Lexus RX300 (MCU15). Service manual - part 38

EG

ENGINE — 1MZ-FE ENGINE

25

JENGINE PROPER

1. Cylinder Head Cover

D Lightweight yet high-strength aluminum diecast cylinder head covers are used.

D In order to improve sealing, reduce noise, and prevent excessive tightening during service, an aluminum

washer made of vibration-damping laminated aluminum sheet is used on the evenly spaced shoulder
bolts which fasten the cylinder head covers.

187EG04

For Right Bank

For Left Bank

Engine
Front

Gasket

Cylinder
Head Cover

Rubber

Aluminum

Cylinder
Head Cover

A

A

A – A Cross Section

2. Cylinder Head Gasket

D A carbon graphite type cylinder head gasket which offers superior pressure resistance and sealing perfor-

mance has been adopted.

D The bore grommets are made of stainless steel to increase reliability and durability.

187EG05

For Right Bank

For Left Bank

Engine Front

ENGINE — 1MZ-FE ENGINE

26

3. Cylinder Head

D The cylinder head, which is made of aluminum, has adopted a pentroof-type combustion chamber.  The

spark plug has been located in the center of the combustion chamber in order to improve the engine’s
antiknocking performance.

D The angle of the intake and exhaust valves is narrowed and set at 22.5° to permit a compact cylinder

head.

D Upright, small-diameter intake ports are adopted to improve the torque at low-to-medium speeds.

D In order to reduce intake & exhaust air resistance, the cross section of the protrusion of the valve guide

into the intake port has been reduced by decreasing the valve stem diameter and the valve guide outer
diameter.

D Plastic region tightening bolt is used for the cylinder head bolts for good axial tension.

187EG07

187EG06

Valve Angle

22.5

°

EX

IN

Intake Valve

Spark Plug

Exhaust Valve

EG

ENGINE — 1MZ-FE ENGINE

27

4. Cylinder Block

D The cylinder block has a bank angle of 60°, a bank offset of 36.6 mm (1.44 in.) and a bore pitch of

105.5 mm (4.15 in.), resulting in a compact block.

D Lightweight aluminum alloy is used for the cylinder block.

D A thin cast-iron liner is press-fit inside the cylinder to ensure an added reliability.  This liner is thin,

so that boring is not possible.

D A water pump swirl chamber and an inlet passage to the pump are provided in the V-bank to help make

the engine compact.

D Knock sensor bosses are provided at 2 locations in the V-bank.

D The crankshaft bearing caps are tightened using 4 plastic-region bolts for each journal.  In addition,

each cap is tightened laterally to improve its reliability.

Plastic Region Tightening Bolts

187EG08

187EG09

187EG10

Water Pump Swirl Chamber

Knock Sensor Bosses

Top View

Crankshaft Bearing Cap

Seal Washer

105.5 mm

36.6 mm

60

°

ENGINE — 1MZ-FE ENGINE

Knock Pin

Plastic Region
Tightening
Bolt

187EG12

28

5. Piston

D The piston is made of aluminum alloy and skirt area is made compact and lightweight.

D Resin coating is applied to the piston skirt area and thin piston rings are used to reduce friction.

D Each of the pistons is made specifically for the right or left bank.

D Full floating type piston pins are used.

For Right Bank

For Left Bank

Engine
Front

187EG11

6. Connecting Rod

D Connecting rods that have been forged for high

strength are used for weight reduction.

D An aluminum bearing with overlay is used for the

connecting rod bearings to improve durability.

D Plastic region tightening bolts are used.

D Knock pins are used at the mating surfaces of the

bearing caps of the connecting rod to minimize
the shifting of the bearing caps during assembly.