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Isuzu 3CB1 Engine

The Isuzu 3CB1 is a heavy-duty, industrial-grade 3-cylinder, 4-cycle diesel engine engineered primarily for stationary power generation, agricultural machinery, and industrial drive applications. Manufactured by Isuzu Motors in Japan, it belongs to the high-performance 3C-Series engine family.
Designed as a vertical, inline unit, this engine features a naturally aspirated air intake system combined with a rigid engine block structure. Its engineering design focuses on delivering high torque rise at lower engine speeds, minimizing combustion noise, reducing maintenance demands, and meeting stringent emissions compliance protocols. The compact architectural layout incorporates integrated mounting points to withstand heavy industrial duty cycles.

The valve mechanism utilizes an Overhead Valve (OHV) arrangement driven by a gear-train-actuated camshaft located within the cylinder block. Valves are positioned vertically above the pistons within the cylinder head assembly to maximize volumetric efficiency during intake and exhaust strokes. Valve clearance adjustments must be performed mechanically using the rocker arm adjusters while referencing standard cold engine values during maintenance intervals. The internal combustion footprint consists of a total displacement of 1.1 liters (1115 cc). The precision cylinder design measures a bore diameter of 76 mm (2.99 in) paired with a piston stroke length of 82 mm (3.23 in).

Fuel delivery is managed via a reliable mechanical indirect injection (IDI) system. Pressurized fuel flow is executed by a mechanical inline fuel injection pump linked directly to a mechanical governor system controlling engine speed regulation. Low-pressure fuel transfer relies on a standard 12V electric, self-priming fuel lift pump designed to automate system air bleeding procedures. High-pressure lines supply individual fuel injectors that atomize fuel into a swirling pre-combustion chamber rather than directly into the main cylinder cavity. Cold start operation is assisted by integrated 12V electric glow plugs positioned within the pre-combustion chambers to ensure rapid ignition under sub-zero ambient conditions.

Engine lubrication is driven by a high-efficiency internal oil pump that directs pressurized engine oil through critical galleries to main bearings, connecting rod journals, and the upper valve train. Thermal regulation is achieved through a heavy-duty, liquid-cooled closed-circuit system. Coolant circulation is forced via a belt-driven water pump, managing a total internal engine coolant capacity of 0.95 quarts (0.9 liters), excluding external radiator capacity.

General Technical Data

Engine Specifications

Engine Model ............... Isuzu 3CB1
Engine Type ............... 4-cycle inline 3-cylinder indirect injection liquid-cooled diesel
Number of Cylinders ............... 3
Cylinder Arrangement ............... In-line vertical
Engine Bore, in (mm) ............... 2.99 (76.0)
Engine Stroke, in (mm) ............... 3.23 (82.0)
Displacement, cu.in (L) ............... 68.1 (1.116)
Rated Engine Power, hp (kW) ............... 25.1 (18.7) at 3200 rpm
Continuous Engine Power, hp (kW) ............... 21.3 (15.9) at 3200 rpm
Rated Engine Speed, rpm ............... 3200
Peak Torque ............... 46.8 lb-ft (63.5 Nm) at 2300 rpm
Idle Speed, rpm ............... 900-1000
No Load Maximum Speed, rpm ............... 3400
Aspiration Type ............... Naturally Aspirated
Compression Ratio ............... 23.5:1
Firing Order ............... 1-3-2
Combustion Chamber Type ............... Swirl chamber indirect injection
Engine Rotation Direction ............... Counterclockwise viewed from flywheel interface
Valve Train Layout ............... Overhead valve pushrod configuration
Valves Per Cylinder ............... 2
Cylinder Block Type ............... Cast iron alloy monoblock
Cylinder Head Type ............... Cast iron single piece overhead valve structure
Lubrication System ............... Full-pressure forced lubrication feed
Oil Pump Type ............... Trochoid gear-driven rotor assembly
Oil Filter Type ............... Full-flow cartridge spin-on paper element
Cooling System ............... Forced liquid circulation thermal control
Water Pump Type ............... Belt-driven centrifugal impeller module
Thermostat Type ............... Wax pellet bypass control unit
Air Cleaner Type ............... Dry dual element heavy duty multi stage cleaner
Starting System ............... Electric motor starter mechanism
Electrical System Voltage, V ............... 12
Alternator Capacity, A ............... 20-35

