Cat 3408 Specifications
| Engine Model: Caterpillar 3408 |
| Engine Type: 4-cycle 8-cylinder turbocharged and aftercooled diesel |
| Total Displacement: 1099 cu.in (18.0 L) |
| Rated Engine Power: 300-600 Hp (220-450 kW) at 2000 rpm |
| Fuel System Type: Mechanical unit injector (MUI) |
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The Caterpillar 3408 is a V-8 configuration,
18.0-liter heavy-duty diesel engine engineered for maximum power and
torque in the most severe off-highway and industrial applications. This
engine represents a significant step up in displacement and capability
from the 3306 and 3406 inline-six platforms, providing a compact yet
immensely powerful solution for large machinery.
Characterized by its 65-degree V-block, replaceable wet cylinder liners,
and mechanically controlled unit injection fuel system, the 3408 is
built for durability under continuous high load. Available in
turbocharged and turbocharged-aftercooled configurations, it delivers
substantial horsepower and exceptional lugging ability. Its design
prioritizes serviceability within a relatively compact package, making
it a favored powerplant for large track-type tractors, mining trucks,
marine vessels, and stationary industrial equipment where absolute
reliability and prodigious torque are fundamental requirements.
Engine Type: 65-Degree V-8, Four-Stroke Cycle Diesel.
Aspiration: Turbocharged (T) or Turbocharged and Aftercooled (TA).
Displacement: 18.0 Liters (1099 cubic inches).
Bore: 137 mm (5.4 inches).
Stroke: 165 mm (6.5 inches).
Engine Power (Industrial/GenSet): 300-600 hp (220-450 kW).
Engine Power (Trucking): 425-550 hp (317-410 kW).
Engine Power (Marine): 440-520 hp (328-388 kW).
Compression Ratio: 14.5:1.
Firing Order: 1-8-7-5-4-3-6-2.
Rotation (Viewed from Flywheel End): Counterclockwise.
Governor Type: Mechanical, all-speed or variable speed.
Emission Certification: Pre-Tier and early Tier 1 compliant mechanical
engine.
The cylinder block is a heavy-duty, 65-degree V-style cast iron
structure. The 65-degree angle provides an optimal balance between
engine width, crankshaft balance, and firing interval smoothness. It
incorporates replaceable wet-type cylinder liners for all eight
cylinders. The liners are pressed into the block and sealed at the top
with a copper composition gasket under a precision-machined flange.
The block features a deep skirt design and employs cross-bolted main
bearing caps for maximum crankshaft support. The camshaft is located in
the center of the "V" and is gear-driven from the crankshaft. The
block's construction is designed to manage extreme torsional and bending
loads.
Two separate cast iron cylinder heads are used, one for each cylinder
bank. Each head employs a four-valve-per-cylinder design - two intake
and two exhaust - to manage the high airflow requirements of the large
displacement. Valve seat inserts are hardened for durability under high
thermal stress.
Valve guides are pressed into the head and are replaceable. Valve
actuation is via pushrods and rocker arms; the rocker arms are
shaft-mounted on each cylinder head. Valve lash requires manual
adjustment using a screw and locknut on each rocker arm. The cylinder
head gaskets are solid copper or heavy-duty composite designs.
The engine utilizes a direct injection, mechanically controlled fuel
system. It employs Caterpillar's Mechanical Unit Injector (MUI) system,
where each cylinder has a unit injector actuated by the engine's
camshaft via pushrods and rockers. The injector combines the pumping
element and nozzle, generating high injection pressure mechanically.
Fuel rack setting and timing are mechanical adjustments performed on the
unit injectors. A gear-type transfer pump supplies fuel from the tank.
The fuel circuit includes a primary filter/water separator and a
secondary spin-on fuel filter. This system is mechanically robust and
field-serviceable.
Lubrication is provided by a high-volume gear-type oil pump driven from
the front gear train. Oil is drawn from a deep, cast aluminum sump
through a pickup tube and screen. It is then forced through dual
full-flow, spin-on oil filters operating in parallel. A bypass valve
protects the system.
Filtered oil is routed through a large, integral plate-type oil cooler
before entering the main oil gallery. From the gallery, oil is
distributed to the crankshaft main and connecting rod bearings, camshaft
bearings, turbocharger(s), and valve train. Piston cooling jets spray a
directed stream of oil onto the underside of each piston.
