Isuzu KB P190. Manual - part 625

Engine Mechanical – V6 

Page 6A1–21 

 

1.4 Engine 

Construction 

Cylinder Block 

The cylinder block (1) is constructed from aluminium alloy 
with cast-in-place iron cylinder bore liners.  

Each of the four copper-infiltrated sintered steel main 
bearing caps are attached to the cylinder block by six bolts. 
Along with two outer and two inner bolts, two side bolts are 
used in the deep skirt block for increased block stiffness. 

The crankshaft thrust bearing is mounted in the third main 
bearing cap.  

To prevent aeration, oil return from the valve train and 
cylinder heads is channelled away from the reciprocating 
components through oil drain back passages incorporated 
into the cylinder heads and engine block. Pressure 
actuated piston oil cooling jets are mounted between 
opposing cylinders. 

Figure 6A1 – 14 

Cylinder Heads 

The cylinder heads (1) are semi-permanent mould cast 
aluminium with powdered metal valve seat inserts and 
valve guides. 

Figure 6A1 – 15 

Each cylinder head contains four valves per cylinder. The 
valves (1) are actuated by the rocker arms (2) that pivot on 
stationary hydraulic lash adjusters (3), which are oil-fed to 
maintain valve / rocker lash. 

 

The separate exhaust and intake camshafts are supported 
by four bearings machined into the cylinder head. The front 
camshaft bearing cap is used as a thrust control surface for 
each camshaft. 

 

A tube (4) is pressed into each cylinder head in three 
places that shields each spark plug. An ignition coil 
assembly is mounted directly on each spark plug, through 
each spark plug tube. 

Figure 6A1 – 16 

Engine Mechanical – V6 

Page 6A1–22 

 

Crankshaft 

The crankshaft is a forged steel design with four main bearings. The number three main bearing controls crankshaft 
thrust. A crankshaft position reluctor wheel is pressed onto the rear of the crankshaft, in front of the rear main journal. 
The crankshaft is internally balanced with an integral oil pump drive machined into the nose in front of the front main 
journal. 

Pistons, Pins and Connecting Rods 

The piston assembly (1) is fitted with two low tension 
compression rings and one multi-piece oil control ring. The 
top compression ring is plasma sprayed, while the second 
compression ring is cast iron Napier.  

The oil control ring incorporates a steel expander and two 
chrome plated steel rails. 

The connecting rods are sinter forged steel and have full 
floating piston pins. The piston pins are a slip-fit type, into 
the bronze bushed connecting rods. Round wire retainers 
are used to retain the piston pin into the piston.  

The cast aluminium pistons incorporate a polymer coated 
skirt to reduce friction.  

Figure 6A1 – 17 

Camshaft Drive System 

Three timing chains are fitted: 
• 

primary (1), 

• 

right-hand secondary (2), and 

• 

left-hand secondary (3), refer to Figure 6A1 – 18 for the HFV6 engine. 

The primary timing chain connects the crankshaft sprocket (4) with the left-hand and right-hand intermediate drive shaft 
sprockets (5). 

Each oil pressure fed intermediate sprocket drives the secondary timing chains, which subsequently drive the respective 
cylinder head camshaft position actuators (6). 

Two stationary timing chain guides (7) and movable timing chain shoes (8) control secondary timing chain backlash.  

Each secondary timing chain shoe is under tension from an oil pressure hydraulically operated tensioner (9). To control 
backlash on the primary chain, two stationary timing chain guides (10) and an oil pressure hydraulically actuated 
tensioner with built in shoe (11) are fitted. 

The tensioners minimise timing chain noise and provide accurate valve action by keeping slack out of the timing chains, 
while continuously adjusting for timing chain wear. The tensioners incorporate a plunger that adjusts outward with wear, 
minimising backlash. The tensioners are equipped with oiling jets to spray oil onto the timing components during engine 
operation. Each tensioner is sealed to the head or block using a rubber coated steel gasket. The gasket traps an 
adequate oil reserve to ensure quiet start-up. 

