________________________________________________________________________________

Mitsubishi K4C Engine

The Mitsubishi K4C is a vertical, water-cooled, 4-stroke, 4-cylinder inline diesel engine engineered for reliability, thermal stability, and a high power-to-weight ratio. It is widely deployed across standard industrial, agricultural, and construction equipment—including compact tractors (such as the Mitsubishi D2350), mini-excavators, loaders, generators, and small marine crafts. Built on a rigid cast-iron block design, the K4C is highly regarded for its minimal footprint and operational dependability under high cyclic loads.

The engine utilizes a vertical Overhead Valve (OHV) arrangement driven by a gear-train-actuated camshaft located within the cylinder block. It features two valves per cylinder (one intake and one exhaust), operating via pushrods and rocker arm assemblies to ensure consistent volumetric efficiency. Bore: 70 mm. Stroke: 78 mm. Total Displacement: 1.200 Liters (1200 cc).

Lubrication is managed via a forced-pressure feed system powered by a trochoid oil pump driven directly by the crankshaft. Engine oil is drawn through an inlet screen from the wet oil pan, passed through a full-flow spin-on cartridge oil filter, and routed into the main oil gallery. Rocker arms, main bearings, and connecting rod bearings are pressure lubricated, while the cylinder walls and wrist pins are lubricated via splash feed.

The engine uses a forced-circulation water cooling system. An engine-driven centrifugal water pump circulates coolant through the cylinder block water jackets and cylinder head passages. A pellet-type wax thermostat controls routing, diverting flow directly through a bypass loop during warm-up and opening into a full radiator circuit once the nominal operating temperature is reached.

The fuel system uses an indirect injection (IDI) design utilizing a combustion pre-chamber to ensure quiet ignition and thorough atomization. Fuel is drawn through a spin-on sedimenter/fuel filter assembly by a mechanical diaphragm feed pump. It is then supplied to an inline Bosch-type multi-plunger fuel injection pump driven by the engine timing gear train. High-pressure fuel lines deliver metered fuel to throttle-type injection nozzles, which spray directly into the pre-combustion chamber. Engine speed regulation is sustained by a mechanical all-speed governor integrated into the injection pump housing.

General Technical Data

Engine Specifications

Engine Model ............... Mitsubishi K4C
Engine Type ............... 4-cycle vertical inline 4-cylinder liquid-cooled diesel
Number of Cylinders ............... 4
Cylinder Arrangement ............... In-line vertical
Engine Bore, in (mm) ............... 2.76 (70.0)
Engine Stroke, in (mm) ............... 3.07 (78.0)
Displacement, cu.in (L) ............... 73.23 (1.200)
Rated Engine Power, hp (kW) ............... 24.0-30.0 (17.9-22.4)
Rated Engine Speed, rpm ............... 2500-3000
Peak Torque ............... 53.1-64.2 lb-ft (72.0-87.0 Nm) at 1800-2200 rpm
Low Idle Speed, rpm ............... 750-850
High Idle Speed, rpm ............... 2700-3200
Aspiration Type ............... Naturally aspirated
Compression Ratio ............... 22.0:1-23.0:1
Firing Order ............... 1-3-4-2
Combustion System ............... Indirect injection
Valve Mechanism ............... Overhead valve (OHV)
Number of Valves per Cylinder ............... 2 (1 intake, 1 exhaust)
Total Number of Valves ............... 8
Crankshaft Rotation Direction ............... Counterclockwise from flywheel side
Cylinder Block Material ............... High-strength cast iron alloy
Cylinder Head Material ............... High-strength cast iron alloy
Piston Material ............... Aluminum alloy with thermal slot inserts
Lubrication System ............... Full-pressure forced lubrication by oil pump
Oil Pump Type ............... Trochoid type gear pump
Oil Filter Type ............... Full-flow spin-on cartridge elements
Cooling System ............... Forced circulation liquid cooling with thermostat
Water Pump Type ............... Belt-driven centrifugal impeller pump
Air Cleaner Type ............... Dry dual element or oil bath assembly
Starting System ............... Electric starter motor actuation
Electrical System, V ............... 12
Alternator Capacity, A ............... 15-35

