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Caterpillar 3406 DITA Engine

The Caterpillar 3406 DITA (Direct Injection, Turbocharged, Aftercooled) is a legendary, heavy-duty industrial and marine diesel engine built for maximum reliability and structural longevity. Primarily utilizing mechanical systems (predating the fully electronic EUI systems found in the 3406E), this configuration is highly favored for its simplicity, ease of field tuning, and tolerance to varying fuel qualities. Its heavy-duty cast iron block and robust wet-sleeve cylinder liner design make it a preferred choice for long-haul trucks, marine propulsion, backup power generation, and demanding industrial applications.

The fuel system configuration employs a completely mechanical direct injection system. Fuel is pulled from the storage tank by a mechanical fuel transfer pump through a primary water separator and high-efficiency spin-on fuel filters. It is then fed into a high-pressure, multi-plunger mechanical fuel injection pump assembly. This injection pump is driven directly by the engine's front gear train and features an integrated hydra-mechanical governor to regulate fuel delivery based on RPM and load demands. Precise fuel charges are delivered through high-pressure steel lines to mechanical fuel injectors located in each cylinder head, which spray fuel under intense pressure directly into the combustion chambers. A fuel ratio control valve monitors boost pressure from the turbocharger to prevent over-fueling and excessive smoke production during rapid acceleration.

The lubrication system is a pressure-type design relying on a gear-driven oil pump that draws oil from the oil pan sump through a suction bell and pickup tube. Pressurized oil passes directly through an engine-mounted oil cooler and a full-flow fluid filter assembly before entering the main oil manifold inside the cylinder block. Built-in bypass valves ensure uninterrupted lubrication by routing oil past the cooler or filter if blockage or high oil viscosity occurs during cold starts. The main manifold distributes dedicated oil passages to the crankshaft main bearings, connecting rod journals, camshaft bearings, piston cooling jets, valve lifter bores, and the upper rocker arm mechanisms, with a separate high-pressure external feed and return system supplying the turbocharger bearings.

The cooling architecture uses a pressurized, closed-loop layout forced by a gear-driven centrifugal jacket water pump mounted to the front of the engine block. The pump moves coolant through the engine block channels, cylinder head jacket passages, oil cooler, and the core of the air-to-air or jacket-water aftercooler (JWAC). System temperature regulation is handled mechanically via dual heavy-duty thermostats housed at the front upper outlet. When the engine is cold, the thermostats remain closed, routing coolant through a dedicated bypass pipe back to the water pump intake to ensure rapid warm-up and maintain adequate pump head pressure to prevent cavitation. Once normal operating temperature is achieved, the thermostats fully open to flow coolant out to the external radiator or marine raw-water heat exchanger.

General Technical Data

Engine Specifications

Engine Model ............... Caterpillar 3406 DITA
Engine Type ............... 4-cycle inline 6-cylinder direct injection liquid-cooled diesel
Number of Cylinders ............... 6
Cylinder Arrangement ............... In-line
Engine Bore, in (mm) ............... 5.39 (137.0)
Engine Stroke, in (mm) ............... 6.49 (165.0)
Displacement, cu.in (L) ............... 893 (14.6)
Rated Engine Power, hp (kW) ............... 290-465 (217-347)
Rated Engine Speed, rpm ............... 1800-2100
Peak Torque ............... 1690-2160 Nm (1250-1600 lb-ft) at 1200-1400 rpm
Idle Speed ............... 600-650 rpm
Aspiration Type ............... Turbocharged and Air-to-Air Aftercooled (ATAAC)
Operating Speed ............... 2000 rpm
Compression Ratio ............... 14.5:1
Firing Order ............... 1-5-3-6-2-4
Crankshaft Type ............... Forged steel
Piston Type ............... Cast-aluminum alloy
Con Rod Type ............... Forged steel
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 ............... Gear-driven, centrifugal
Air Cleaner Type ............... Dry dual-stage
Starting System ............... Electric Starter
Electrical System ............... 12V or 24V
Alternator Rating, Amps ............... 45-100

Fuel System

Fuel System ............... Direct injection
Injection Pump Type ............... Rotary
Fuel System Control ............... Mechanical
Governor Type ............... Mechanical
Fuel Injector Type ............... Multi-hole
Fuel Type ............... Diesel Fuel

Dimensions and Weight

Overall Length, in (mm) ............... 65.4 (1660)
Overall Width, in (mm) ............... 35.7 (905)
Overall Height, in (mm) ............... 52.6 (1335)
Dry Weight, lbs (kg) ............... 2860-3080 (1300-1400)

