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Mitsubishi K3H Engine

The Mitsubishi K3H is a vertical, water-cooled, 4-stroke, 3-cylinder in-line diesel engine belonging to the industrial Mitsubishi K-series. Designed for compactness, fuel efficiency, and high torque output at low operating stress, this naturally aspirated engine is heavily utilized in agricultural machinery (such as the Mitsubishi MT250 and MT280D compact tractors), mini excavators, and stationary industrial equipment like generator sets. The cast-iron crankcase features the engine model embossed directly on the block for field identification.

The cylinder head utilizes an overhead valve (OHV) layout with 2 valves per cylinder (3 intake valves and 3 exhaust valves in total across the inline configuration). The valves are actuated via a conventional camshaft, pushrods, and rocker arm assembly. Intake Valve Diameter: 30 mm. Exhaust Valve Diameter: 28 mm. Bore: 78 mm (3.071 inches). Stroke: 90 mm (3.543 inches). Total Displacement: 1.290 Liters (1290 cc / 78.7 cubic inches).

Fuel System: Fuel delivery is managed via an indirect injection (IDI) combustion design using swirl chambers to ensure clean fuel combustion and optimal cold-starting performance. Injection Pump Type: An integrated, in-line 3-cylinder high-pressure fuel injection pump built directly into the engine framework. Control Apparatus: A mechanical centrifugal governor regulates fuel delivery across the RPM band. The assembly features built-in "smoke set" (fuel-limiting mechanism during start/acceleration) and "Angleich" (torque-control) devices to optimize fuel economy and manage exhaust emissions. Timing Adjustments: Injection timing synchronization is adjusted manually by altering the thickness of the shim packs located beneath the injection pump mounting flange.

The engine uses a full-force, pressure-fed lubrication circuit pressurized by a crankshaft-driven trochoid gear pump. Oil flows through a full-flow, spin-on cartridge filter element before reaching the main bearings, connecting rod journals, and rocker shafts. Thermal regulation is maintained via a closed-loop, forced-circulation liquid cooling system. The circuit is managed by a belt-driven centrifugal water pump that circulates coolant through the engine block, cylinder head channels, and an external radiator setup. A cooling fan mounted to the water pump pulley provides forced airflow across the radiator core.

General Technical Data

Engine Specifications

Engine Model ............... Mitsubishi K3H
Engine Type ............... 4-cycle water-cooled vertical inline diesel engine
Number of Cylinders ............... 3
Cylinder Arrangement ............... In-line
Engine Bore, in (mm) ............... 3.071 (78.0)
Engine Stroke, in (mm) ............... 3.543 (90.0)
Displacement, cu.in (L) ............... 78.72 (1.290)
Rated Engine Power, hp (kW) ............... 25.0-28.0 (18.6-20.8)
Rated Engine Speed, rpm ............... 2700
Peak Torque ............... 54.2 lb-ft (73.5 Nm) at 1600-1800 rpm
Idle Speed ............... 800-900 rpm
Aspiration Type ............... Naturally Aspirated
Compression Ratio ............... 22.0:1-23.0:1
Firing Order ............... 1-3-2
Combustion Chamber ............... Swirl pre-combustion chamber type
Crankshaft Type ............... Forged carbon steel
Main Bearings Type ............... Tri-metal steel-backed alloy inserts
Camshaft Type ............... Chill cast iron gear driven cluster
Valve Mechanism ............... Overhead valve
Rotation Direction ............... Counter-clockwise viewed from flywheel side
Cylinder Block Type ............... Cast iron monoblock
Cylinder Head Type ............... Cast iron cross-flow crosshead design
Lubrication System ............... Forced circulation pressure feed
Oil Pump Type ............... Trochoid gear pump
Oil Filter Type ............... Full-flow cartridge spin-on paper element
Cooling System ............... Liquid-cooled radiator with forced circulation
Water Pump Type ............... Belt-driven centrifugal impeller pump
Air Cleaner Type ............... Dry heavy duty dual stage paper element
Starting System ............... Electrical solenoid reduction engagement motor
Electrical System ............... 12V