Fuel System

Injection Pump Type ............... Bosch PFR mechanical in-line mini pump unit
Injection Pump Feed Pressure, psi (kPa) ............... 2.84-4.26 (19.6-29.4)
Fuel Injector Nozzle Type ............... Throttle type orifice tip assembly
Injection Valve Opening Pressure, psi (MPa) ............... 1991-2133 (13.7-14.7)
Fuel Filter Construction ............... Spin-on element with sediment bowl unit
Maximum Fuel Return Flow, qt/hr (L/hr) ............... 4.23 (4.0)
Fuel Transfer Pump Delivery, qt/min (L/min) ............... 0.85 (0.8)
Injection Pipe Outer Diameter, in (mm) ............... 0.236 (6.0)
Injection Pipe Inner Diameter, in (mm) ............... 0.078 (2.0)
Fuel Injection Timing ............... 18 deg BTDC
Governor Mechanism ............... Mechanical centrifugal flyweight layout
Fuel Lift Pump Type ............... Electric self priming supply assembly

Dimensions and Weight

Overall Length, in (mm) ............... 20.3-22.4 (520-570)
Overall Width, in (mm) ............... 17.3-17.9 (440-455)
Overall Height, in (mm) ............... 23.1 (586.0)
Dry Weight, lbs (kg) ............... 225-258 (102-117)

Maintenance Data

Service Information

Compression Pressure, Minimum, psi (MPa) ............... 441 (3.04)
Compression Pressure, Standard, psi (MPa) ............... 498 (3.43)
Maximum Allowed Cylinder Variance, psi (MPa) ............... 28.4 (0.196)
Oil Pressure at Idle Speed, psi (kPa) ............... 14.2 (98.1)
Oil Pressure at Rated Speed, psi (kPa) ............... 42.6-56.8 (294.0-392.0)
Thermostat Opening Temperature, F (C) ............... 160 (71)
Thermostat Full Open Level, F (C) ............... 185 (85)
Drive Belt Deflection Tension, in (mm) ............... 0.39-0.47 (10.0-12.0)
Intake Valve Clearance, Cold, in (mm) ............... 0.010 (0.25)
Exhaust Valve Clearance, Cold, in (mm) ............... 0.010 (0.25)

Engine Oil and Coolant

Engine Oil Type .................. SAE 10W-30 or SAE 15W-40
API Service Classifications ......................... CH-4 or CI-4
Engine Oil Capacity, qt (L) ............... 3.17 (3.0)
Minimum Oil Level Limit, qt (L) ............... 2.11 (2.0)
Coolant Total Jacket Capacity, qt (L) ............... 1.00 (0.95)