Fuel System

Fuel Injection Pump Type ............... Bosch Type M or Type P mini in-line pump
Fuel Injection Pump Drive ............... Gear-driven from camshaft gear train
Governor Type ............... Mechanical centrifugal all-speed governor
Fuel Injection Nozzle Type ............... Throttle or pintle design nozzle
Fuel Injection Nozzle Holder ............... Bosch flange or screw-in assembly
Fuel Injection Pressure, psi (bar) ............... 1707-1849 (118.0-127.5)
Fuel Injection Timing ............... 16-20 deg BTDC
Fuel Feed Pump Type ............... Mechanical diaphragm displacement pump
Fuel Filter Type ............... Cartridge spin-on element with water separator
Fuel Line Diameter Intake, in (mm) ............... 0.31 (8.0)
Fuel Return Line Diameter, in (mm) ............... 0.24 (6.0)
Recommended Fuel Grade ............... Ultra-low sulfur diesel ASTM D975 No. 2-D
Injection Pump Plating Diameter, in (mm) ............... 0.20-0.24 (5.0-6.0)
Injection Pump Stroke, in (mm) ............... 0.24-0.28 (6.0-7.0)
Nozzle Valve Seat Angle ............... 59-60 deg
Nozzle Needle Valve Diameter, in (mm) ............... 0.16 (4.0)
Nozzle Lift, in (mm) ............... 0.012-0.016 (0.30-0.40)

Dimensions and Weight

Overall Length, in (mm) ............... 20.8-22.4 (530-570)
Overall Width, in (mm) ............... 16.5-18.1 (420-460)
Overall Height, in (mm) ............... 22.1-24.4 (560-620)
Dry Weight, lbs (kg) ............... 243-276 (110-125)
Wet Weight, lbs (kg) ............... 265-298 (120-135)

Maintenance Data

Service Information

Compression Pressure, Lower Limit, psi (bar) ............... 355-384 (24.5-26.5)
Compression Pressure, Standard, psi (bar) ............... 426-455 (29.4-31.4)
Compression Pressure Between Cylinders, psi (bar) ............... 28.4-42.6 (2.0-3.0)
Oil Pressure at Low Idle Speed, psi (bar) ............... 7.1-14.2 (0.5-1.0)
Oil Pressure at Rated Speed, psi (bar) ............... 42.7-71.1 (3.0-5.0)
Oil Pressure Relief Valve, psi (bar) ............... 56.9-71.1 (3.9-4.9)
Radiator Cap Pressure Rating, psi (bar) ............... 12.8 (0.9)
Maximum Allowable Coolant Temperature, F (C) ............... 212 (100)
Normal Coolant Temperature Range, F (C) ............... 167-194 (75-90)
Thermostat Opening Temperature ............... 160-170 F (71-77 C)
Thermostat Full Open Temperature ............... 185-195 F (85-91 C)
Fan Belt Deflection, Standard, in (mm) ............... 0.28-0.47 (7.0-12.0)
Intake Valve Lash, Cold, in (mm) ............... 0.010 (0.25)
Exhaust Valve Lash, Cold, in (mm) ............... 0.010 (0.25)

Engine Oil and Coolant

Engine Oil Type .................. SAE 30W, SAE 10W-30, or 15W-40
API Service Classifications ......................... CD, CE, CF, CF-4, or CG-4
Engine Oil Capacity with Filter, qt (L) ............... 4.23-4.76 (4.0-4.5)
Engine Oil Capacity without Filter, qt (L) ............... 3.70-4.23 (3.5-4.0)
Engine Oil Pan, Upper Level, qt (L) ............... 4.23 (4.0)
Engine Oil Pan, Lower Level, qt (L) ............... 2.64 (2.5)
Coolant Capacity, Engine Only, qt (L) ............... 2.11-2.64 (2.0-2.5)

