Isuzu G150 Specifications
| Engine Model: Isuzu G150 |
| Engine Type: 4-stroke in-line 4-cylinder 8-valve OHV liquid-cooled gasoline |
| Total Displacement: 89.8 cu.in (1.47 L) |
| Rated Engine Power: 63-77 Hp (46-57 kW) at 5400 rpm |
| Fuel System Type: Carburetor |
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The Isuzu G150 is a 1.5-liter inline 4-cylinder
petrol engine from the early Isuzu G family. Introduced in the early
1960s, it represented one of Isuzu's first home-grown petrol designs
following the company's establishment as an independent manufacturer.
This engine served as a mainstay for Isuzu's compact passenger cars and
light commercial vehicles throughout the 1960s and early 1970s. The G150
was offered in multiple configurations, ranging from standard economy
variants to high-performance GT versions featuring twin carburetors and
increased compression ratios.
The Isuzu G150 represents a robust overhead valve petrol architecture
from the pre-emission control era, prioritizing mechanical simplicity
and serviceability. Its cast iron cylinder block with an overhead valve
(OHV) valvetrain provides a durable foundation suitable for passenger
car and light commercial applications. The engine underwent significant
evolution during its production life, with early variants utilizing a
three-main-bearing crankshaft design.
Later iterations received an upgraded five-main-bearing configuration
for improved crankshaft support and longevity at higher engine speeds.
The OHV valvetrain with eight valves offers straightforward access for
valve lash adjustment, a required maintenance item at regular intervals.
The carbureted fuel system, ranging from single downdraft units to twin
SU carburetors on GT variants, delivers fuel without electronic
complexity. The firing order of 1-3-4-2 provides balanced power impulses
across the crankshaft.
Engine Type: Inline 4-cylinder, 4-cycle, water-cooled, gasoline.
Displacement: 1,471 cc (89.8 cu.in).
Bore x Stroke: 79.0 mm x 75.0 mm (3.11 in x 2.95 in).
Compression Ratio (Standard): 7.5:1.
Compression Ratio (GT/Sport Variants): 8.0:1 to 8.5:1.
Firing Order: 1-3-4-2.
Maximum Power (Standard): 46-52 kW (63-70 hp) @ 5,000-5,400 rpm
Maximum Power (GT/Sport): 57 kW (77 hp) @ 5,400 rpm.
Maximum Torque (Standard): 110-115 Nm (81-85 lb-ft) @ 1,800-4,200 rpm.
Maximum Torque (GT/Sport): 120 Nm (89 lb-ft) @ 4,200 rpm.
Idle Speed (Warmed Up): 600 ± 50 rpm.
Valvetrain: OHV, 8 valves (2 per cylinder). Mechanical pushrods and
rocker arms.
The cylinder block is constructed from cast iron with a deep-skirt
design, providing structural rigidity for sustained operation. Early
production variants utilize a three-main-bearing crankshaft support
system. Later iterations incorporate an upgraded five-main-bearing
design, providing additional crankshaft support and reduced bearing
loads at higher engine speeds.
The cylinder bores are machined directly into the cast iron without
replaceable liners. The water jacket surrounds the cylinders with
cast-in coolant passages. The camshaft is located within the cylinder
block on the right-hand side, driven by a gear train from the
crankshaft. The engine mounting points are integrated into the block
casting on the front and sides.
The cylinder head is manufactured from cast iron, featuring an OHV
configuration with the camshaft located within the cylinder block. The
eight valves are arranged with two valves per cylinder positioned in a
vertical orientation. Valve actuation is achieved via mechanical
pushrods operating from the camshaft, with rocker arms transferring
motion to the valves.
Valve lash adjustment requires screw-and-locknut setting at the rocker
arms. The combustion chambers are of the wedge or bath-tub design,
depending on the compression ratio variant. Higher compression GT
variants utilize modified combustion chamber geometry and domed pistons
to achieve increased compression ratios. The cylinder head incorporates
separate intake and exhaust ports on opposite sides. Valve seats are
induction-hardened for wear resistance.
