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Caterpillar 3304B Engine

The Caterpillar 3304B is a heavy-duty, inline 4-cylinder diesel engine representing the refined evolution of the legendary 3300-series platform. Engineered for severe-duty applications, it is widely utilized in medium track-type tractors (such as the D4H and D5M), wheel loaders, industrial power units, and marine auxiliary gensets. Unlike its 3200-series counterparts, the 3304B features replaceable wet cylinder liners, making it infinitely rebuildable in the field. It is a true mechanical workhorse, prized by technicians for its extreme durability, simple heavy-duty architecture, and exceptional torque-rise characteristics.

Fuel Injection Pump: Features the robust Cat New Scroll Fuel System (NSFS) or sleeve-metered system depending on production year, mounted on the left side of the engine. Fuel Transfer: A mechanical, gear-driven or piston-type transfer pump delivers fuel from the tank to the injection gallery at low pressure. Injectors: Employs direct injection utilizing capsule-type fuel nozzles fed by heavy-walled, external high-pressure steel lines. Governor: Mechanical flyweight governor or optional Hydra-Mechanical governor integrated onto the rear of the fuel injection pump housing.

Lubrication System: Full-pressure system driven by a gear-type oil pump mounted to the front timing gear train. Oil Filtration and Cooling: Includes a spin-on, full-flow filter assembly mated to an external, multi-plate oil cooler to maintain viscosity under continuous heavy loads. Service: Oil pressure must be verified at the main oil gallery. Normal hot operating pressure should register between 35 and 65 psi (240 to 450 kPa) at rated speed.

Cooling System: Liquid-cooled, closed-circuit configuration utilizing a high-capacity, gear-driven centrifugal water pump. Flow and Regulation: Coolant flows through the engine block, directly surrounding the wet liners, passes into the cylinder head, and is regulated by a single heavy-duty thermostat. Maintenance: Strict adherence to Supplemental Coolant Additives (SCAs) or extended-life coolant is mandatory to prevent cavitation erosion on the external walls of the wet cylinder liners.

General Technical Data

Engine Specifications

Engine Model ............... Caterpillar 3304B
Engine Type ............... 4-cycle inline 4-cylinder direct injection liquid-cooled diesel
Number of Cylinders ............... 4
Cylinder Arrangement ............... In-line
Engine Bore, in (mm) ............... 4.76 (121.0)
Engine Stroke, in (mm) ............... 6.00 (152.0)
Displacement, cu.in (L) ............... 425 (7.0)
Rated Engine Power (Industrial), hp (kW) ............... 75-140 (52-104)
Rated Engine Power (Marine), hp (kW) ............... 85-165 (63-123)
Rated Engine Speed, rpm ............... 1800-2200
Peak Torque ............... 350-550 Nm (258-406 lb-ft) at 1300-1600 rpm
Idle Speed ............... 650-750 rpm
Aspiration Type ............... Naturally Aspirated or Turbocharged
Operating Speed ............... 2000 rpm
Compression Ratio ............... 16.0:1 or 15.0:1
Firing Order ............... 1-3-4-2
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 ............... Belt-driven, centrifugal
Air Cleaner Type ............... Dry dual-stage
Starting System ............... Electric Starter
Electrical System ............... 12V or 24V
Alternator Rating, Amps ............... 35-70

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) ............... 37-43 (950-1100)
Overall Width, in (mm) ............... 29-33 (750-850)
Overall Height, in (mm) ............... 37-45 (950-1150)
Dry Weight, lbs (kg) ............... 1650-1870 (750-850)

Maintenance Data

Service Information

Thermostat begins opening ............... 82C (180F)
Thermostat fully open ............... 95C (203F)
Cooling system pressure ............... 70-100 kPa (10-15 psi)
Operating oil pressure ............... 300-450 kPa (44-65 psi)
Idle oil pressure ............... 100-150 kPa (15-22 psi)
Intake Valve Clearance, in (mm) ............... 0.015-0.017 (0.38-0.43)
Exhaust Valve Clearance, in (mm) ............... 0.025-0.027 (0.64-0.69)

Engine Oil and Coolant

Engine Oil Type .................. SAE 10W-30, 15W-40
API Service Classifications ......................... CI-4 or higher
Engine Oil Capacity, qts (L) .................. 20.0-23.1 (19.0-22.0)
Coolant Capacity, qts (L) ............... 13.6-16.8 (13.0-16.0)

Service Intervals

Change oil and filter ............... Every 250 hours
Replace fuel filters ............... Every 300 hours
Inspect air filter ............... Every 50 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) ................ 4.750-4.752 (120.65-120.70)
Crankshaft Journal Outside Diameter, in (mm) ................ 3.4990-3.5000 (88.875-88.900)
Crank Pin Outside Diameter, in (mm) ................ 2.9987-3.0003 (76.167-76.208)
Crankshaft End Play, in (mm) ................ 0.007-0.025 (0.17-0.63)
Intake Valve Stem Outside Diameter, in (mm) ................ 0.3717-0.3725 (9.441-9.462)
Exhaust Valve Stem Outside Diameter, in (mm) ................ 0.3705-0.3713 (9.411-9.431)
Intake Valve Guide Inside Diameter (Installed), in (mm) ................ 0.3734-0.3744 (9.484-9.510)
Exhaust Valve Guide Inside Diameter (Installed), in (mm) ................ 0.3734-0.3744 (9.484-9.510)
Intake Valve Stem to Guide Clearance, in (mm) ................ 0.0009-0.0027 (0.022-0.069)
Exhaust Valve Stem to Guide Clearance, in (mm) ................ 0.0021-0.0039 (0.053-0.099)
Intake Valve Spring Free Length, in (mm) ................ 2.47 (62.7)
Exhaust Valve Spring Free Length, in (mm) ................ 2.47 (62.7)
Intake Cam Height, in (mm) ................ 1.844-1.856 (46.84-47.14)
Exhaust Cam Height, in (mm) ................ 1.844-1.856 (46.84-47.14)
Piston Pin Outside Diameter, in (mm) ................ 1.5011-1.5013 (38.128-38.133)
Piston Pin to Piston Bore Clearance, in (mm) ................ 0.0002-0.0008 (0.005-0.020)
Top Ring Side Clearance, in (mm) ................ 0.0031-0.0051 (0.079-0.130)
Second Ring Side Clearance, in (mm) ................ 0.0024-0.0043 (0.061-0.109)
Oil Ring Side Clearance, in (mm) ................ 0.0016-0.0035 (0.041-0.089)
Top Ring End Gap, in (mm) ................ 0.0170-0.0320 (0.432-0.813)
Second Ring End Gap, in (mm) ................ 0.0150-0.0270 (0.381-0.686)
Oil Ring End Gap, in (mm) ................ 0.0100-0.0220 (0.254-0.559)

Tightening Torque Specs

Cylinder head bolts ............... 250-300 Nm (184-221 lb-ft)
Main-bearing caps ............... 300-350 Nm (221-258 lb-ft)
Connecting-rod bolts ............... 110-130 Nm (81-96 lb-ft)
Flywheel bolts ............... 200-240 Nm (148-177 lb-ft)
Crankshaft pulley bolt ............... 350-450 Nm (258-332 lb-ft)
Oil drain plug ............... 40-55 Nm (30-41 lb-ft)
Injector hold-downs ............... 25-30 Nm (18-22 lb-ft)

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• Caterpillar Engines Specs
  
• Cat 3204 Specs
  
• Cat 3208 Specs
  
• Cat 3208T Specs
  
• Cat 3208TA Specs
  
• Cat 3304 Specs
  
• Cat 3306 DITA Specs
  

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