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Isuzu 2AA1 Engine

The Isuzu 2AA1 is an industrial-grade, two-cylinder, inline diesel engine developed by Isuzu Motors. Produced from 1972 to 1989, this liquid-cooled power unit was primarily designed for heavy-duty applications, including agricultural tractors (such as the Iseki TS1610), small construction machinery, and stationary generator sets. Built on a rigid cast-iron block structure, it shares its internal architecture with the larger C190 four-cylinder and 3AA1 three-cylinder engine series. This design provides enhanced parts compatibility and simplifies workshop maintenance.

The engine utilizes a two-cylinder in-line layout. The valve configuration follows an Overhead Valve (OHV) design, with the valves actuated by a gear-driven camshaft via pushrods and rocker arms. Total Displacement: 975 cc (59.5 cubic inches). Cylinder Bore: 86 mm (3.39 inches). Piston Stroke: 84 mm (3.31 inches). The engine uses a full-pressure lubrication circuit powered by a trochoid-type oil pump driven directly by the crankshaft gear. Engine oil passes through a full-flow cartridge filter element before reaching the main bearings, connecting rod journals, and rocker mechanism.

The fuel injection circuit utilizes an indirect injection system with a pre-combustion chamber design. Fuel pressurized by a mechanical lift pump is fed into a high-pressure, in-line Bosch PES-A type injection pump. This injection pump is synchronized directly via the engine timing gear train. It distributes fuel through steel high-pressure lines to the mechanical injection nozzles, which atomize fuel into the pre-combustion chambers. Engine speed regulation is sustained by a mechanical flyweight governor integrated directly within the injection pump housing.

The unit features a forced liquid-cooling layout. A centrifugal water pump, driven by a V-belt from the crankshaft pulley, circulates coolant through the cylinder block jackets and cylinder head. Temperature management is regulated by a wax-pellet type thermostat positioned at the water outlet housing to control bypass flow to the radiator.

General Technical Data

Engine Specifications

Engine Model ............... Isuzu 2AA1
Engine Type ............... 4-cycle inline 2-cylinder OHV liquid-cooled diesel
Number of Cylinders ............... 2
Cylinder Arrangement ............... In-line vertical configuration
Engine Bore, in (mm) ............... 3.39 (86.0)
Engine Stroke, in (mm) ............... 3.31 (84.0)
Displacement, cu.in (cc) ............... 59.5 (975)
Compression Ratio ............... 20.0:1
Rated Engine Power, hp (kW) ............... 29.1 (21.7)
Rated Engine Speed, rpm ............... 2800
Max No-Load Speed, rpm ............... 3050
Minimum Idle Speed, rpm ............... 800
Aspiration Type ............... Naturally aspirated
Firing Order ............... 1-2
Combustion Chamber ............... Swirl chamber pre-combustion design
Rotation Direction ............... Counterclockwise viewed from flywheel side
Cylinder Block Material ............... Cast iron alloy heavy-duty construction
Cylinder Head Material ............... Cast iron mono-block construction
Number of Main Bearings ............... 3 journal locations
Valves per Cylinder ............... 2 valves per cylinder assembly
Valve Arrangement ............... Overhead valve pushrod actuated mechanism
Cooling System ............... Liquid-cooled forced circulation
Water Pump Type ............... Belt-driven centrifugal
Lubrication System ............... Full-pressure
Oil Pump Type ............... Trochoid gear-driven style
Oil Filter Type ............... Full-flow cartridge spin-on
Air Cleaner Type ............... Dry element
Starting System Type ............... Electric starter
Electrical System ............... 12V

