Cat 3406 Specifications
| Engine Model: Caterpillar 3406 |
| Engine Type: 4-cycle inline 6-cylinder turbocharged and aftercooled diesel |
| Total Displacement: 893 cu.in (14.6 L) |
| Rated Engine Power: 255-482 Hp (190-359 kW) at 2000 rpm |
| Fuel System Type: Mechanical unit injector |
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The Caterpillar 3406 is an inline six-cylinder,
14.6-liter heavy-duty diesel engine that stands as an icon of durability
and performance in the on-highway trucking and industrial sectors. As
the successor to the 3306, it represents a significant increase in
displacement and power, engineered for long-haul transportation,
severe-service vocational trucks, and demanding stationary applications.
This engine is characterized by its massive deep-skirt block,
cross-bolted main bearings, and wet cylinder liner design, all hallmarks
of Caterpillar's heavy-duty philosophy.
Throughout its long production run, the 3406 evolved from a mechanically
governed engine to an electronically controlled powerhouse, with the
later 3406E model setting industry standards. Its reputation for
million-mile longevity, exceptional torque rise, and overall reliability
made it one of the most sought-after and respected diesel engines in
North American trucking history.
Engine Type: Inline 6-Cylinder, Four-Stroke Cycle Diesel.
Aspiration: Turbocharged and Aftercooled (Air-to-Air or Jacket Water).
Displacement: 14.6 Liters (893 cubic inches).
Bore: 137 mm (5.4 inches).
Stroke: 165 mm (6.5 inches).
Engine Power (Industrial): 465 hp (347 kW) at 1800-2100 rpm.
Engine Power (Pump): 292-482 hp (218-359 kW) at 1750-2300 rpm.
Engine Power (Truck): 255-400 hp (190-298 kW).
Compression Ratio: 14.5:1.
Firing Order: 1-5-3-6-2-4.
Rotation (Viewed from Flywheel End): Counterclockwise.
Governor Type: Mechanical (early models)
Emission Certification: Ranged from pre-Tier through EPA 1998.
The cylinder block is an immense, deep-skirt cast iron structure
providing unparalleled rigidity. It incorporates replaceable wet-type
cylinder liners. The liners are pressed into the block and sealed at the
top with a copper gasket under a precision-machined flange. The lower
end features a cross-bolted main bearing design of exceptional strength.
Each of the seven nodular iron main bearing caps is secured by two
vertical bolts and two horizontal cross bolts that thread deep into the
block's lower skirt. This design creates an immensely stable crankshaft
environment capable of withstanding extreme cylinder pressures. The
camshaft is gear-driven and rotates within bearings machined directly
into the block.
A single cast iron cylinder head is used, secured by four bolts per
cylinder. The head employs a four-valve-per-cylinder design - two intake
and two exhaust - on most turbocharged-aftercooled models to optimize
airflow for high power output. Valve seat inserts are hardened for
maximum durability.
Valve guides are replaceable. Early mechanical engines used adjustable
rocker arms, while later electronic engines incorporated hydraulic lash
adjusters. Rocker arms are shaft-mounted. The cylinder head gasket is a
multi-layer steel (MLS) or solid copper design.
The fuel system evolved significantly. Early 3406 and 3406B engines used
a mechanically governed, camshaft-driven unit injector system (Pencil
Injectors). The 3406B with PEEC (Programmable Electronic Engine Control)
and the 3406E introduced the Electronically Controlled Unit Injector
(EUI).
In the EUI system, the camshaft provides actuation force, while an
electronic control module (ECM) precisely governs injection timing and
duration via a solenoid on each injector. A gear-type transfer pump
supplies fuel. This system enabled injection pressures exceeding 25,000
psi (1725 bar) for improved efficiency and power.
Lubrication is provided by a high-volume gear-type oil pump. Oil is
drawn from a deep, cast aluminum or fabricated steel sump through a
pickup tube and screen. It is forced through a full-flow, spin-on or
canister-type oil filter. A bypass valve protects the system. Filtered
oil is routed through a large oil cooler before entering the main
gallery.
From there, oil is distributed to all main, rod, and camshaft bearings,
the turbocharger, and the valve train. Piston cooling jets spray a
dedicated stream of oil onto the underside of each piston. The system is
designed to maintain stable pressure and provide ample cooling under
maximum load.
