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Caterpillar 3056 Engine

The Caterpillar 3056 is a heavy-duty, 6.0-liter, inline 6-cylinder, four-stroke diesel engine designed for industrial applications, agricultural machinery, generator sets, and marine vessels. Built as a robust and highly serviceable platform, it utilizes either natural aspiration or turbocharging depending on the specific arrangement. The engine block features a conventional pushrod and rocker arm mechanism driven by a gear-train camshaft to control a two-valve-per-cylinder cylinder head arrangement.

The 3056 platform incorporates a direct-injection (DI) system delivering finely atomized fuel straight into the combustion chamber dome. Low-pressure fuel is pulled from the tank by a mechanical lift/transfer pump and routed through a heavy-duty twin spin-on secondary fuel filter array equipped with a manual fuel priming pump. Use a timing-gear-driven mechanical rotary distributor pump that schedules injection quantity and timing strictly via internal mechanical and hydraulic governors.

The lubrication circuit utilizes a pressure-regulated, closed-crankcase configuration. A low-mounted gear-driven oil pump (driven directly via the lower idler gear of the timing train) draws oil from the engine sump pan. Pressurized oil flows through an engine-mounted, integral plate-type oil cooler and passes into a twin spin-on oil filter assembly prior to feeding the main oil gallery. The system features a closed-loop crankcase breather and an electrical low-oil-pressure alarm sensor for safety shutdown. Standard oil system refill capacity averages 15 liters (3.9 gallons).

The engine relies on a liquid-jacket cooling circuit utilizing a gear-driven centrifugal water pump. Depending on the application, temperature regulation is managed either via a conventional radiator fan, a cupro-nickel tube heat exchanger, or keel cooling lines. Flow control is maintained by a mechanical thermostat assembly housed at the upper water jacket outlet. A dedicated de-aeration expansion tank prevents air pocket formation in the cylinder head jackets, and an electrical high-coolant-temperature switch monitors thermal thresholds.

General Technical Data

Engine Specifications

Engine Model ............... Caterpillar 3056
Engine Type ............... 4-cycle inline 6-cylinder direct injection liquid-cooled diesel
Number of Cylinders ............... 6
Cylinder Arrangement ............... In-line
Engine Bore, in (mm) ............... 3.94 (100.0)
Engine Stroke, in (mm) ............... 5.00 (127.0)
Displacement, cu.in (L) ............... 365 (6.0)
Rated Engine Power (Industrial), hp (kW) ............... 90-115 (67-87)
Rated Engine Power (Agricultural), hp (kW) ............... 90-115 (67-87)
Rated Engine Power (Marine), hp (kW) ............... 125 (93)
Rated Engine Speed (Industrial), rpm ............... 2200-2400
Rated Engine Speed (Agricultural), rpm ............... 2200-2400
Rated Engine Speed (Marine), rpm ............... 2600
Peak Torque ............... 475-515 Nm (350-380 lb-ft) at 1400-1600 rpm
Idle speed ............... 700-800 rpm
Aspiration Type ............... Naturally aspirated
Compression Ratio ............... 15.5:1-17.0:1
Firing Order ............... 1-5-3-6-2-4
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 wet-sump
Oil Pump Type ............... Gear-driven
Cooling System ............... Liquid-cooled
Water Pump Type ............... Gear-driven, centrifugal
Air Cleaner Type ............... Dry element
Starting System ............... Electric Starter
Electrical System ............... 12V or 24V
Alternator Rating, Amps ............... 65-85

Fuel System

Fuel System ............... Direct injection
Injection Pump Type ............... Mechanical
Fuel Injector Type ............... Multi-hole pencil-type
Governor Type ............... Mechanical
Fuel Type ............... Diesel Fuel

Dimensions and Weight

Overall Length, in (mm) ............... 41.3 (1050)
Overall Width, in (mm) ............... 25.2 (640)
Overall Height, in (mm) ............... 33.5 (850)
Dry Weight (Industrial), lbs (kg) ............... 1115 (505)
Dry Weight (Marine), lbs (kg) ............... 1345 (610)