Fuel System

Fuel Injection Type ............... Indirect injection with integrated glow plug
Fuel Injection Pump Type ............... Bosch PFR in-line multi-plunger
Fuel Injection Nozzle Type ............... Throttle type nozzle assembly pin design
Fuel Injection Delivery Valve Type ............... Retraction volume, check valve system
Injection Pressure, psi (MPa) ............... 1706-1849 (11.8-12.7)
Fuel Injection Timing, deg BTDC ............... 18-20
Fuel Filter Type ............... Spin-on element cartridge filter
Fuel Feed Pump Type ............... Mechanical diaphragm transfer pump
Maximum Fuel Inlet Restriction, in Hg (kPa) ............... 4.0 (13.5)
Maximum Fuel Return Restriction, in Hg (kPa) ............... 5.9 (20.0)
Fuel Line Diameter, in (mm) ............... 0.24 (6.0)
Governor Type ............... Mechanical centrifugal variable speed
Fuel Transfer Pump Delivery Pressure, psi (kPa) ............... 2.8-4.3 (19.3-29.6)
Fuel Injection Pump Governor Advance Line, deg ............... 0.00-2.00
Fuel Return Line Temperature Limit, F (C) ............... 140 (60)
Fuel Injection Plunger Diameter, in (mm) ............... 0.216 (5.5)
Fuel Injection Plunger Stroke, in (mm) ............... 0.275 (7.0)
Injection Nozzle Holder Type ............... Flange mount or screw-in body style mount

Dimensions and Weight

Overall Length, in (mm) ............... 21.5 (545)
Overall Width, in (mm) ............... 19.9 (505)
Overall Height, in (mm) ............... 26.3 (670)
Dry Weight, lbs (kg) ............... 353 (160)
Wet Weight, lbs (kg) ............... 375 (170)

Maintenance Data

Service Information

Compression Pressure, psi (MPa) ............... 426-455 (2.94-3.14)
Minimum Compression Pressure, psi (MPa) ............... 341 (2.35)
Maximum Cylinder Pressure, psi (MPa) ............... 28.4 (0.20)
Coolant Temperature Normal Range, F (C) ............... 167-194 (75-90)
Thermostat Opening Temperature, F (C) ............... 169-176 (76.5-80.0)
Thermostat Full Open Temperature, F (C) ............... 194 (90)
Oil Pressure at Rated Speed, psi (kPa) ............... 42.6-56.8 (294-392)
Oil Pressure at Idle Speed, psi (kPa) ............... 14.2 (98)
Oil Pressure Relief Valve Opening Point, psi (kPa) ............... 64.0-78.2 (441-539)
Fan Belt Tension Deflection, in (mm) ............... 0.39-0.47 (10.0-12.0)
Valve Clearance (Intake, Cold), in (mm) ............... 0.012-0.014 (0.30-0.35)
Valve Clearance (Exhaust, Cold), in (mm) ............... 0.012-0.014 (0.30-0.35)

Engine Oil and Coolant

Engine Oil Type .................. SAE 30, 10W-30, or 15W-40
API Service Classifications ......................... CC or CD
Engine Oil Capacity with Filter, qt (L) ............... 4.76 (4.5)
Engine Oil Capacity without Filter, qt (L) ............... 4.23 (4.0)
Cooling System Fluid Capacity, qt (L) ............... 5.28 (5.0)

Service Intervals

Change oil and filter ............... Every 100 hours
Service air cleaner ............... Every 50 hours
Replace air cleaner ............... Every 250 hours
Replace fuel filter ............... Every 200 hours
Valve clearance adjustment ............... Every 400 hours
Fuel system inspection ............... Every 500 hours
Change coolant ............... Every 1000 hours
Compression test ............... Every 500 hours
Belt inspection ............... Every service cycle

