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Isuzu 4BC2 Engine

The Isuzu 4BC2 is a 3.3-liter (3,268 cc) inline 4-cylinder, four-stroke, water-cooled naturally aspirated diesel engine. Produced primarily throughout the 1980s, this engine was heavily utilized in light-duty commercial vehicles and pickup trucks, including the Isuzu Elf series (KT26, TLD57, NKR57, NPR57). Constructed with a heavy-duty cast iron cylinder block and head, the 4BC2 is engineered as a high-durability power plant optimized for reliable torque delivery, low-maintenance operations, and long service life under heavy load cycles.

Valvetrain Configuration: The engine utilizes an Overhead Valve (OHV) pushrod layout powered by a gear-driven camshaft within the cylinder block. It features 2 valves per cylinder (8 valves total). The nominal power rating is 88.7 Hp (66 kW) achieved at a maximum governed speed of 3,500 RPM. Peak torque delivery is rated at 200 Nm (148 lb-ft) at 2,000 RPM. Bore and Stroke: The cylinder bore diameter measures 102 mm, paired with a piston stroke of 100 mm.

Fuel System: The system uses a mechanical, inline Bosch-type injection pump that synchronizes fuel delivery directly to the cylinders. It relies on a mechanical compression-ignition design operating via a firing order of 1-3-4-2. The fuel architecture features pre-filters and water separators to protect high-pressure components from contamination.

Forced lubrication loop distributed by a trochoid-type oil pump driven off the gear train. The system incorporates a full-flow replaceable spin-on oil filter element alongside an integrated oil cooler assembly bypass circuit to stabilize oil temperatures during prolonged high-load cycles. Cooling System: Liquid-cooled, closed-loop system featuring a belt-driven water pump, a heavy-duty radiator, and a multi-blade cooling fan. Thermal regulation is maintained via a conventional pellet-type thermostat housed in the water outlet pipe to manage proper warmup and operational ranges.

General Technical Data

Engine Specifications

Engine Model ............... Isuzu 4BC2
Engine Type ............... 4-cycle inline 4-cylinder direct injection liquid-cooled diesel
Number of Cylinders ............... 4
Cylinder Arrangement ............... In-line
Engine Bore, in (mm) ............... 4.02 (102.0)
Engine Stroke, in (mm) ............... 3.94 (100.0)
Displacement, cu.in (L) ............... 199.4 (3.268)
Rated Engine Power, hp (kW) ............... 88.7 (66.0)
Rated Engine Speed, rpm ............... 3500
Peak Torque ............... 200 Nm (148 lb-ft) at 2000 rpm
Idle Speed, rpm ............... 750-850
Aspiration Type ............... Naturally Aspirated
Operating Speed, rpm ............... 2000-3500
Compression Ratio ............... 17.0:1-17.5:1
Firing Order ............... 1-3-4-2
Valvetrain Type ............... Overhead Valve gear driven pushrod
Number of Valves per Cylinder ............... 2
Total Number of Valves ............... 8
Cylinder Block Type ............... Cast iron
Cylinder Head Type ............... Cast iron
Lubrication System ............... Full-pressure
Oil Pump Type ............... Gear-driven
Oil Filter Type ............... Full-flow, spin-on
Cooling System ............... Liquid-cooled
Water Pump Type ............... Belt-driven, centrifugal
Air Cleaner Type ............... Dry dual-stage
Starting System ............... Electric Starter
Electrical System, V ............... 12 or 24
Alternator Capacity, A ............... 35-50

Fuel System

Injection Pump Type ............... Bosch In-line A-Type
Governor Type ............... Mechanical RSV or RLD
Feed Pump Type ............... Piston type plunger pump
Injection Nozzle Type ............... Multi-hole type nozzle
Number of Nozzle Holes ............... 4
Nozzle Hole Diameter, in (mm) ............... 0.0102 (0.26)
Injection Start Pressure, psi (bar) ............... 2556-2698 (176.2-186.0)
Fuel Filter Type ............... Spin-on cartridge element
Fuel Delivery Pressure, psi (bar) ............... 22-36 (1.5-2.5)
Maximum Fuel System Backpressure, in Hg (kPa) ............... 3.94 (13.3)
Fuel Injection Timing, deg BTDC ............... 12-14
Pre-heating System Type ............... Glow plugs
Glow Plug Voltage, V ............... 12 or 24
Glow Plug Resistance, Ohms ............... 0.5-0.9
Over-flow Valve Opening Pressure, psi (bar) ............... 20-23 (1.4-1.6)

Dimensions and Weight

Overall Length, in (mm) ............... 31.5 (800)
Overall Width, in (mm) ............... 20.8 (530)
Overall Height, in (mm) ............... 19.4 (495)
Dry Weight, lbs (kg) ............... 492 (223)
Wet Weight, lbs (kg) ............... 525 (238)