Fuel System

Injection Pump Model ............... Bosch M mini type in-line plunger assembly
Injection Pump Delivery pressure ............... 1991-2133 psi (13.7-14.7 MPa)
Injection Nozzle Holder Type ............... Bosch flange fit nozzle housing
Injection Nozzle Tip Type ............... Throttle pintle style nozzle assembly
Injection Opening Pressure, psi (bar) ............... 1706-1849 (118-128)
Injection Timing, deg BTDC ............... 21.0
Governor Type ............... Centrifugal flyweight mechanical
Fuel Filter Type ............... Spin-on replaceable paper element cartridge
Fuel Feed Pump Type ............... Mechanical cam driven diaphragm style unit
Fuel System Venting Mechanism ............... Manual air bleed overflow valve assembly
Fuel Requirements ............... High speed diesel fuel ASTM D975 No. 2D grade
Plunger Diameter, in (mm) ............... 0.216 (5.5)
Plunger Stroke, in (mm) ............... 0.275 (7.0)
Delivery Valve Opening Pressure ............... 497-639 psi (3.43-4.41 MPa)
Pre-combustion Jet Angle ............... 15.0 deg

Dimensions and Weight

Overall Length, in (mm) ............... 20.3 (515)
Overall Width, in (mm) ............... 17.5 (445)
Overall Height, in (mm) ............... 21.8 (555)
Dry Weight, lbs (kg) ............... 276 (125)

Maintenance Data

Service Information

Compression Pressure, standard limit, psi (bar) ............... 426.7 (29.4)
Compression Pressure, service limit, psi (bar) ............... 341.3 (23.5)
Maximum Pressure Difference Between Cylinders ............... 35.5 psi (2.45 bar)
Thermostat Opening Start Temperature, F (C) ............... 160.0 (71.0)
Thermostat Full Open Temperature, F (C) ............... 185.0 (85.0)
Oil Pressure Switch Tripping Limit ............... 7.11 psi (0.49 bar)
Oil Pressure Operating Range ............... 28.4-56.9 psi (1.96-3.92 bar)
V-Belt Deflection Tension............... 0.39-0.47 in (10.0-12.0 mm)
Intake Valve Clearance, in (mm) ............... 0.0098 (0.25)
Exhaust Valve Clearance, in (mm) ............... 0.0098 (0.25)

Engine Oil and Coolant

Engine Oil Type .................. SAE 30W, SAE 10W-30, or 15W-40
API Service Classifications ......................... CD, CE, or CF-4
Engine Oil Capacity, qt (L) ............... 3.17 (3.0)
Engine Oil Capacity, Low level, qt (L) ............... 1.90 (1.8)
Coolant Total Capacity, qt (L) ............... 4.23 (4.0)

Service Intervals

Change oil and filter ............... Every 200 hours
Inspect air cleaner ............... Every 50 hours
Replace air cleaner ............... Every 500 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 800 hours
Clean radiator core ............... Every 250 hours
Inspect belt tension ............... Every 250 hours