Service Intervals

Change oil and filter ............... Every 150 hours
Inspect air cleaner ............... Every 50 hours
Replace air cleaner ............... Every 500 hours
Replace fuel filter ............... Every 250 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 Inside Diameter, in (mm) ............... 2.7559-2.7567 (70.000-70.020)
Cylinder Bore Maximum Out of Round, in (mm) ............... 0.0079 (0.200)
Cylinder Head Surface Flatness Distortion, in (mm) ............... 0.002 (0.05)
Cylinder Block Top Surface Flatness Distortion, in (mm) ............... 0.002 (0.05)
Connecting Rod Small End Bushing I.D, in (mm) ............... 0.7876-0.7882 (20.005-20.020)
Crankshaft Main Journal Diameter, in (mm) ............... 1.9681-1.9685 (49.990-50.000)
Crankshaft Main Journal Taper, in (mm) ............... 0.0004 (0.010)
Main Bearing Oil Clearance, in (mm) ............... 0.0014-0.0031 (0.035-0.080)
Main Bearing Shell Thickness, in (mm) ............... 0.059 (1.50)
Crankpin Journal Diameter, in (mm) ............... 1.6531-1.6535 (41.990-42.000)
Connecting Rod Big End Bearing Clearance, in (mm) ............... 0.0012-0.0028 (0.030-0.070)
Connecting Rod Center to Center Length, in (mm) ............... 4.53 (115.0)
Crankshaft End Play, in (mm) ............... 0.0020-0.0071 (0.050-0.180)
Piston Outside Diameter, in (mm) ............... 2.7528-2.7535 (69.920-69.940)
Piston to Cylinder Bore Clearance, in (mm) ............... 0.0024-0.0039 (0.060-0.100)
Piston Pin Bore Inside Diameter, in (mm) ............... 0.7874-0.7877 (20.000-20.008)
Piston Pin Outside Diameter, in (mm) ............... 0.7871-0.7874 (19.993-20.000)
Piston Pin to Piston Pin Bore Clearance, in (mm) ............... 0.0000-0.0006 (0.000-0.015)
Piston Pin to Con Rod Small End Bushing Clearance, in (mm) ............... 0.0002-0.0011 (0.005-0.027)
Top Ring Groove Width, in (mm) ............... 0.0803-0.0811 (2.040-2.060)
Second Ring Groove Width, in (mm) ............... 0.0795-0.0803 (2.020-2.040)
Oil Ring Groove Width, in (mm) ............... 0.1583-0.1591 (4.020-4.040)
Top Ring Groove Side Clearance, in (mm) ............... 0.0024-0.0039 (0.060-0.100)
Second Ring Groove Side Clearance, in (mm) ............... 0.0016-0.0031 (0.040-0.080)
Oil Ring Groove Side Clearance, in (mm) ............... 0.0008-0.0024 (0.020-0.060)
Top Ring End Gap, in (mm) ............... 0.0059-0.0118 (0.150-0.300)
Second Ring End Gap, in (mm) ............... 0.0059-0.0118 (0.150-0.300)
Oil Ring End Gap, in (mm) ............... 0.0039-0.0118 (0.100-0.300)
Intake Valve Stem Outside Diameter, in (mm) ............... 0.2583-0.2591 (6.560-6.580)
