Cat 3406A Specifications
| Engine Model: Caterpillar 3406A |
| Engine Type: 4-cycle inline 6-cylinder direct injection liquid-cooled diesel |
| Total Displacement: 893 cu.in (14.6 L) |
| Rated Engine Power: 250-425 Hp (186-317 kW) at 2000 rpm |
| Aspiration Type: Naturally aspirated or turbocharged |
____________________________________________________________________________________
The Caterpillar 3406A is one of Caterpillar’s
most respected heavy-duty diesel engines, known for its rugged
construction, long overhaul life, and reliable performance in trucking,
industrial, marine, and construction applications. Introduced in the
late 1970s as the first generation of the 3406 engine series, the 3406A
quickly earned a reputation for durability and serviceability. It was
designed to replace earlier Caterpillar on-highway engines such as the
1693 and to provide operators with a more fuel-efficient,
easier-to-maintain, and highly rebuildable platform.
With its mechanical fuel-injection system, direct-injection combustion
chambers, heavy cast-iron structure, and gear-driven components, the
3406A became a favorite among fleet operators, mechanics, and long-haul
truckers. Its strong torque curve, dependable cold-start capability, and
ability to run efficiently for high mileage made it a leading choice in
North American heavy trucking for many years. Today, many 3406A engines
remain in service due to their rebuildable design and extensive parts
availability.
The Caterpillar 3406A is a four-stroke, water-cooled, inline
six-cylinder diesel engine. Total displacement is 14.6 liters (893 cubic
inches). Bore is 137 mm (5.40 in), and stroke is 165 mm (6.50 in). The
engine’s long-stroke configuration contributes to strong low-speed
torque and high pulling power. Compression ratio varies by rating but
generally ranges from 14.5:1 to 15.5:1.
Horsepower ratings vary widely depending on
application:
– On-highway truck engines: 285–425 hp (213–317 kW) at 1,800–2,100 rpm
– Industrial engines: 250–400 hp (186–298 kW) at 1,800–2,100 rpm
– Marine propulsion: 250–365 hp (186–272 kW) at 1,800–2,100 rpm
Peak torque typically falls between: 1,600 and 1,900 Nm (1,180–1,400
lb-ft) at 1,200–1,400 rpm. Idle speed is generally 600–650 rpm. Governed
speed varies from 1,900 to 2,100 rpm. Firing order is 1-5-3-6-2-4.
The crankshaft is a forged-steel, fully counterweighted unit supported
by seven large main bearings. Pistons are forged-aluminum alloy with
reinforced crowns, cooling galleries, and machined direct-injection
combustion bowls. Connecting rods are forged steel with replaceable
bearing inserts. The camshaft is gear-driven and mounted in the block
for long-term timing accuracy.
The 3406A cylinder block is a heavy, cast-iron structure with thick
cylinder walls, deep stiffening ribs, and large main bearing saddles.
The block is engineered for long service life and can be repeatedly
overbored during major rebuilds. Coolant passages are cast around each
cylinder for optimal heat transfer under heavy load conditions. The
crankcase design reduces torsional stress and vibration.
The cylinder head is cast iron and uses direct-injection combustion
chambers. Most 3406A versions use two valves per cylinder—one intake,
one exhaust—though later transitional units toward the B-series adopted
improved airflow characteristics. Valves are actuated by rocker arms and
pushrods from the camshaft.
Typical cold valve-lash settings:
– Intake: 0.38–0.43 mm (0.015–0.017 in)
– Exhaust: 0.64–0.69 mm (0.025–0.027 in)
Valve seats are hardened steel inserts. The head gasket includes fire
rings for high-pressure sealing.
The Caterpillar 3406A uses a fully mechanical fuel-injection system. A
mechanical lift pump draws diesel through primary and secondary filters,
delivering it to a mechanically governed inline high-pressure
fuel-injection pump. Fuel is distributed via high-pressure lines to
multi-hole injectors that deliver atomized fuel directly into the
combustion bowls. Injection pressures typically range from: 250–350 bar
depending on timing and application
The mechanical governor controls fuel rate and engine speed. Injection
timing can be adjusted mechanically and must be set accurately during
overhaul or pump replacement.
Fuel system maintenance:
– Replace fuel filters every 250–300 hours
– Drain water separator regularly
– Injectors serviced every 1,000–1,500 hours
– Injection pump calibration at major service intervals.
The 3406A uses a high-capacity, full-pressure wet-sump lubrication
system. A gear-driven oil pump circulates oil through full-flow and
bypass filters before distributing it to all major components. Oil
capacity: 36–42 liters (38–44 US quarts)
Typical oil pressure:
– 345–550 kPa (50–80 psi) at rated speed
– 140–275 kPa (20–40 psi) at idle
Recommended oil viscosities include SAE 15W-40 or straight-weight oils
such as SAE 30 or 40 for warm climates. Oil change intervals commonly
range 250–350 hours depending on duty cycle.
Cooling is handled by a belt- or gear-driven centrifugal water pump
circulating coolant through the block, head, and aftercooler (if
equipped). The thermostat begins opening at approximately 82°C (180°F)
and reaches full open at 95°C (203°F).
Cooling capacity varies with application but generally ranges: 30–45
liters (32–47 US quarts). Radiator cap pressure is typically 70–100 kPa
(10–15 psi). Aftercooled versions include air-to-air or jacket-water
aftercoolers.
| Intake and Exhaust Systems |
Air intake design depends on application:
– Truck engines: large dry-element filters
– Industrial engines: heavy-duty dual-stage systems
– Marine engines: water-separated intake systems
Turbocharged versions use a single turbocharger feeding an intake
manifold. Some versions include aftercoolers for improved thermal
efficiency.
Exhaust manifolds are heavy cast iron designed to withstand prolonged
thermal cycling. Marine engines often include water-jacketed exhaust
systems.
| Electrical and Starting Systems |
Electrical configurations differ by
application:
– 12-volt systems (common in trucks)
– 24-volt systems (industrial and marine)
Alternators typically output 35–100 amps. Starters are 4–7 kW depending
on climate. Electrical components include senders for oil pressure,
coolant temperature, and optional tachometer sensors.
Depending on configuration, the 3406A may
support:
– PTO drive systems
– Hydraulics
– Air compressors
– Marine gearboxes
– Generator heads
– Pumps and industrial drives.
Approximate dimensions:
– Length: 1,500–1,650 mm (59.1–65.0 in)
– Width: 900–1,050 mm (35.4–41.3 in)
– Height: 1,100–1,250 mm (43.3–49.2 in)
Dry weight varies by setup: 1,300–1,450 kg (2,866–3,196 lb).
– Oil and filter: every 250–350 hours
– Fuel filters: every 250–300 hours
– Air filters: inspect every 50 hours
– Coolant replacement: every 2 years
– Valve lash: every 1,000 hours
– Injector service: 1,000–1,500 hours
– Compression testing: every 2,000 hours
– Turbo inspection: every 2,000 hours.
– 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).
The Caterpillar 3406A was used in:
– Heavy-duty on-highway trucks (Freightliner, Peterbilt, Kenworth,
International)
– Construction equipment (loaders, graders, scrapers)
– Mining equipment
– Marine propulsion systems
– Industrial power units
– Generator sets
– Oilfield drilling and pumping equipment.
____________________________________________________________________________________
| Industrial Engines Technical Specifications |
| Small Engines Technical Specifications |
| Car Engines Technical Specifications |
| Outboard Engines Technical Specifications |