Service Specifications

Cylinder Bore Inner Diameter, in (mm) ............... 3.0708-3.0720 (78.000-78.030)
Cylinder Bore Ovality Taper ............... 0.00039 in (0.010 mm) direction difference
Cylinder Liner Shim Thickness ............... 0.0039 in (0.10 mm) or 0.0078 in (0.20 mm)
Connecting Rod Small End Bushing I.D, in (mm) ............... 0.9059-0.9066 (23.012-23.030)
Connecting Rod Small End Bushing Clearance, in (mm) ............... 0.00047-0.00145 (0.012-0.037)
Connecting Rod Big End Inner Diameter, in (mm) ............... 1.8898-1.8905 (48.000-48.015)
Connecting Rod Bearing Oil Clearance, in (mm) ............... 0.0013-0.0033 (0.035-0.085)
Connecting Rod Big End Side Clearance, in (mm) ............... 0.0039-0.0137 (0.10-0.35)
Crankpin Journal Outer Diameter, in (mm) ............... 1.8492-1.8500 (46.970-46.990)
Crankshaft Main Journal Outer Diameter, in (mm) ............... 2.0461-2.0468 (51.970-51.990)
Crankshaft Thrust Washer Thickness, in (mm) ............... 0.0787-0.0807 (2.000-2.050)
Crankshaft End Play, in (mm) ............... 0.0019-0.0068 (0.05-0.175)
Main Bearing Shell Inner Diameter, in (mm) ............... 2.0480-2.0494 (52.020-52.056)
Main Bearing Oil Clearance, in (mm) ............... 0.0011-0.0033 (0.030-0.086)
Piston Outer Diameter, in (mm) ............... 3.0679-3.0691 (77.925-77.955)
Piston to Cylinder Bore Clearance, in (mm) ............... 0.00236-0.00374 (0.060-0.095)
Piston Pin Bore Inner Diameter, in (mm) ............... 0.9056-0.9060 (23.003-23.014)
Piston Pin Outer Diameter, in (mm) ............... 0.9052-0.9055 (22.993-23.000)
Piston Pin to Piston Bore Clearance, in (mm) ............... 0.00011-0.00082 (0.003-0.021)
Top Ring Groove Width, in (mm) ............... 0.0799-0.0807 (2.030-2.050)
Second Ring Groove Width, in (mm) ............... 0.0791-0.0799 (2.010-2.030)
Oil Ring Groove Width, in (mm) ............... 0.1578-0.1586 (4.010-4.030)
Top Ring Side Clearance, in (mm) ............... 0.0027-0.0043 (0.070-0.110)
Second Ring Side Clearance, in (mm) ............... 0.0015-0.0031 (0.040-0.080)
Oil Ring Side Clearance, in (mm) ............... 0.0007-0.0023 (0.020-0.060)
Top Ring End Gap, in (mm) ............... 0.0059-0.0118 (0.15-0.30)
Second Ring End Gap, in (mm) ............... 0.0059-0.0118 (0.15-0.30)
Oil Ring End Gap, in (mm) ............... 0.0078-0.0157 (0.20-0.40)
Cylinder Block Top Surface Distortion ............... 0.0019 in (0.05 mm)
Cylinder Head Bottom Surface Flatness ............... 0.0019 in (0.05 mm)
Intake Valve Stem Outer Diameter, in (mm) ............... 0.2740-0.2746 (6.960-6.975)
Exhaust Valve Stem Outer Diameter, in (mm) ............... 0.2730-0.2736 (6.935-6.950)