Maintenance Data

Service Information

Compression Pressure at 200 rpm, psi (bar) ............... 441 (30.4)
Compression Pressure, Minimum Limit, psi (bar) ............... 327 (22.5)
Maximum Pressure Between Cylinders, psi (bar) ............... 28.4 (1.96)
Minimum Oil Pressure at Idle, psi (bar) ............... 14.2 (0.98)
Normal Operating Oil Pressure, psi (bar) ............... 42.7-56.9 (2.94-3.92)
Thermostat Opening Temperature, F (C) ............... 170.6 (77.0)
Thermostat Fully Open Temperature, F (C) ............... 194.0 (90.0)
Radiator Cap Relief Pressure, psi (bar) ............... 12.8 (0.88)
Intake Valve Clearance (Cold), in (mm) ............... 0.0157 (0.40)
Exhaust Valve Clearance (Cold), in (mm) ............... 0.0157 (0.40)

Engine Oil and Coolant

Engine Oil Type .................. SAE 10W-30, or SAE 15W-40
API Service Classifications ......................... CD, CE, or CF-4
Engine Oil Capacity with Filter, qt (L) ............... 7.93 (7.5)
Engine Oil Capacity without Filter, qt (L) ............... 7.19 (6.8)
Cooling System Fluid Capacity, qt (L) ............... 10.57 (10.0)

Service Intervals

Change oil and filter ............... Every 250 hours
Inspect air cleaner ............... Every 100 hours
Replace air cleaner ............... Every 500 hours
Replace fuel filter ............... Every 500 hours
Valve clearance adjustment ............... Every 1000 hours
Fuel system inspection ............... Every 1000 hours
Change coolant ............... Every 2000 hours
Compression test ............... Every 1000 hours
Belt inspection ............... Every service cycle

Service Specifications

Cylinder Bore Diameter, in (mm) ............... 4.0165-4.0181 (102.020-102.060)
Cylinder Bore Out-of-Round, Limit, in (mm) ............... 0.0008 (0.020)
Cylinder Bore Taper, Limit, in (mm) ............... 0.0008 (0.020)
Cylinder Block Upper Face Flatness, in (mm) ............... 0.0020 (0.050)
Cylinder Head Lower Face Flatness, in (mm) ............... 0.0020 (0.050)
Crankshaft End Play, in (mm) ............... 0.0031-0.0071 (0.080-0.180)
Crankshaft Run-out, Limit, in (mm) ............... 0.0012 (0.030)
Main Journal Outer Diameter, in (mm) ............... 2.9887-2.9892 (75.913-75.925)
Main Bearing Clearance, in (mm) ............... 0.0015-0.0031 (0.039-0.080)
Connecting Rod Journal Outer Diameter, in (mm) ............... 2.5556-2.5561 (64.913-64.925)
Connecting Rod Bearing Clearance, in (mm) ............... 0.0014-0.0028 (0.035-0.072)
Connecting Rod Side Clearance, in (mm) ............... 0.0067-0.0118 (0.170-0.300)
Piston Outer Diameter Standard, in (mm) ............... 4.0124-4.0138 (101.915-101.950)
Piston to Cylinder Wall Clearance, Std, in (mm) ............... 0.0031-0.0047 (0.080-0.120)
Piston to Cylinder Wall Clearance, Limit, in (mm) ............... 0.0079 (0.200)
Piston Pin Outer Diameter, in (mm) ............... 1.3382-1.3386 (33.990-34.000)
Piston Pin Small End Bushing I.D, in (mm) ............... 1.3390-1.3396 (34.010-34.025)
Piston Pin to Bushing Clearance, in (mm) ............... 0.0004-0.0014 (0.010-0.035)
Top Ring Groove Width, in (mm) ............... 0.0961-0.0969 (2.440-2.460)
Second Ring Groove Width, in (mm) ............... 0.0799-0.0807 (2.030-2.050)
Oil Ring Groove Width, in (mm) ............... 0.1783-0.1791 (4.530-4.550)
Top Ring Side Clearance, in (mm) ............... 0.0024-0.0039 (0.060-0.100)
Second Ring Side Clearance, in (mm) ............... 0.0020-0.0035 (0.050-0.090)
Oil Ring Side Clearance, in (mm) ............... 0.0012-0.0028 (0.030-0.070)
Top Ring End Gap, in (mm) ............... 0.0098-0.0157 (0.250-0.400)
Second Ring End Gap, in (mm) ............... 0.0079-0.0138 (0.200-0.350)
Oil Ring End Gap, in (mm) ............... 0.0079-0.0157 (0.200-0.400)
Intake Valve Stem Outer Diameter, in (mm) ............... 0.3524-0.3531 (8.950-8.970)
Exhaust Valve Stem Outer Diameter, in (mm) ............... 0.3512-0.3520 (8.920-8.940)
Intake Valve Guide Inner Diameter, in (mm) ............... 0.3543-0.3551 (9.000-9.020)
Exhaust Valve Guide Inner Diameter, in (mm) ............... 0.3543-0.3551 (9.000-9.020)
Intake Valve Guide to Stem Clearance, in (mm) ............... 0.0012-0.0028 (0.030-0.070)
Exhaust Valve Guide to Stem Clearance, in (mm) ............... 0.0024-0.0039 (0.060-0.100)
Valve Thickness, Standard, in (mm) ............... 0.0669 (1.70)
Valve Thickness, Limit, in (mm) ............... 0.0472 (1.20)
Valve Spring Free Length, Standard, in (mm) ............... 1.8898 (48.00)
Valve Spring Free Length, Limit, in (mm) ............... 1.8110 (46.00)
Camshaft Journal Outer Diameter, in (mm) ............... 2.2024-2.2035 (55.940-55.970)
Camshaft Bearing Inner Diameter, in (mm) ............... 2.2047-2.2076 (56.000-56.073)
Camshaft Journal Clearance, in (mm) ............... 0.0012-0.0035 (0.030-0.090)
Camshaft Run-out, Limit, in (mm) ............... 0.0039 (0.100)
Cam Height, Standard, in (mm) ............... 1.8780 (47.700)
Cam Height, Limit, in (mm) ............... 1.8307 (46.500)
Tappet Body Outer Diameter, in (mm) ............... 1.1003-1.1010 (27.947-27.965)
Tappet to Block Clearance, in (mm) ............... 0.0008-0.0021 (0.020-0.054)
Rocker Arm Shaft Run-Out, Limit, in (mm) ............... 0.0118 (0.300)
Rocker Arm Shaft Outer Diameter, in (mm) ............... 0.7472-0.7480 (18.980-19.000)
Rocker Arm Bushing Inner Diameter, in (mm) ............... 0.7484-0.7492 (19.010-19.030)
Rocker Arm to Shaft Clearance, in (mm) ............... 0.0004-0.0020 (0.010-0.050)