Coolant circulation is managed by a gear-driven centrifugal water pump.
Coolant flows through block and head passages designed for optimal heat
transfer. A wax-pellet thermostat regulates operating temperature.
The system employs an air-to-air aftercooler (ATAAC) on highway engines
to cool turbocharged intake air, with jacket water aftercooling (JWAC)
common on industrial models. The cooling system has substantial capacity
and requires a large radiator or heat exchanger. A coolant conditioner
filter is standard to maintain additive levels and prevent liner
cavitation.
Starting System: 12-volt, 24-volt, or 32-volt electric starting; air
starting was a common option for vocational and industrial applications.
Charging System: A heavy-duty brushless alternator, with outputs from
105 to 160 amperes.
Air Intake System: A dry-type, two-stage air cleaner system with a
primary safety element and a main filter, equipped with a restriction
indicator. Exhaust System: A divided-entry cast iron exhaust manifold
optimizes turbocharger response. A wastegate regulates boost pressure.
The engine's dimensions reflect its large displacement. For a standard
on-highway truck configuration, approximate length is 1829 mm (72.0
inches), width is 1118 mm (44.0 inches), and height is 1397 mm (55.0
inches). The net dry engine weight, including standard accessories like
alternator and air compressor, is 1487 kg (3278 pounds). Its substantial
weight is a direct consequence of its heavy-duty construction and large
internal components.
Engine Oil Grade: Use oil meeting Caterpillar's specifications. For
mechanical engines, API CG-4/CH-4. For EUI engines (3406E), Cat ECF-1-a
or API CH-4/CI-4 is mandatory. SAE 15W-40 is standard.
Oil Change Interval: Extended intervals were possible with electronic
engines and oil analysis. Common intervals ranged from 25,000 to 50,000
miles (40,000-80,000 km) for on-highway use. Severe service followed
250-500 hour guidelines. Oil System Capacity: Total refill capacity,
including filter change, is 41.6 Liters (11.0 US gallons).
Cooling System Capacity: Total cooling system capacity is approximately
68.1 Liters (18.0 US gallons). Fuel Filter: Replace primary and
secondary fuel filter elements at scheduled intervals, often every
30,000 miles (48,000 km) or 500 hours. Air Filter: Service based on
restriction gauge indication. The primary safety element is serviceable.
Valve Lash Adjustment: Mechanical engines: Intake 0.38 mm (0.015 in),
Exhaust 0.76 mm (0.030 in) cold. Adjust every 1000 hours. Engine
Coolant: Use Caterpillar Extended Life Coolant (ELC) or a conventional
50/50 ethylene glycol mix with properly maintained Supplemental Coolant
Additive (SCA) levels.
Cylinder Head Bolts: Tighten in a specific sequence. Final torque: 300
Nm (221 lb-ft) plus a 90-degree turn.
Main Bearing Cap Bolts (Vertical): 340 Nm (250 lb-ft) plus a 90-degree
turn.
Main Bearing Cap Cross Bolts: 190 Nm (140 lb-ft).
Connecting Rod Cap Bolts: 190 Nm (140 lb-ft) plus a 90-degree turn.
Flywheel Housing-to-Block Bolts: 190 Nm (140 lb-ft).
Flywheel-to-Crankshaft Bolts: 285 Nm (210 lb-ft).
Unit Injector Clamp Bolt (EUI): 35 Nm (26 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 3406 engine dominated heavy-duty applications:
On-Highway Trucks: The engine of choice for premium long-haul tractors
from Peterbilt (379, 387), Kenworth (W900, T600, T2000), Freightliner
(FLD120, Classic), and Navistar (9300, 9400). Construction/Mining:
Powered Caterpillar 769, 773 Rock Trucks; 988, 992 Wheel Loaders; D8, D9
Track-Type Tractors; and large excavators. Marine Propulsion: Used in
larger commercial vessels, tugboats, and fishing boats as a
high-horsepower propulsion engine.
Power Generation: A prime mover for large generator sets in the 300-750
kW range. Oil and Gas: Powered the largest frac pumps, cement pumps, and
drilling rig components. Locomotives: Served as the prime power in many
industrial and regional locomotives. Specialty: The standard power for
heavy-duty fire apparatus, snow blowers, and airport crash trucks.
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