Intake Valve Stem to Guide Clearance, in (mm) ............... 0.00098-0.00236 (0.025-0.060)
Exhaust Valve Stem to Guide Clearance, in (mm) ............... 0.00196-0.00334 (0.050-0.085)
Valve Seat Face Angle, deg ............... 45.0
Valve Face Refacing Angle, deg ............... 45.0
Valve Seat Width, in (mm) ............... 0.0472-0.0591 (1.20-1.50)
Valve Head Thickness, in (mm) ............... 0.0394 (1.00)
Valve Spring Free Length, in (mm) ............... 1.567 (39.80)
Camshaft Journal Outer Diameter (Front), in (mm) ............... 1.5732-1.5740 (39.960-39.980)
Camshaft Journal Outer Diameter (Center), in (mm) ............... 1.5338-1.5346 (38.960-38.980)
Camshaft Journal Outer Diameter (Rear), in (mm) ............... 1.4945-1.4952 (37.960-37.980)
Camshaft Bushing Inner Diameter (Front), in (mm) ............... 1.5748-1.5763 (40.000-40.040)
Camshaft Bearing Bore Inner Diameter (Center), in (mm) ............... 1.5354-1.5366 (39.000-39.030)
Camshaft Bearing Bore Inner Diameter (Rear), in (mm) ............... 1.4960-1.4972 (38.000-38.030)
Camshaft Journal Oil Clearance (Front), in (mm) ............... 0.0007-0.0031 (0.020-0.080)
Camshaft Journal Oil Clearance (Center), in (mm) ............... 0.0007-0.0027 (0.020-0.070)
Camshaft Journal Oil Clearance (Rear), in (mm) ............... 0.0007-0.0027 (0.020-0.070)
Cam Lobe Height (Intake), in (mm) ............... 1.2858-1.2881 (32.660-32.720)
Cam Lobe Height (Exhaust), in (mm) ............... 1.2858-1.2881 (32.660-32.720)
Camshaft End Play, in (mm) ............... 0.0019-0.0059 (0.05-0.15)
Rocker Arm Shaft Outer Diameter, in (mm) ............... 0.4716-0.4722 (11.980-11.995)
Rocker Arm Bushing Inner Diameter, in (mm) ............... 0.4724-0.4731 (12.000-12.018)
Rocker Arm to Shaft Clearance, in (mm) ............... 0.0002-0.0015 (0.005-0.038)
Tappet Outer Diameter, in (mm) ............... 0.7462-0.7470 (18.955-18.976)
Tappet Guide Bore Inner Diameter, in (mm) ............... 0.7480-0.7488 (19.000-19.021)
Tappet to Guide Bore Clearance, in (mm) ............... 0.0009-0.0025 (0.024-0.066)
Idler Gear Shaft Outer Diameter, in (mm) ............... 0.7863-0.7870 (19.973-19.990)
Idler Gear Bushing Inner Diameter, in (mm) ............... 0.7874-0.7882 (20.000-20.021)
Idler Gear Bushing to Shaft Clearance, in (mm) ............... 0.00039-0.00188 (0.010-0.048)
Timing Gear Backlash (Crankshaft to Idler), in (mm) ............... 0.0019-0.0059 (0.05-0.15)
Timing Gear Backlash (Idler to Camshaft), in (mm) ............... 0.0019-0.0059 (0.05-0.15)
Timing Gear Backlash (Idler to Injection Pump), in (mm) ............... 0.0019-0.0059 (0.05-0.15)

