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Caterpillar 3408 Engine

The Caterpillar 3408 is a heavy-duty, 18.0-liter (1,099 cubic inches) internal combustion V8 diesel engine configured in a 90-degree layout. Introduced in the 1970s as a high-power variant alongside the inline-six 3406, this engine platform earned a reputation for exceptional low-end torque, mechanical durability, and long operational life. It features a robust cast-iron block utilizing replaceable wet cylinder liners. This model is widely deployed across demanding sectors including marine vessels, oil and gas extraction, power generation, mining, and heavy industrial machinery. The cylinder bore diameter measures 137 mm (5.40 inches). The piston stroke length measures 152 mm (6.00 inches).

Fuel delivery utilizes a mechanically governed direct-injection system. A positive-displacement mechanical fuel transfer pump draws fuel from source tanks through a primary water separator/filter and forces it into dual secondary filtration elements. Pressurized fuel routes directly into an internal fuel injection pump housing. Individual high-pressure mechanical injection lines route from the pump element to dedicated fuel injection valves located inside specialized direct-injection adapters inside the cylinder head assemblies. An integrated manual priming pump is standard on the primary assembly to evacuate air bubbles from the fuel lines during servicing operations.

Engine components are protected via a full-pressure internal lubrication system powered by a dedicated oil pump. The circuit incorporates top-mounted crankcase breathers, integrated oil coolers, and spin-on secondary or cartridge filtration units. Fluid capacities vary by oil pan design and application depth. Thermal regulation is managed by a closed-loop jacket water circuit driven by a gear-driven centrifugal water pump. The assembly incorporates a standard thermostat housing assembly regulating operational flow across a temperature range of 180F to 208F (82C to 99C).

General Technical Data

Engine Specifications

Engine Model ............... Caterpillar 3408
Engine Type ............... 4-cycle 8-cylinder V-block direct injection liquid-cooled diesel
Number of Cylinders ...............
Cylinder Arrangement ............... V-type
Engine Bore, in (mm) ............... 5.39 (137.0)
Engine Stroke, in (mm) ............... 5.98 (152.0)
Displacement, cu.in (L) ............... 1099 (18.0)
Rated Engine Power (Generator), hp (kW) ............... 300-600 (220-450)
Rated Engine Power (Marine), hp (kW) ............... 500-800 (370-590)
Rated Engine Speed, rpm ............... 2100-2300
Aspiration Type ............... Turbocharged or Turbocharged and Aftercooled
Operating Speed ............... 2300 rpm
Compression Ratio ............... 14.1:1
Firing Order ............... 1-8-7-5-4-3-6-2
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 ............... 130-200

Fuel System

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

Dimensions and Weight

Overall Length, in (mm) ............... 68-69 (1740-1755)
Overall Width, in (mm) ............... 52-61.5 (1310-1565)
Overall Height, in (mm) ............... 60-69 (1540-1760)
Dry Weight, lbs (kg) ............... 3800-4000 (1730-1820)

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 ......................... CD, CE, or CF-4
Engine Oil Capacity, qts (L) .................. 42.0-48.3 (40.0-46.0)
Coolant Capacity, qts (L) ............... 52.5-63.0 (50.0-60.0)

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 3406C Specs
  
• Cat 3406E Specs
  
• Cat 3408C Specs
  
• Cat 3408E Specs
  

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