The fuel system utilizes carburetion, varying by engine variant.
Standard G150 engines employ a single downdraft carburetor, manufactured
by Hitachi or Nikki depending on production date. GT and sport variants
utilize twin side-draft SU carburetors for increased airflow and
improved throttle response.
A mechanical fuel pump, mounted to the cylinder block and driven by an
eccentric lobe on the camshaft, draws fuel from the tank and delivers it
to the carburetor float chamber. The intake manifold is constructed from
cast iron or aluminum depending on the carburetor configuration, with
single-carburetor intake manifolds for standard variants and
dual-carburetor intake manifolds with balanced runners for GT versions.
The lubrication system is a pressurized, wet-sump configuration. A
gear-type oil pump, driven by the camshaft or crankshaft depending on
production variant, circulates engine oil through a full-flow disposable
filter or a cleanable mesh filter element on early models.
Oil galleries within the block and cylinder head supply pressurized oil
to the crankshaft main bearings, connecting rod bearings, camshaft
bearings, and rocker arm assemblies. A pressure relief valve maintains
system pressure within specified limits. The oil sump is constructed
from pressed steel. Total oil capacity, including the filter, is 3.5-4.0
liters (3.7-4.2 qt), varying by oil pan configuration.
The cooling system is a pressurized, water-cooled design. A belt-driven
centrifugal water pump, mounted to the front of the cylinder block,
circulates coolant through the cylinder block, cylinder head, and
radiator. A wax-type or bellows-type thermostat, beginning to open at
76-82°C (169-180°F), regulates coolant flow to maintain optimal
operating temperatures.
The system utilizes a cross-flow or down-flow radiator depending on the
vehicle application, with a mechanical cooling fan driven by the water
pump pulley. Coolant capacity varies by vehicle application and radiator
size.
Ignition System: The G150 utilizes a distributor-based ignition system.
The distributor is driven by the camshaft or a separate drive gear from
the cylinder block. The system incorporates mechanical centrifugal
advance weights and a vacuum advance unit to adjust ignition timing
based on engine speed and load. Contact breaker points require periodic
adjustment and replacement. Ignition Timing (Standard): 12°-14° before
top dead center (BTDC) at idle with vacuum advance disconnected, varying
by specific model year and market.
Timing System: The camshaft and distributor are driven by a gear train
from the crankshaft. The crankshaft gear drives a camshaft gear directly
or through an intermediate idler gear. This gear-driven arrangement
eliminates timing belt or chain replacement requirements.
Emission Control: The engine incorporates a positive crankcase
ventilation (PCV) system on later variants. No catalytic converter or
exhaust gas recirculation system is present, reflecting the pre-emission
era of production.
Electrical System: The charging system consists of a 12-volt, 30-40 amp
generator (dynamo) on early variants or an alternator on later
production. The starter motor is a 0.8-1.0 kW (1.1-1.3 hp) unit.
Dry Weight (Three-Main-Bearing): 135 kg (298 lb).
Dry Weight (Five-Main-Bearing): 145 kg (320 lb).
Overall Length (from front pulley to flywheel housing): 710 mm (28.0
in).
Overall Width: 560 mm (22.0 in).
Overall Height: 690 mm (27.2 in).
Engine Oil Capacity (with filter): 3.5-4.0 liters (3.7-4.2 qt).
Engine Oil Specification: SAE 20W-50 or 15W-40 meeting API SE, SF, or
higher.
Engine Oil Pressure (at idle): Minimum 0.7 bar (10 psi) when warm.
Engine Oil Pressure (at 3,000 rpm): 2.5-3.5 bar (36-51 psi).
Coolant Capacity: 5.0-6.0 liters (5.3-6.3 qt), varying by radiator
configuration.
Coolant Specification: Ethylene glycol-based antifreeze with corrosion
inhibitors.
Intake Valve Clearance (Cold): 0.20-0.25 mm (0.008-0.010 in).