Service Specifications

Cylinder Bore Standard Diameter, in (mm) ............... 3.3858-3.3874 (86.000-86.040)
Cylinder Bore Max Wear Limit, in (mm) ............... 3.3937 (86.200)
Cylinder Bore Taper, Wear Limit, in (mm) ............... 0.0008 (0.020)
Cylinder Bore Out of Round, Limit, in (mm) ............... 0.0008 (0.020)
Cylinder Liner Inside Diameter, in (mm) ............... 3.3858-3.3870 (86.000-86.030)
Cylinder Head Lower Surface Flatness Distortion, in (mm) ............... 0.0020 (0.050)
Cylinder Block Upper Surface Flatness Distortion, in (mm) ............... 0.0020 (0.050)
Connecting Rod Small End Bushing I.D, in (mm) ............... 0.9846-0.9852 (25.010-25.025)
Crankshaft Main Journal Diameter, in (mm) ............... 2.4390-2.4398 (61.950-61.970)
Crankshaft Main Journal Oil Clearance, in (mm) ............... 0.0013-0.0033 (0.034-0.084)
Crankshaft Free End Play, in (mm) ............... 0.0031-0.0070 (0.080-0.180)
Piston Outer Diameter, in (mm) ............... 3.3819-3.3835 (85.900-85.940)
Piston to Cylinder Wall Clearance, in (mm) ............... 0.0039-0.0055 (0.100-0.140)
Piston Pin Outer Diameter, in (mm) ............... 0.9841-0.9844 (24.995-25.002)
Piston Pin to Piston Bushing Clearance, in (mm) ............... 0.0001-0.0005 (0.002-0.012)
Top Ring Groove Width, in (mm) ............... 0.0807-0.0815 (2.050-2.070)
Second Ring Groove Width, in (mm) ............... 0.0807-0.0815 (2.050-2.070)
Third Ring Groove Width, in (mm) ............... 0.0807-0.0815 (2.050-2.070)
Oil Ring Groove Width, in (mm) ............... 0.1783-0.1791 (4.530-4.550)
Top Ring Side Clearance, in (mm) ............... 0.0027-0.0043 (0.070-0.110)
Second Ring Side Clearance, in (mm) ............... 0.0020-0.0035 (0.050-0.090)
Oil Ring Side Clearance, in (mm) ............... 0.0012-0.0027 (0.030-0.070)
Top Ring End Gap, in (mm) ............... 0.0098-0.0157 (0.250-0.400)
Second Ring End Gap, in (mm) ............... 0.0078-0.0137 (0.200-0.350)
Oil Ring End Gap, in (mm) ............... 0.0078-0.0137 (0.200-0.350)
Valve Stem Outer Diameter (Intake), in (mm) ............... 0.3129-0.3137 (7.950-7.970)
Valve Stem Outer Diameter (Exhaust), in (mm) ............... 0.3118-0.3126 (7.920-7.940)
Valve Stem to Valve Guide Clearance (Intake), in (mm) ............... 0.0011-0.0025 (0.030-0.065)
Valve Stem to Valve Guide Clearance (Exhaust), in (mm) ............... 0.0023-0.0037 (0.060-0.095)
Valve Guide Inside Diameter, in (mm) ............... 0.3150-0.3155 (8.000-8.015)
Valve Face Angle, deg ............... 45
Valve Seat Angle, deg ............... 45
Valve Seat Contact Width (Intake), in (mm) ............... 0.047-0.055 (1.20-1.40)
Valve Seat Contact Width (Exhaust), in (mm) ............... 0.047-0.055 (1.20-1.40)
Valve Spring Free Vertical Lenght, in (mm) ............... 1.689 (42.90)
Camshaft Journal Outer Diameter (Front), in (mm) ............... 1.5728-1.5738 (39.950-39.975)
Camshaft Journal Outer Diameter (Middle), in (mm) ............... 1.5728-1.5738 (39.950-39.975)
Camshaft Journal Outer Diameter (Rear), in (mm) ............... 1.5728-1.5738 (39.950-39.975)
Camshaft Journal Bearing Oil Clearance, in (mm) ............... 0.0009-0.0033 (0.025-0.085)
Cam Lobe Height (Intake), in (mm) ............... 1.4586-1.4594 (37.050-37.070)
Cam Lobe Height (Exhaust), in (mm) ............... 1.4586-1.4594 (37.050-37.070)
Camshaft End Play, in (mm) ............... 0.0019-0.0059 (0.050-0.150)
Rocker Arm Shaft Outer Diameter, in (mm) ............... 0.7468-0.7476 (18.970-18.990)
Rocker Arm Bushing Inside Diameter, in (mm) ............... 0.7480-0.7492 (19.000-19.030)
Rocker Arm to Shaft Running Clearance, in (mm) ............... 0.0003-0.0023 (0.010-0.060)
Tappet Lifter Barrel Outer Diameter, in (mm) ............... 0.8251-0.8259 (20.960-20.980)
Tappet Lifter Guide Block Tunnel I.D, in (mm) ............... 0.8267-0.8279 (21.000-21.030)
Tappet Lifter to Block Tunnel Clearance, in (mm) ............... 0.0007-0.0027 (0.020-0.070)
Crankshaft Timing Gear Backlash Clearance, in (mm) ............... 0.0019-0.0043 (0.050-0.110)
Camshaft Timing Gear Backlash Clearance, in (mm) ............... 0.0019-0.0043 (0.050-0.110)