Tightening Torques

Cylinder Head Bolt, Stage 1, lb-ft (Nm) ............... 37 (50)
Cylinder Head Bolt, Stage 2, lb-ft (Nm) ............... 48 (65)
Cylinder Head Bolt, Stage 3, deg ............... 87 (120)
Main Bearing Cap Bolt, lb-ft (Nm) ............... 177 (240)
Connecting Rod Cap Bolt, lb-ft (Nm) ............... 88 (120)
Flywheel Bolt, lb-ft (Nm) ............... 118 (160)
Crankshaft Damper Pulley Bolt, lb-ft (Nm) ............... 318 (431)
Camshaft Gear Bolt, lb-ft (Nm) ............... 81 (110)
Idler Gear Shaft Bolt, lb-ft (Nm) ............... 24 (32)
Rocker Arm Shaft Bracket Bolt, lb-ft (Nm) ............... 16 (22)
Valve Cover Nut, lb-ft (Nm) ............... 11 (15)
Oil Pan Drain Plug, lb-ft (Nm) ............... 61 (83)
Oil Pan Mounting Bolt, lb-ft (Nm) ............... 14 (19)
Exhaust Manifold Stud Nut, lb-ft (Nm) ............... 29 (39)
Intake Manifold Bolt, lb-ft (Nm) ............... 17 (23)
Injection Pump Drive Gear Nut, lb-ft (Nm) ............... 46 (62)
Injection Pump Mounting Bolt, lb-ft (Nm) ............... 17 (23)
Injection Nozzle Holder Gland Nut, lb-ft (Nm) ............... 27 (37)
Fuel Injection Pipe Flare Nut, lb-ft (Nm) ............... 22 (29)
Oil Pump Mounting Bolt, lb-ft (Nm) ............... 16 (22)
Water Pump Mounting Bolt, lb-ft (Nm) ............... 16 (22)
Thermostat Housing Bolt, lb-ft (Nm) ............... 16 (22)
Starter Motor Mounting Bolt, lb-ft (Nm) ............... 63 (85)
Alternator Mounting Bolt, lb-ft (Nm) ............... 33 (45)
Glow Plug Torque, lb-ft (Nm) ............... 18 (25)
Oil Filter Center Stud, lb-ft (Nm) ............... 22 (30)

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• Isuzu Engines Specs
  
• Isuzu 4BA1 Specs
  
• Isuzu 4BB1 Specs
  
• Isuzu 4BC1 Specs
  
• Isuzu 4BD1 Specs
  
• Isuzu 4BD1T Specs
  

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