Oil (Side rail) 1.10 mm (0.0433 in.)

If the end gap is greater than maximum, replace the piston
ring. If the end gap is greater than maximum, even with a new
piston ring, replace the cylinder block.

D.

Inspect piston pin fit
At 60

°

C (140

°

F), you should be able to push the piston pin

into the piston pin hole with your thumb.

EM–148

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ENGINE MECHANICAL

Cylinder Block

3.

INSPECT CONNECTING ROD

A.

Inspect connecting rod alignment
Using a feeler gauge and rod aligner, check the connecting
rod alignment.

•

Check for bending.

Maximum bending:

0.05 mm (0.0020 in.) per 100 mm (3.94 in.)

If bent is greater than maximum, replace the connecting rod
assembly.

•

Check for twist.

Maximum twist:

0.15 mm (0.0059 in.) per 100 mm (3.94 in.)

If twist is greater than maximum, replace the connecting rod
assembly.

B.

Inspect connecting rod bushings
(a) Using a caliper gauge, measure the inside diameter of

the connecting rod bushing.

Bushing inside diameter: 22.005–22.017 mm

(0.8663–0.8668 in.)

(b) Using a micrometer, measure the piston pin diameter.

Piston pin diameter: 21.997–22.009 mm

(0.8660–0.8665 in.)

(c) Subtract the piston pin diameter measurement from the

bushing inside diameter measurement.

Standard oil clearance: 0.005–0.011 mm

(0.0002–0.0004 in.)

Maximum oil clearance: 0.05 mm (0.0020 in.)

C.

If necessary, replace connecting rod bushings
(a) Using SST and a press, press out the bushing.
SST 09222–30010

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ENGINE MECHANICAL

Cylinder Block

EM–149