Exhaust Valve Clearance (Cold): 0.25-0.30 mm (0.010-0.012 in).
Valve Clearance Inspection Interval: Every 5,000 km (3,000 miles).
Spark Plug Type: NGK B6ES or equivalent.
Spark Plug Gap: 0.7-0.8 mm (0.028-0.031 in).
Spark Plug Replacement Interval: Every 10,000 km (6,000 miles).
Ignition Timing: 12°-14° BTDC @ 600 rpm with vacuum advance
disconnected.
Contact Breaker Point Gap: 0.40-0.50 mm (0.016-0.020 in).
Idle Speed: 600 ± 50 rpm.
Idle Mixture Adjustment: Set for maximum vacuum or smooth idle.
Carburetor Float Level: 22-25 mm (0.87-0.98 in) measured from gasket
surface.
Compression Pressure: Standard: 10.0-12.0 bar (145-174 psi) at cranking
speed.
Compression Pressure: Minimum allowable: 8.0 bar (116 psi).
Compression Pressure: Maximum variation between cylinders: 1.5 bar (22
psi).
Cylinder Head Bolts (M12), Stage 1: 30 Nm (22 lb-ft).
Cylinder Head Bolts (M12), Stage 2: 50 Nm (37 lb-ft).
Cylinder Head Bolts (M12), Stage 3: 70-75 Nm (52-55 lb-ft)
Main Bearing Cap Bolts (Three-Main-Bearing): 60-65 Nm (44-48 lb-ft)
Main Bearing Cap Bolts (Five-Main-Bearing): 70-75 Nm (52-55 lb-ft)
Connecting Rod Cap Nuts (M10): 40-45 Nm (30-33 lb-ft)
Camshaft Thrust Plate Bolts: 15-18 Nm (11-13 lb-ft)
Camshaft Gear Bolt: 50-55 Nm (37-41 lb-ft)
Flywheel Bolts: 55-60 Nm (41-44 lb-ft)
Crankshaft Pulley Bolt: 80-90 Nm (59-66 lb-ft)
Intake Manifold Nuts: 15-20 Nm (11-15 lb-ft)
Exhaust Manifold Nuts: 20-25 Nm (15-18 lb-ft)
Spark Plugs: 20-25 Nm (15-18 lb-ft)
Rocker Arm Shaft Bracket Bolts: 20-25 Nm (15-18 lb-ft)
Valve Cover Bolts: 5-7 Nm (4-5 lb-ft)
Oil Pan Bolts (M8): 8-10 Nm (6-7 lb-ft)
Oil Pump Mounting Bolts: 15-18 Nm (11-13 lb-ft)
Water Pump Mounting Bolts: 15-18 Nm (11-13 lb-ft)
Carburetor Mounting Nuts: 10-12 Nm (7-9 lb-ft)
Engine Mount (Bracket to Block): 35-40 Nm (26-30 lb-ft)
The Isuzu G150 engine was utilized across several Isuzu passenger car
and light commercial vehicle platforms during its production lifecycle.
Isuzu Bellett (1963-1973): The primary application for the G150 engine,
including the Bellett 1500 sedan, delivered in standard
single-carburetor configuration. The Bellett 1500 GT variant received
the higher-output twin-carburetor G150 engine producing 57 kW (77 PS).
Isuzu Wasp (KR20): A rare 1-ton pickup variant marketed in select export
markets, notably Australia, utilizing the single-carburetor G150 engine
for light commercial duty.
Isuzu Elf (TL/KA Series): Early light-duty versions of the Elf
commercial truck received the G150 engine in low-compression 7.5:1
configuration for improved durability under sustained load.
Isuzu Bellel: The Bellel sedan, Isuzu's first home-designed passenger
car, received the G150 engine in 1.5-liter petrol variants during early
production years before the introduction of larger-displacement engines.
Isuzu Florian: Early Florian variants in certain Asian markets utilized
the G150 engine as a base powerplant option before the transition to the
larger G160 and G180 engines.
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