Exhaust Valve Stem Outside Diameter, in (mm) ............... 0.2567-0.2575 (6.520-6.540)
Intake Valve Guide Inside Diameter, in (mm) ............... 0.2598-0.2607 (6.600-6.622)
Exhaust Valve Guide Inside Diameter, in (mm) ............... 0.2598-0.2607 (6.600-6.622)
Intake Valve Stem to Guide Clearance, in (mm) ............... 0.0008-0.0024 (0.020-0.062)
Exhaust Valve Stem to Guide Clearance, in (mm) ............... 0.0024-0.0039 (0.060-0.102)
Valve Face Angle, deg ............... 45
Valve Seat Angle, deg ............... 45
Valve Seat Width, in (mm) ............... 0.0472-0.0630 (1.20-1.60)
Valve Spring Free Length, in (mm) ............... 1.4961 (38.00)
Camshaft Journal Outside Diameter (Front), in (mm) ............... 1.5728-1.5736 (39.950-39.970)
Camshaft Journal Outside Diameter (Middle), in (mm) ............... 1.5335-1.5343 (38.950-38.970)
Camshaft Journal Outside Diameter (Rear), in (mm) ............... 1.4941-1.4949 (37.950-37.970)
Camshaft Bushing Inside Diameter (Front), in (mm) ............... 1.5748-1.5760 (40.000-40.030)
Camshaft Housing Bore Inside Diameter (Middle), in (mm) ............... 1.5354-1.5366 (39.000-39.030)
Camshaft Housing Bore Inside Diameter (Rear), in (mm) ............... 1.4961-1.4972 (38.000-38.030)
Camshaft Journal to Bushing Oil Clearance (Front), in (mm) ............... 0.0012-0.0031 (0.030-0.080)
Camshaft Journal to Bore Oil Clearance (Middle), in (mm) ............... 0.0012-0.0031 (0.030-0.080)
Camshaft Journal to Bore Oil Clearance (Rear), in (mm) ............... 0.0012-0.0031 (0.030-0.080)
Cam Lobe Height (Intake), in (mm) ............... 1.3268-1.3287 (33.700-33.750)
Cam Lobe Height (Exhaust), in (mm) ............... 1.3268-1.3287 (33.700-33.750)
Camshaft End Play, in (mm) ............... 0.0020-0.0059 (0.050-0.150)
Rocker Arm Shaft Outside Diameter, in (mm) ............... 0.4713-0.4720 (11.970-11.990)
Rocker Arm Bushing Inside Diameter, in (mm) ............... 0.4724-0.4736 (12.000-12.030)
Rocker Arm Bushing to Shaft Oil Clearance, in (mm) ............... 0.0004-0.0024 (0.010-0.060)
Tappet Lifter Body Outside Diameter, in (mm) ............... 0.7469-0.7476 (18.970-18.990)
Tappet Lifter Block Bore Inside Diameter, in (mm) ............... 0.7480-0.7492 (19.000-19.030)
Tappet to Cylinder Block Bore Clearance, in (mm) ............... 0.0004-0.0024 (0.010-0.060)
Idle Gear Shaft Outside Diameter, in (mm) ............... 0.7862-0.7870 (19.970-19.990)
Idle Gear Bushing Inside Diameter, in (mm) ............... 0.7874-0.7886 (20.000-20.030)
Idle Gear Bushing to Shaft Oil Clearance, in (mm) ............... 0.0004-0.0024 (0.010-0.060)