Engine Mechanical – V6 

Page 6A1–23 

 

 

Figure 6A1 – 18 

Legend 

1 

Primary Timing Chain 

2 

Secondary Timing Chain, Right-hand 

3 

Secondary Timing Chain, Left-hand 

4 Crankshaft 

Sprocket 

5 

Intermediate Driveshaft Sprocket 

6 Camshaft 

Sprocket 

7 

Secondary Timing Chain Guide  

8 

Secondary Timing Chain Shoe 

9 

Secondary Timing Chain Tensioner 

10 

Primary Timing Chain Guide 

11 

Primary Timing Chain Tensioner 

 

Engine Mechanical – V6 

Page 6A1–24 

 

1.5 

Engine Lubrication System 

Lubrication Description 

A structural diecast aluminium oil pan is fitted that incorporates an oil suction pipe, an oil deflector and an oil level sensor. 
The oil suction pipe is bolted into the oil pan and seals to the bottom of the cylinder block with a gasket. The oil deflector 
is bolted to the upper portion of the oil pan and ensures oil supply is maintained under all conditions. The oil level sensor 
is mounted through the bottom of the oil pan. 

A crankshaft driven gerotor oil pump is mounted to the front of the cylinder block. The pump, which incorporates an 
internal pressure-relief valve, draws oil from the oil suction tube through the lower passage in the cylinder block. Oil is 
then directed through an upper passage to the left-hand side of the cylinder block where the oil filter adapter is mounted. 

The oil filter adapter incorporates a top-access, cartridge style oil filter. The filter is accessed through a screw-on cap that 
incorporates an oil bypass valve. The oil filter adapter housing incorporates a drain back control valve and a threaded oil 
pressure sender. Oil flows through a lower passage within the oil filter adapter and through the oil filter cartridge. Filtered 
oil travels back through the upper passage of the adapter and into the engine block. 

Oil is then directed up and across the front of the cylinder block, through several drilled passages. These front passages 
feed oil to each cylinder head, the passage for the main bearings and piston oil jets, the right-hand and left-hand 
secondary idler sprockets and to the primary timing chain tensioner. 

Each cylinder head passage directs oil into oiling circuits for the stationary hydraulic lash adjusters (SHLAs) and the 
camshaft bearing journals.  An additional passage in the cylinder head also directs oil to the secondary timing chain 
tensioner. 

The oil passage that supplies oil to the main bearings also supplies oil to pressure actuated piston cooling oil jets. Each 
oil jet is mounted between opposing cylinder bores and directs oil to the two bores to provide extra cooling and control 
piston temperatures. 

From the front passages, oil is directed to the front of the block where the right-hand and left-hand intermediate drive 
shaft sprockets and the primary timing chain tensioner are mounted. Each camshaft timing chain tensioner relies on a 
gasket to maintain an oil reserve after the engine is turned off. All camshaft timing chain tensioners incorporate a small 
oil jet to supply an oil spray onto the camshaft timing chain components. 

Oil returns to the oil pan, either through the camshaft timing chain area or through the drain back passages on the 
outboard walls of the cylinder heads and cylinder block. 

1.6 Service 

Notes 

Cleanliness and Care 

Throughout this Section, correct cleaning and protection of machined surfaces and friction areas is a part of the repair 
procedure. This is considered standard workshop practice, even if not specifically stated. 

When any internal engine part is serviced, care and cleanliness is extremely important. 

When components are removed for service, they should be marked, organised or retained in a specific order for 
reassembly. 

At the time of installation, components should be installed in the same location and with the same mating surface as 
when removed. 

Any engine is a combination of many machined, honed, polished and lapped surfaces with tolerances that are measured 
in thousandths of a millimetre. These surfaces should be covered or protected to avoid component damage. 

A liberal coating of clean engine oil should be applied to friction areas during assembly, as the lubrication will protect and 
lubricate friction surfaces during the initial engine start-up. 

Replacing Engine Gaskets 

Re-Using Gaskets and Applying Sealants 

• 

do not reuse any gasket unless specified, 

• 

gaskets that can be reused will be identified in the service procedure, and 

• 

do not apply sealant to any gasket or sealing surface unless specified in the service information. 

Separating Components 

• 

Use a rubber mallet to separate components. 

• 

Bump the part sideways to loosen the components. 

• 

Bumping should be done at bends or reinforced areas to prevent distortion of parts. 

Cleaning Gasket Surfaces 

• 

Where required, remove all gasket and sealing material from the part using a plastic or wood scraper. 

• 

Care must be used to avoid gouging or scraping the sealing surfaces.