Service Intervals

Change oil and filter ............... Every 250 hours
Inspect air cleaner ............... Every 100 hours
Service air cleaner ............... Every 500 hours
Replace fuel filter ............... Every 500 hours
Valve clearance adjustment ............... Every 500 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 Standard Diameter, in (mm) ............... 2.9921-2.9933 (76.000-76.030)
Cylinder Bore Maximum, Wear Limit, in (mm) ............... 2.9992 (76.180)
Cylinder Bore Taper Ovality Limit, in (mm) ............... 0.00078 (0.020)
Crankshaft Main Journal Diameter, in (mm) ............... 1.9673-1.9685 (49.970-50.000)
Crankshaft Main Bearing Oil Clearance, in (mm) ............... 0.00137-0.00295 (0.035-0.075)
Crankshaft Crankpin Journal Diameter, in (mm) ............... 1.5736-1.5748 (39.970-40.000)
Crankpin Bearing Clearance, Max Limit, in (mm) ............... 0.00433 (0.110)
Crankshaft Runout, Maximum Limit, in (mm) ............... 0.00118 (0.030)
Crankshaft Center Journal Side Gap, in (mm) ............... 0.0023-0.0067 (0.060-0.170)
Crankshaft End Play, in (mm) ............... 0.0118 (0.300)
Main Journal Bearing Clearance, Limit, in (mm) ............... 0.00472 (0.120)
Connecting Rod Small End Bushing ID, in (mm) ............... 0.8669-0.8677 (22.020-22.040)
Connecting Rod Bearing Oil Clearance, in (mm) ............... 0.00137-0.00275 (0.035-0.070)
Connecting Rod Side Play, Standard, in (mm) ............... 0.0059-0.0098 (0.150-0.250)
Connecting Rod Side Play, Max Limit, in (mm) ............... 0.0137 (0.350)
Cylinder Head Surface Distortion, in (mm) ............... 0.00196 (0.050)
Intake Valve Stem Outer Diameter, in (mm) ............... 0.2342-0.2350 (5.950-5.970)
Exhaust Valve Stem Outer Diameter, in (mm) ............... 0.2338-0.2346 (5.940-5.960)
Valve Guide Inner Diameter, in (mm) ............... 0.2362-0.2370 (6.000-6.020)
Intake Valve Stem To Guide Clearance, in (mm) ............... 0.00118-0.00275 (0.030-0.070)
Exhaust Valve Stem To Guide Clearance, in (mm) ............... 0.00157-0.00314 (0.040-0.080)
Valve Stem To Guide Clearance, Max Limit, in (mm) ............... 0.00787 (0.200)
Valve Spring Free Length, Standard, in (mm) ............... 1.3779 (35.000)
Valve Spring Free Length, Service Limit, in (mm) ............... 1.3188 (33.500)
Camshaft Journal Diameter, in (mm) ............... 1.5732-1.5744 (39.960-39.990)
Camshaft Journal Oil Clearance, in (mm) ............... 0.0011-0.0031 (0.030-0.080)
Cam Lobe Height (Intake), in (mm) ............... 1.2952-1.2972 (32.900-32.950)
Cam Lobe Height (Exhaust), in (mm) ............... 1.2952-1.2972 (32.900-32.950)
Rocker Arm Shaft Outer Diameter, in (mm) ............... 0.4716-0.4724 (11.980-12.000)
Rocker Arm Bushing Inner Diameter, in (mm) ............... 0.4732-0.4744 (12.020-12.050)
Rocker Arm To Shaft Oil Clearance, in (mm) ............... 0.00078-0.00275 (0.020-0.070)
Rocker Arm Oil Clearance, Max Limit, in (mm) ............... 0.0059 (0.150)
Idler Gear Shaft Outer Diameter, in (mm) ............... 1.3366-1.3377 (33.950-33.980)
Idler Gear Bushing Inner Diameter, in (mm) ............... 1.3385-1.3401 (34.000-34.040)
Idler Gear Bushing Oil Clearance, in (mm) ............... 0.00078-0.00354 (0.020-0.090)
Piston Skirt Standard Diameter, in (mm) ............... 2.9897-2.9909 (75.940-75.970)
Piston To Cylinder Bore Clearance, in (mm) ............... 0.00196-0.00275 (0.050-0.070)
Piston Pin Bore Diameter, in (mm) ............... 0.8661-0.8665 (22.000-22.010)
Piston Pin Outer Diameter, in (mm) ............... 0.8657-0.8661 (21.990-22.000)
Piston Pin To Pin Bore Clearance, in (mm) ............... 0.000078-0.00047 (0.002-0.012)
Piston Pin To Connecting Rod Clearance, in (mm) ............... 0.00078-0.00196 (0.020-0.050)
Top Ring Side Clearance, in (mm) ............... 0.0023-0.0037 (0.060-0.095)
Second Ring Side Clearance, in (mm) ............... 0.0019-0.0033 (0.050-0.085)
Oil Ring Side Clearance, in (mm) ............... 0.0011-0.0027 (0.028-0.070)
Top Ring End Gap, in (mm) ............... 0.0059-0.0118 (0.150-0.300)
Second Ring End Gap, in (mm) ............... 0.0071-0.0137 (0.180-0.350)
Oil Ring End Gap, in (mm) ............... 0.0078-0.0157 (0.200-0.400)