Maintenance Data

Service Information

Thermostat begins opening ............... 82C (180F)
Thermostat fully open ............... 99C (210F)
Cooling system pressure ............... 70-100 kPa (10-15 psi)
Operating oil pressure ............... 275-410 kPa (40-60 psi)
Idle oil pressure ............... 140-275 kPa (15-30 psi)
Intake Valve Clearance, in (mm) ............... 0.015-0.017 (0.38-0.43)
Exhaust Valve Clearance, in (mm) ............... 0.025-0.030 (0.64-0.76)

Engine Oil and Coolant

Engine Oil Type .................. SAE 10W-30, 15W-40
API Service Classifications ......................... CH-4 or CI-4
Engine Oil Capacity, qts (L) .................. 36.7-44.1 (35.0-42.0)
Coolant Capacity, qts (L) ............... 31.5-39.9 (30.0-38.0)

Service Intervals

Change oil and filter ............... Every 250 hours
Replace fuel filters ............... Every 500 hours
Inspect air filter ............... Every 100 hours
Change coolant ............... Every 2 years
Valve-lash adjustment ............... Every 1000 hours
Injector inspection ............... Every 1000-1500 hours
Compression test ............... Every 2000 hours
Drain water separator ............... As required
Belt inspection ............... As required

Service Specifications

Cylinder Bore Inside Diameter, in (mm) ................ 5.400-5.402 (137.16-137.21)
Crankshaft Journal Outside Diameter, in (mm) ................ 4.7500-4.7512 (120.650-120.680)
Crank Pin Outside Diameter, in (mm) ................ 3.5000-3.5012 (88.900-88.930)
Crankshaft End Play, in (mm) ................ 0.005-0.021 (0.13-0.53)
Intake Valve Stem Outside Diameter, in (mm) ................ 0.3715-0.3725 (9.436-9.462)
Exhaust Valve Stem Outside Diameter, in (mm) ................ 0.3705-0.3715 (9.411-9.436)
Intake Valve Guide Inside Diameter (Installed), in (mm) ................ 0.3735-0.3745 (9.487-9.512)
Exhaust Valve Guide Inside Diameter (Installed), in (mm) ................ 0.3735-0.3745 (9.487-9.512)
Intake Valve Stem to Guide Clearance, in (mm) ................ 0.0010-0.0030 (0.025-0.076)
Exhaust Valve Stem to Guide Clearance, in (mm) ................ 0.0020-0.0040 (0.051-0.102)
Intake Valve Spring Free Length, in (mm) ................ 2.49 (63.2)
Exhaust Valve Spring Free Length, in (mm) ................ 2.49 (63.2)
Intake Cam Height, in (mm) ................ 2.285-2.297 (58.04-58.34)
Exhaust Cam Height, in (mm) ................ 2.245-2.257 (57.02-57.32)
Piston Pin Outside Diameter, in (mm) ................ 2.0000-2.0004 (50.800-50.810)
Piston Pin to Piston Bore Clearance, in (mm) ................ 0.0004-0.0012 (0.010-0.030)
Top Ring Side Clearance, in (mm) ................ 0.0035-0.0055 (0.089-0.140)
Second Ring Side Clearance, in (mm) ................ 0.0025-0.0045 (0.064-0.114)
Oil Ring Side Clearance, in (mm) ................ 0.0015-0.0035 (0.038-0.089)
Top Ring End Gap, in (mm) ................ 0.0200-0.0340 (0.508-0.864)
Second Ring End Gap, in (mm) ................ 0.0180-0.0300 (0.457-0.762)
Oil Ring End Gap, in (mm) ................ 0.0150-0.0270 (0.381-0.686)

Tightening Torque Specs

Cylinder head bolts ................ 270-310 Nm (199-229 lb-ft)
Main bearing caps ................ 400-450 Nm (295-332 lb-ft)
Connecting rods ................ 155-175 Nm (114-129 lb-ft)
Flywheel bolts ................ 380-420 Nm (280-310 lb-ft)
Crankshaft pulley bolt ................ 450-500 Nm (332-369 lb-ft)
Oil drain plug ................ 50-70 Nm (37-52 lb-ft)
Injector hold-downs ................ 35-45 Nm (26-33 lb-ft)

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• Caterpillar Engines Specs
  
• Cat 3306B Specs
  
• Cat 3306C Specs
  
• Cat 3306TA Specs
  
• Cat 3406A Specs
  
• Cat 3406B Specs
  

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