Toyota 1HZ

Toyota 1HZThe Toyota 1HZ is a 4.20 l (4,164 cc, 254.1 cu-in) six cylinders, four-stroke cycle water-cooled naturally aspirated internal combustion diesel engine, manufactured by the Toyota Motor Corporation.

The 1HZ engine has a cast-iron cylinder block with 94.0 mm (3.7 in) cylinder bores and a 100.0 mm (3.94 in) piston stroke. Compression ratio rating was 22.7:1. In 1998, the 1HZ engine received a reinforced cylinder block and crankshaft, new pistons and glow plugs, the compression was reduced to 22.4:1. Since 2002 the engine is equipped with an EGR system.

The motor has a cast iron cylinder head with the single overhead camshaft (SOHC) with two valves per cylinder and indirect injection design.

The Toyota 1HZ produced 131 PS (96 kW; 129 HP) at 3,800 rpm or 135 PS (99 kW; 133 HP) at 4,000 rpm of maximum horsepower and 279 Nm (28.5 kg·m; 205.9 ft·lb) at 2,200 rpm or 284 Nm (29.0 kg·m; 209.6 ft·lb) at 2,200 rpm of maximun torque.

The breakdown of the engine code is as follows:

  • 1 – 1st generation engine
  • HZ – Engine family

General information

Engine Specifications
Engine code1HZ
LayoutStraight-6, vertical
Fuel typeDiesel
Production
Displacement4.2L, 4,164 cc (254.1 cu in)
Injection pumpMechanical
Power adderNone
Horsepower net 131 PS (96 KW; 129 HP) at 3,800 rpm
135 PS (99 KW; 133 HP) at 4,000 rpm
Torque output 279 Nm (28.5 kg·m; 205.9 ft·lb) at 2,200 rpm
284 Nm (29.0 kg·m; 209.6 ft·lb) at 2,200 rpm
Firing order1-4-2-6-3-5
Dimensions (L x H x W):
Weight

Cylinder block

The cylinder block is made of cast iron. The crankshaft is supported by 7 bearings on the inside of the crankcase. The crankshaft bearings are made of aluminum alloy. The crankshaft is integrated with 12 balance weights which are cast along with it for balance. Oil holes are built into the crankshaft for supplying oil to the connecting rods, bearings and etc. The crankshaft bearing cap is of ladder-frame construction and is incorporated into the crankcase.

Pistons are made of highly temperature-resistant aluminum alloy. The first compression ring is made of steel and the second compression ring is made of cast iron. The oil ring is made of steel.

The cylinder bore is 94 mm (3.7 in), piston stroke is 100 mm (3.94 in) and compression ratio rating is 22.7:1 or 22.4:1 (after 1998).

Cylinder block
Cylinder block alloyCast iron
Compression ratio:22.7:1 or 22.4:1
Cylinder bore:94 mm (3.7 in)
Piston stroke:100 mm (3.94 in)
Number of piston rings (compression / oil):2 / 1
Number of main bearings:7
Cylinder bore inner diameter:94.000-94.030 mm (3.7001-3.7019 in)
Piston skirt diameter 93.885-94.895 mm (3.6962-3.6966 in)
93.950-93.960 mm (3.6988-3.6992 in)
Piston ring groove:First0.050-0.095 mm (0.0020-0.0037 in)
Second0.060-0.100 mm (0.0024-0.0039 in)
Oil0.030-0.070 mm (0.0012-0.0028 in)
Piston ring end gap:First0.270-0.540 mm (0.0106-0.0212 in)
Second0.400-0.620 mm (0.0157-0.0244 in)
Oil0.200-0.520 mm (0.0079 – 0.0204 in)
Piston pin outer diameter 29.000-29.012 mm (1.1417-1.1412 in)
33.000-33.012 mm (1.2992-1.2997 in)
Piston pin bore diameter 29.008-29.020 mm (1.1420-1.1425 in)
33.008-33.020 mm (1.2995-1.3000 in)
Crankshaft main journal diameter:66.994-67.004 mm (2.6375-2.6379 in)
Crankpin diameter:58.994-59.004 mm (2.3225-2.3230 in)
Crankshaft center distance:50.0 mm (1.9685 in)

Main bearing cap tightening procedure and torque specs:

  • Step 1: 103 Nm; 10.5 kg·m; 76 ft·lb
  • Step 2: Turn all bolts 90°

After securing bearing cap bolts, make sure crankshaft turns smoothly by hand.