Tightening Torques

Cylinder Head Bolts ............... 54.2-57.8 lb-ft (73.5-78.5 Nm)
Connecting Rod Cap Nuts ............... 23.1-25.3 lb-ft (31.4-34.3 Nm)
Main Bearing Cap Bolts ............... 36.2-39.8 lb-ft (49.0-54.0 Nm)
Flywheel Mounting Bolts ............... 57.8-61.4 lb-ft (78.5-83.3 Nm)
Crankshaft Pulley Center Nut ............... 72.3-79.6 lb-ft (98.0-107.9 Nm)
Camshaft Thrust Plate ............... 10.8-14.5 lb-ft (14.7-19.6 Nm)
Camshaft Timing Gear Bolt ............... 43.4-50.6 lb-ft (58.8-68.6 Nm)
Rocker Shaft Bracket Mounting Bolts ............... 10.8-14.5 lb-ft (14.7-19.6 Nm)
Rocker Arm Adjusting Screw ............... 8.7-12.3 lb-ft (11.8-16.7 Nm)
Timing Gear Case Cover M6 Bolts ............... 5.8-7.2 lb-ft (7.8-9.8 Nm)
Timing Gear Case Cover M8 Bolts ............... 10.8-14.5 lb-ft (14.7-19.6 Nm)
Oil Pan Mounting Bolts ............... 4.3-5.8 lb-ft (5.9-7.8 Nm)
Oil Pan Drain Plug ............... 25.3-32.5 lb-ft (34.3-44.1 Nm)
Fuel Injection Pump Mounting Bolts ............... 10.8-14.5 lb-ft (14.7-19.6 Nm)
Fuel Injection Pump Drive Gear Nut ............... 28.9-36.2 lb-ft (39.2-49.0 Nm)
Fuel Injection Nozzle to Head Retainer Nut ............... 36.2-43.4 lb-ft (49.0-58.8 Nm)
Fuel High Pressure Line Union Nuts ............... 18.1-21.7 lb-ft (24.5-29.4 Nm)
Fuel Return Pipe Line Bleed Nut ............... 14.5-18.1 lb-ft (19.6-24.5 Nm)
Glow Plug Terminal Nuts ............... 0.7-1.1 lb-ft (1.0-1.5 Nm)
Glow Plug Body ............... 10.8-14.5 lb-ft (14.7-19.6 Nm)
Water Pump Mounting Bolts ............... 10.8-14.5 lb-ft (14.7-19.6 Nm)
Thermostat Housing Cover Bolts ............... 10.8-14.5 lb-ft (14.7-19.6 Nm)
Intake Manifold Mounting Bolts ............... 10.8-14.5 lb-ft (14.7-19.6 Nm)
Exhaust Manifold Mounting Nuts ............... 14.5-18.1 lb-ft (19.6-24.5 Nm)
Oil Pressure Switch Sensor Unit ............... 8.7-12.3 lb-ft (11.8-16.7 Nm)
Water Temperature Sender Sensor Unit ............... 14.5-18.1 lb-ft (19.6-24.5 Nm)
Alternator Pivot Support Long Bolt ............... 25.3-32.5 lb-ft (34.3-44.1 Nm)
Alternator Adjusting Brace Lock Strap Boltt ............... 10.8-14.5 lb-ft (14.7-19.6 Nm)
Starter Motor Mounting Bolts ............... 28.9-36.2 lb-ft (39.2-49.0 Nm)
Flywheel Housing Backing Plate Mounting Bolts ............... 36.2-43.4 lb-ft (49.0-58.8 Nm)
Oil Pump Assembly Retention Screws ............... 5.8-7.2 lb-ft (7.8-9.8 Nm)
Breather Valve Cover Plate Screws ............... 2.2-3.6 lb-ft (3.0-4.9 Nm)
Front Crankshaft Oil Seal Retaining Bolts ............... 4.3-5.8 lb-ft (5.9-7.8 Nm)
Rear Crankshaft Oil Seal Retaining Bolts ............... 10.8-14.5 lb-ft (14.7-19.6 Nm)
Fuel Filter Bracket Support Mounting Bolts ............... 14.5-18.1 lb-ft (19.6-24.5 Nm)
Fan Blade Assembly Retention Screws ............... 5.8-7.2 lb-ft (7.8-9.8 Nm)

________________________________________________________________________________________

• Mitsubishi Engines Specs
  
• Mitsubishi K4D Specs
  
• Mitsubishi K4E Specs
  
• Mitsubishi K4F Specs
  
• Mitsubishi K4M Specs
  
• Mitsubishi K4N Specs
  

________________________________________________________________________________

________________________________________________________________________________________

_______________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________