Coolant circulation is managed by a single, gear-driven centrifugal
water pump mounted at the front of the engine in the "V". The pump feeds
coolant into two separate passages, one for each cylinder bank. Coolant
flows through block and head passages. A wax-pellet thermostat regulates
engine operating temperature.
On Turbocharged Aftercooled (TA) models, a jacket water aftercooler
(JWAC) uses engine coolant to lower the temperature of the turbocharged
intake air. The engine cooling system requires a radiator or heat
exchanger of very large capacity. A coolant conditioner filter is
standard.
Starting System: 24-volt or 32-volt electric starting motor. Air
starting systems are standard equipment on most industrial and mining
applications. Charging System: Dual heavy-duty brushless alternators are
common, with combined outputs exceeding 200 amperes to support large
electrical loads.
Air Intake System: Dual dry-type air cleaners, one for each bank, are
standard, each with a restriction indicator. On turbocharged models, air
is routed through the turbocharger(s) and, if equipped, the aftercooler
before entering the intake manifold located in the valley. Exhaust
System: Separate cast iron exhaust manifolds for each bank route gases
to the turbocharger(s). A wastegate regulates boost pressure.
Dimensions are substantial due to the engine's large displacement and
V-8 configuration. For a standard industrial configuration, approximate
length is 2032 mm (80.0 inches), width is 1549 mm (61.0 inches), and
height is 1651 mm (65.0 inches). The net dry engine weight, excluding
fluids but including standard accessories like dual alternators and an
air compressor, is approximately 1678 kg (3700 pounds). This significant
weight is a direct result of the massive block, crankshaft, and heavy
internal components.
Engine Oil Grade: Use Caterpillar Diesel Engine Oil (DEO) or an
equivalent oil meeting API CD, CE, or CF-4 specifications. SAE 15W-40 is
standard for general operation. Oil Change Interval: Dictated by severe
service conditions. In mining or heavy construction, intervals of 250
hours are standard. Oil analysis is essential for monitoring condition.
Oil System Capacity: Total refill capacity, including dual filter
changes, is approximately 75.7 Liters (20.0 US gallons).
Fuel Filter: Replace primary and secondary fuel filter elements every
500 hours. Air Filter: Service or replace based on restriction gauge
indication. Dual filters require individual service. Valve Lash
Adjustment (Cold): Intake: 0.38 mm (0.015 in). Exhaust: 0.76 mm (0.030
in). Adjust at initial break-in and every subsequent 1000 hours of
operation.
Cooling System Capacity: Total cooling system capacity, including
radiator, is approximately 113.6 Liters (30.0 US gallons). Engine
Coolant: Use a 50/50 mixture of ethylene glycol antifreeze and
demineralized water. Maintain proper concentration of supplemental
coolant additive (SCA) via a coolant filter. Preventing liner cavitation
is critical.
Cylinder Head Bolts: Tighten in a specific sequence. Final torque: 300
Nm (221 lb-ft).
Main Bearing Cap Bolts (Vertical): 340 Nm (250 lb-ft).
Main Bearing Cap Cross Bolts: 160 Nm (118 lb-ft).
Connecting Rod Cap Bolts: 230 Nm (170 lb-ft) plus an additional
60-degree turn.
Flywheel Housing-to-Block Bolts: 190 Nm (140 lb-ft).
Flywheel-to-Crankshaft Bolts: 340 Nm (250 lb-ft).
Unit Injector Clamp Bolt: 50 Nm (37 lb-ft).
Oil Pan Bolts: 55 Nm (41 lb-ft).
Oil Filter Cartridge: Hand-tighten until gasket contacts base, then
tighten an additional three-quarters turn.
The Caterpillar 3408 engine powered the
largest mobile equipment:
Track-Type Tractors: Caterpillar D8H, D8K, D8L, D9H, D9L, and D10. Wheel
Loaders: Caterpillar 988B, 992C, 992D. Off-Highway Trucks: Caterpillar
769C, 773B, 777B. Mining Equipment: Primary power for large front-end
loaders, blast hole drills, and bulldozers. Marine Propulsion: Used in
larger commercial fishing vessels, tugboats, crew boats, and yachts
(70-120 feet), commonly rated at 443 hp at 1800 rpm for continuous duty.
Industrial: Powered the largest generator sets (500-1000 kW), large
hydraulic pumps, and oilfield drilling rig drawworks. Locomotives:
Served as prime power in heavy-duty industrial and switching
locomotives. Specialty: Powered large rock crushers, slurry pumps, and
airport snow blowers.
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