Cat 3304 Specifications
| Engine Model: Caterpillar 3304 |
| Engine Type: 4-cycle inline 4-cylinder direct injection liquid-cooled diesel |
| Total Displacement: 425 cu.in (7.0 L) |
| Rated Engine Power: 70-140 Hp (52-104 kW) at 2100 rpm |
| Aspiration Type: Naturally aspirated or turbocharged |
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The Caterpillar 3304 is a mid-displacement,
mechanically controlled, four-cylinder diesel engine widely used in
construction, agricultural, industrial, and generator-set applications.
As part of the CAT 3300 engine family, the 3304 earned global
recognition for its legendary reliability, simple mechanical design,
long service life, and low operating cost. Its robust cast-iron block,
mechanical direct-injection fuel system, and durable rotating assembly
allow it to operate reliably in harsh environments such as mining, heavy
construction, agricultural fields, and remote industrial sites.
The engine is available in naturally aspirated (3304 NA), turbocharged
(3304T), and turbo-aftercooled (3304TA) configurations, providing
flexibility for various work environments. Because of its
straightforward design and long-term rebuildability, the 3304 remains
popular in older CAT equipment, including wheel loaders, excavators,
generators, graders, and compressor systems.
The Caterpillar 3304 is a four-stroke, water-cooled, inline
four-cylinder diesel engine. Total displacement is approximately 7.0
liters (425 cubic inches). Bore is 121 mm (4.76 in), stroke is 152 mm
(6.00 in). The long-stroke layout provides excellent low-RPM torque and
high fuel efficiency.
Compression ratio varies by configuration:
— Naturally aspirated: approx. 16.0:1
— Turbocharged: approx. 15.0:1
Power ratings vary widely:
— Industrial: 70–140 hp (52–104 kW) @ 1,800–2,200 rpm
— Construction machines: 85–140 hp (63–104 kW)
— Generator sets: 40–120 kW @ 1,500–1,800 rpm
Peak torque: 350–550 Nm (258–406 lb-ft) @ 1,300–1,600 rpm. Idle speed:
typically 650–750 rpm. Governed speed: 1,800–2,200 rpm. Firing order:
1-3-4-2.
The crankshaft is forged steel with five main bearings. Pistons are cast
aluminum or steel-crown composite depending on configuration. Connecting
rods are forged steel with replaceable bearings. The camshaft is
gear-driven for excellent long-term timing stability.
The cylinder block is cast iron with
removable wet cylinder liners. Features include:
— High-strength casting for severe-duty operation
— Wet-sleeve design enabling full overhauls
— Deep reinforcing ribs to control vibration
— Full coolant circulation around liners for stable thermal
characteristics
The cast-iron cylinder head incorporates direct-injection combustion
chambers. There are two valves per cylinder—one intake and one
exhaust—actuated by rocker arms and pushrods.
Cold valve-lash clearances:
— Intake: 0.38–0.43 mm (0.015–0.017 in)
— Exhaust: 0.64–0.69 mm (0.025–0.027 in)
The head gasket uses fire rings for high-compression sealing. The head
is designed for long-term reliability under heavy loads.
The 3304 uses a mechanical direct-injection fuel system.
Major components include:
— Mechanical lift pump
— Primary water separator
— Secondary fine fuel filter
— Inline or rotary mechanical injection pump
— Mechanical multi-hole injectors
Injection pressures: 250–350 bar depending on pump type.
Fuel maintenance requirements:
— Fuel filters every 250–300 hr
— Drain water separator daily
— Injector inspection every 1,000–1,500 hr
— Injection-pump timing check during overhaul.
A full-pressure wet-sump lubrication system is used.
Oil capacity: 12–16 liters (12.7–17 qt).
Oil pressure:
— 300–450 kPa (44–65 psi) operating
— 100–150 kPa (15–22 psi) idle
Recommended oil: SAE 15W-40 (API CI-4 or higher)
Oil change interval: 250 hr.
Cooling is provided by a belt-driven centrifugal water pump.
Thermostat:
— Opening temperature: 82°C (180°F)
— Fully open: 95°C (203°F)
Cooling capacity: 14–20 liters (15–21 qt)
Cooling system pressure: 70–100 kPa (10–15 psi).
| Intake and Exhaust Systems |
Available configurations:
— Naturally aspirated
— Turbocharged (3304T)
— Turbo-aftercooled (3304TA, limited OEM applications)
Air filtration options:
— Single-stage dry-type filters
— Dual-stage heavy-duty filters
— Cyclone pre-cleaners for dusty environments
Turbocharged versions use wastegate-type turbochargers. Exhaust
manifolds are cast iron with high thermal durability.
| Electrical and Starting Systems |
Standard electrical configurations:
— 12-volt or 24-volt
— Alternators: 35–70 amps
— Starter motors: 2–4 kW
Basic sensor suite includes:
— Oil pressure switch
— Coolant temperature switch
— Speed/tachometer pickup
Electronic controls are typically not used on 3304 engines.
Depending on configuration, the engine may
support:
— Hydraulic pump drives
— PTO systems
— Compressor drives
— Generator heads
— Remote cooling packages.
Approximate dimensions:
— Length: 950–1,100 mm (37–43 in)
— Width: 750–850 mm (29–33 in)
— Height: 950–1,150 mm (37–45 in)
Dry weight: 820–900 kg (1,808–1,984 lb).
— Oil and filter: 250 hr
— Fuel filters: 250–300 hr
— Air filter: inspect every 50 hr
— Coolant: replace every 2 years
— Valve lash: every 1,000 hr
— Injector service: 1,000–1,500 hr
— Compression test: every 2,000 hr
— Belt inspection: every service interval.
— 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).
The Caterpillar 3304 engine is used in:
— CAT wheel loaders (936, 930 series)
— CAT excavators
— CAT graders (120 series)
— CAT industrial forklifts
— Agricultural tractors
— Compressors
— Generator sets (40–120 kW)
— Marine auxiliary power
— Pumps and hydraulic systems.
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