Tightening Torques

Cylinder Head Bolts, lb-ft (Nm) ............... 44.3-50.2 (60.0-68.0)
Connecting Rod Cap Nut, lb-ft (Nm) ............... 22.1-25.1 (30.0-34.0)
Main Bearing Cap Bolts, lb-ft (Nm) ............... 36.9-42.8 (50.0-58.0)
Flywheel Assembly Mount Bolts, lb-ft (Nm) ............... 40.6-46.5 (55.0-63.0)
Crankshaft Center Pulley Bolt, lb-ft (Nm) ............... 65.0-72.3 (88.0-98.0)
Rocker Arm Bracket Shaft Bolts, lb-ft (Nm) ............... 15.9-20.3 (21.5-27.5)
Rocker Arm Adjusting Nut, lb-ft (Nm) ............... 8.7-13.0 (11.8-17.6)
Cylinder Head Valve Cover Top Nuts, lb-ft (Nm) ............... 5.1-7.2 (6.9-9.8)
Oil Pan Outer Perimeter Bolts, lb-ft (Nm) ............... 7.2-9.6 (9.8-13.0)
Oil Pan Bottom Drain Plug Bolt, lb-ft (Nm) ............... 21.7-28.9 (29.4-39.2)
Timing Gear Case Shield Bolts, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Camshaft Rear Thrust Retainer Bolts, lb-ft (Nm) ............... 7.2-10.8 (9.8-14.7)
Idler Gear Support Shaft Anchor Bolt, lb-ft (Nm) ............... 18.1-22.1 (24.5-30.0)
Fuel Injection Pump Mount Body Nuts, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Fuel Injection Pump Gear Drive Nut, lb-ft (Nm) ............... 28.9-36.1 (39.2-49.0)
Injection Nozzle Holder Body To Head, lb-ft (Nm) ............... 36.1-43.3 (49.0-58.8)
Injection Nozzle Retaining Cap Nut, lb-ft (Nm) ............... 25.3-29.4 (34.3-39.9)
High Pressure Fuel Line Flare Gland, lb-ft (Nm) ............... 18.1-21.7 (24.5-29.4)
Fuel Return Line Assembly Leak Nut, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Glow Plug Terminal Small Cable Nut, lb-ft (Nm) ............... 1.1-1.4 (1.5-2.0)
Water Pump Assembly Mounting Bolts, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Cooling Fan Blade Core Mount Bolts, lb-ft (Nm) ............... 5.1-7.2 (6.9-9.8)
Thermostat Housing Top Cover Bolts, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Oil Filter Internal Bypass Relief Valve, lb-ft (Nm) ............... 18.1-25.3 (24.5-34.3)
Starter Motor Frame Flange Mount Bolts, lb-ft (Nm) ............... 36.1-47.0 (49.0-63.7)
Starter Main Battery Terminal Stud Nut, lb-ft (Nm) ............... 6.5-8.7 (8.8-11.8)
Alternator Pivot Support Swing Bolt, lb-ft (Nm) ............... 25.3-32.5 (34.3-44.1)
Alternator Adjusting Slide Link Bolt, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Exhaust Manifold Flange Fastener Nuts, lb-ft (Nm) ............... 18.1-22.1 (24.5-30.0)
Intake Manifold Air Duct Inverted Bolts, lb-ft (Nm) ............... 14.5-18.1 (19.6-24.5)
Flywheel Housing Cover Structural Bolts, lb-ft (Nm) ............... 18.1-25.3 (24.5-34.3)
Oil Pipe Flange Joint Connect Screws, lb-ft (Nm) ............... 7.2-10.8 (9.8-14.7)
Fuel Filter Bracket Main Frame Bolts, lb-ft (Nm) ............... 18.1-25.3 (24.5-34.3)
Air Cleaner Mounting Band Bracket Bolts, lb-ft (Nm) ............... 14.5-21.7 (19.6-29.4)

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• Isuzu Engines Specs
  
• Isuzu 2AA1 Specs
  
• Isuzu 3AA1 Specs
  
• Isuzu 3AB1 Specs
  
• Isuzu 3CD1 Specs
  
• Isuzu 3CE1 Specs
  
• Isuzu 3CH1 Specs
  

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