Connecting rod bearing nut

  • Step 1: 37 Nm; 3.75 kg·m; 27 ft·lb
  • Step 2: Turn all bolts 90°

Crankshaft pulley bolt

  • 500 Nm; 50.0 kg·m; 369 ft·lb

Flywheel (M/T) or Drive plate (A/T) fixing bolts

  • 127 Nm; 13.0 kg·m; 94 ft·lb

Cylinder head

The cylinder head is made of cast iron with a cross-flow type intake and exhaust layout. The combustion chambers are swirl chamber type. The camshaft journal part of the cylinder head has camshaft caps made of aluminum alloy and is made of cast iron on the cylinder head side. The camshaft is driven by the timing belt.

The 1HZ engine has OHV design with two valves per cylinder. Intake valves are 42.5 mm (1.6732 in) in diameter, and the exhaust valves are 36.0 mm (1.4173 in). Exhaust and intake valves are equipped with irregular pitch springs which are capable of following the valves even at high engine speeds. The 1HZ engine has a dual-type exhaust manifold.

Adjustment of the valve clearance is done by means of an outer shim type system, in which valve adjusting shims are located above the valve lifters.

Cylinder head
Cylinder head alloyCast iron
Valve Arrangement:SOHC
Valves:12 (2 valves per cylinder)
Intake valves diameter:42.5 mm (1.6732 in)
Exhaust valves diameter:36.0 mm (1.4173 in)
Intake valves length:103.29-103.69 mm (4.0665-4.0822 in)
Exhaust valves length:103.14-103.54 (4.0606-4.00764 in)
Intake valve stem diameter:7.975-7.990 mm (0.3140-0.3145 in)
Exhaust valves stem diameter:7.960-7.975 mm (0.3133-0.3140 in.l
Camshaft journal diameter: 1st: 34.969-34.985 mm (1.3767-1.3774 in)
Others: 27.986-27.998 mm (1.1018-1.1023 in)
Camshaft lobe height (intake):55.090-55.110 mm (2.1689-2.1697 in)
Camshaft lobe height (exhaust):55.940-55.960 mm (2.2024-2.2031 in)

Head tightening procedure and torque specs:

  • Step 1: 69 Nm; 7.0 kg·m; 51 ft·lb
  • Step 2: Turn all bolts 90°
  • Step 3: Turn all bolts 90°

Camshaft bearing cap

  • No.1 journal: 25 Nm; 2.5 kg·m; 18 ft·lb
  • Others: 18 Nm; 1.85 kg·m; 13 ft·lb

Maintenance data

Valve clearance (Cold)
Intake valve0.15-0.25 mm (0.006-0.0098 in)
Exhaust valve0.35-0.45 mm (0.0137-0.0177 in)
Compression pressure
Standard37.0 kg/m2 (3,628 kPa, 526 psi) / 250 rpm
Minimun27.0 kg/m2 (2,648 kPa, 384 psi) / 250 rpm
Compression differential limit between cylinders5.0 kg/m2 (490 kPa, 71 psi) / 250 rpm
Oil system
Recommended engine oil10W-30 or 10W-40 (“CC”, “CD” or higher: “CH”, “CI”)
Engine oil capacity Dry fill: 9.6 L (10.1 US qt, 8.4 Imp. qt)
With oil filter change: 9.3 L (9.8 US qt, 8.1 Imp. qt)
Without oil filter change: 8.0 L (8.5 US qt, 7.0 Imp. qt)
Fuel system
Plunger stroke:1.03-1.09 mm (0.0406-0.0429 in.)
Idling M/T: 650 ± 50 rpm
A/T: 700 ± 50 rpm

Vehicle applications

ModelYears Produced
Toyota Land Cruiser (J75, J78, J79)
Toyota Land Cruiser (HZJ77)
Toyota Land Cruiser (J80)
Toyota Land Cruiser (J105)
Toyota Coaster (HZB30, HZB40)
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14 Comments

  1. Is the 14mm hexagon head cylinder head bolt torque specification ( 69Nm;7.0kg•m;51ft/lb),the same as in 12mm hexagon head cylinder head bolt torque specification?

  2. I’m after the weight of a bare 1HZ diesel cast block. It doesn’t have any crank, bearings, heads or anything fitted, just the bare cast block.

  3. I am considering turbo conversion with inter cooler, set up on dyno tune, Cruiser is 1993 huh 75, traveled 350,000 km approx, don’t want the expense of upgrading pistons or crank, what are your thoughts or experiences, thanks for your replies in advance, regards Cliff

  4. I’m interested to know whether there are retrofit devices (DPF & / or SCR) available that would make my 1HZ engine Euro 4 compliant

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