Tightening Torques

Cylinder Head Bolts (1-Stage), lb-ft (Nm) ............... 36.1 (49.0)
Cylinder Head Bolts (2-Stage), lb-ft (Nm) ............... 57.8 (78.4)
Cylinder Head Bolts (3-Stage), lb-ft (Nm) ............... 72.3-79.5 (98.0-107.8)
Main Bearing Cap Bolts, lb-ft (Nm) ............... 79.5-86.7 (107.8-117.6)
Connecting Rod Cap Nuts, lb-ft (Nm) ............... 57.8-65.0 (78.4-88.2)
Flywheel Mounting to Crankshaft Bolts, lb-ft (Nm) ............... 86.7-93.9 (117.6-127.4)
Crankshaft Front Pulley Nut, lb-ft (Nm) ............... 130.1-144.6 (176.4-196.0)
Camshaft Thrust Plate Bolts, lb-ft (Nm) ............... 14.5-21.7 (19.6-29.4)
Rocker Arm Shaft Support Screws, lb-ft (Nm) ............... 21.7-28.9 (29.4-39.2)
Valve Timing Gear Case Cover Bolts, lb-ft (Nm) ............... 14.5-21.7 (19.6-29.4)
Engine Oil Pan Drain Plug Screw, lb-ft (Nm) ............... 57.8-72.3 (78.4-98.0)
Flywheel Housing to Block Mounting Bolts, lb-ft (Nm) ............... 57.8-65.0 (78.4-88.2)
Exhaust Manifold Mounting Nuts, lb-ft (Nm) ............... 18.1-25.3 (24.5-34.3)
Intake Manifold Mounting Bolts, lb-ft (Nm) ............... 14.5-21.7 (19.6-29.4)
Fuel Injection Pump Housing Mounting Nuts, lb-ft (Nm) ............... 14.5-21.7 (19.6-29.4)
Fuel Injection Nozzle Holder Body Screws, lb-ft (Nm) ............... 43.4-50.6 (58.8-68.6)
Fuel High Pressure Injection Line Flare Nuts, lb-ft (Nm) ............... 21.7-25.3 (29.4-34.3)
Fuel Injection Nozzle Leak Off Leakage Pipe Nut, lb-ft (Nm) ............... 18.1-21.7 (24.5-29.4)
Water Pump Assembly Mounting Shell Bolts, lb-ft (Nm) ............... 14.5-21.7 (19.6-29.4)
Oil Pump Assembly Base Bolts, lb-ft (Nm) ............... 14.5-21.7 (19.6-29.4)
Oil Pressure Switch Sensor, lb-ft (Nm) ............... 10.8-14.5 (14.7-19.6)
Starter Motor Mounting Flange Bolts, lb-ft (Nm) ............... 57.8-72.3 (78.4-98.0)
Alternator Pivot Mount Long Support Bolt, lb-ft (Nm) ............... 28.9-36.1 (39.2-49.0)

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• Isuzu Engines Specs
  
• Isuzu 3AA1 Specs
  
• Isuzu 3AB1 Specs
  
• Isuzu 3CB1 Specs
  
• Isuzu 3CD1 Specs
  
• Isuzu 3CE1 Specs
  
• Isuzu 3CH1 Specs
  

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