Tightening Torques

Cylinder Head Bolt (Stage 1), lb-ft (Nm) ............... 25.3 (34.3)
Cylinder Head Bolt (Stage 2), lb-ft (Nm) ............... 50.6 (68.6)
Cylinder Head Bolt (Stage 3), lb-ft (Nm) ............... 75.9-83.1 (103.0-112.7)
Connecting Rod Cap Nut, lb-ft (Nm) ............... 36.1-39.7 (49.0-53.9)
Main Bearing Cap Bolt, lb-ft (Nm) ............... 57.8-65.0 (78.4-88.2)
Flywheel Retaining Bolt, lb-ft (Nm) ............... 83.1-90.4 (112.7-122.5)
Crankshaft Pulley Center Nut, lb-ft (Nm) ............... 108.4-122.9 (147.0-166.6)
Camshaft Thrust Plate Bolt, lb-ft (Nm) ............... 14.5-18.0 (19.6-24.5)
Rocker Arm Shaft Bracket Holding Bolt, lb-ft (Nm) ............... 21.7-28.9 (29.4-39.2)
Cylinder Head Cover Acorn Cap Nut, lb-ft (Nm) ............... 5.1-8.7 (6.9-11.8)
Oil Pan Drain Plug, lb-ft (Nm) ............... 36.1-43.4 (49.0-58.8)
Oil Pan Perimeter Attachment Bolt, lb-ft (Nm) ............... 14.5-18.0 (19.6-24.5)
Timing Gear Case Cover Outer Bolt, lb-ft (Nm) ............... 14.5-18.0 (19.6-24.5)
Timing Gear Case Back Plate Block Bolt, lb-ft (Nm) ............... 18.0-25.3 (24.5-34.3)
Flywheel Housing Attachment Bolt, lb-ft (Nm) ............... 43.4-50.6 (58.8-68.6)
Idler Gear Shaft Lock Bolt, lb-ft (Nm) ............... 21.7-28.9 (29.4-39.2)
Injection Pump Delivery Valve Holder, lb-ft (Nm) ............... 28.9-36.1 (39.2-49.0)
Injection Pump Mounting Flange Nut, lb-ft (Nm) ............... 14.5-18.0 (19.6-24.5)
Injection Nozzle Assembly into Cylinder Head, lb-ft (Nm) ............... 50.6-57.8 (68.6-78.4)
Fuel Leak-off Line Pipe Union Nut, lb-ft (Nm) ............... 18.0-21.7 (24.5-29.4)
High Pressure Fuel Injection Line Nut, lb-ft (Nm) ............... 18.0-25.3 (24.5-34.3)
Glow Plug Hex Assembly Installation, lb-ft (Nm) ............... 10.8-14.5 (14.7-19.6)
Glow Plug Electrical Power Cable Nut, lb-ft (Nm) ............... 1.1-1.4 (1.5-2.0)
Oil Pressure Switch Sensor Unit, lb-ft (Nm) ............... 10.8-14.5 (14.7-19.6)
Water Temperature Sender Unit, lb-ft (Nm) ............... 18.0-25.3 (24.5-34.3)
Thermostat Housing Cover Retaining Bolt, lb-ft (Nm) ............... 14.5-18.0 (19.6-24.5)
Water Pump Assembly Base Attachment Bolt, lb-ft (Nm) ............... 14.5-18.0 (19.6-24.5)
Water Pump Fan Pulley Structural Nut, lb-ft (Nm) ............... 36.1-43.4 (49.0-58.8)
Intake Manifold Block Mounting Bolt, lb-ft (Nm) ............... 14.5-18.0 (19.6-24.5)
Exhaust Manifold Block Mounting Bolt, lb-ft (Nm) ............... 18.0-25.3 (24.5-34.3)
Oil Pump Cover Plate Screws assembly, lb-ft (Nm) ............... 5.1-7.2 (6.9-9.8)
Oil Pressure Relief Valve Assembly Plug, lb-ft (Nm) ............... 28.9-36.1 (39.2-49.0)
Starter Motor Frame Mounting Flange Bolt, lb-ft (Nm) ............... 36.1-50.6 (49.0-68.6)
Alternator Pivot Mount Long Structural Bolt, lb-ft (Nm) ............... 21.7-28.9 (29.4-39.2)
Alternator Tension Adjuster Link Lock Bolt, lb-ft (Nm) ............... 14.5-18.0 (19.6-24.5)
Engine Mount Bracket To Cylinder Block Bolt, lb-ft (Nm) ............... 36.1-43.4 (49.0-58.8)
Fuel Filter Bracket Holding Chassis Bolt, lb-ft (Nm) ............... 14.5-18.0 (19.6-24.5)
Air Cleaner Bracket Shell Holding Bolt, lb-ft (Nm) ............... 14.5-18.0 (19.6-24.5)
Exhaust Pipe Counter Flange Attachment Nut, lb-ft (Nm) ............... 21.7-28.9 (29.4-39.2)
Fan Blade Assembly to Water Pump Hub Bolt, lb-ft (Nm) ............... 7.2-10.8 (9.8-14.7)
Oil Screen Pick-up Tube Bracket Bolt, lb-ft (Nm) ............... 14.5-18.0 (19.6-24.5)
Injection Pump Gear Retaining Drive Nut, lb-ft (Nm) ............... 28.9-36.1 (39.2-49.0)
Camshaft Gear Center Locking Attachment Bolt, lb-ft (Nm) ............... 57.8-65.0 (78.4-88.2)
Rear Oil Seal Retainer Plate Housing Bolt, lb-ft (Nm) ............... 14.5-18.0 (19.6-24.5)
Front Crankshaft Oil Seal Slinger Screw, lb-ft (Nm) ............... 5.1-7.2 (6.9-9.8)
Rocker Arm Adjusting Screw Jam Lock Nut, lb-ft (Nm) ............... 10.8-14.5 (14.7-19.6)
Breather Valve Cover Small Fitting Bolt, lb-ft (Nm) ............... 5.1-7.2 (6.9-9.8)
Fuel Feed Pump Lever Cam Drive Mounting Bolt, lb-ft (Nm) ............... 14.5-18.0 (19.6-24.5)
Governor Housing Cover Plate Rear Screw, lb-ft (Nm) ............... 5.1-7.2 (6.9-9.8)
Governor Tie Rod Access Hole Swivel Plug, lb-ft (Nm) ............... 7.2-10.8 (9.8-14.7)

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• Mitsubishi Engines Specs
  
• Mitsubishi K3E Specs
  
• Mitsubishi K3F Specs
  
• Mitsubishi K3G Specs
  
• Mitsubishi K3M Specs
  

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