Maintenance Data

Service Information

Thermostat begins opening ............... 82C (180F)
Thermostat fully open ............... 95C (203F)
Cooling system pressure ............... 70-90 kPa (10-13 psi)
Operating oil pressure ............... 300-420 kPa (44-61 psi)
Intake Valve Clearance, in (mm) ............... 0.008 (0.20)
Exhaust Valve Clearance, in (mm) ............... 0.018 (0.45)

Engine Oil and Coolant

Engine Oil Type .................. SAE 10W-30, 15W-40
API Service Classifications ......................... CH-4/SJ or higher
Engine Oil Capacity, qts (L) .................. 15.7 (15.0)
Coolant Capacity, qts (L) ............... 20.0 (19.0)

Service Intervals

Change oil and filter ............... Every 250 hours
Replace fuel filters ............... Every 500 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 ............... Every service cycle

Service Specifications

Cylinder Bore Inside Diameter, in (mm) ................ 3.9370-3.9382 (100.000-100.030)
Crankshaft Journal Outside Diameter, in (mm) ................ 2.9984-2.9992 (76.159-76.180)
Crank Pin Outside Diameter, in (mm) ................ 2.4992-2.5000 (63.479-63.500)
Crankshaft End Play, in (mm) ................ 0.0020-0.0150 (0.050-0.380)
Intake Valve Stem Outside Diameter, in (mm) ................ 0.3528-0.3537 (8.961-8.984)
Exhaust Valve Stem Outside Diameter, in (mm) ................ 0.3516-0.3525 (8.931-8.954)
Intake Valve Guide Inside Diameter (Installed), in (mm) ................ 0.3543-0.3553 (9.000-9.025)
Exhaust Valve Guide Inside Diameter (Installed), in (mm) ................ 0.3543-0.3553 (9.000-9.025)
Intake Valve Stem to Guide Clearance, in (mm) ................ 0.0006-0.0025 (0.016-0.064)
Exhaust Valve Stem to Guide Clearance, in (mm) ................ 0.0018-0.0037 (0.046-0.094)
Intake Valve Spring Free Length, in (mm) ................ 1.9189 (48.740)
Exhaust Valve Spring Free Length, in (mm) ................ 1.9189 (48.740)
Intake Cam Height, in (mm) ................ 1.1850-1.1913 (30.100-30.260)
Exhaust Cam Height, in (mm) ................ 1.1823-1.1886 (30.030-30.190)
Piston Pin Outside Diameter, in (mm) ................ 1.3748-1.3750 (34.920-34.925)
Piston Pin to Piston Bore Clearance, in (mm) ................ 0.0004-0.0012 (0.010-0.030)
Second Ring Side Clearance, in (mm) ................ 0.0028-0.0043 (0.070-0.110)
Oil Ring Side Clearance, in (mm) ................ 0.0020-0.0035 (0.050-0.090)
Top Ring End Gap, in (mm) ................ 0.0110-0.0220 (0.280-0.560)
Second Ring End Gap, in (mm) ................ 0.0110-0.0220 (0.280-0.560)
Oil Ring End Gap, in (mm) ................ 0.0110-0.0220 (0.280-0.560)

Tightening Torque Specs

Cylinder Head Bolts (Stage 1) ............... 90 Nm (66 lb-ft)
Cylinder Head Bolts (Stage 2) ............... 130 Nm (96 lb-ft)
Main Bearing Cap Bolts ............... 140 Nm (103 lb-ft)
Connecting Rod Cap Bolts ............... 90 Nm (66 lb-ft)
Flywheel Housing-to-Block Bolts ............... 75 Nm (55 lb-ft)
Flywheel-to-Crankshaft Bolts ............... 115 Nm (85 lb-ft)
Injector Clamp Bolt ............... 35 Nm (26 lb-ft)
Oil Pan Bolts ............... 27 Nm (20 lb-ft)
Fuel Injection Pump Mounting Nuts ............... 24 Nm (18 lb-ft)

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• Caterpillar Engines Specs
  
• Cat C6.6 Specs
  
• Cat 3054T Specs
  
• Cat 3054 Specs
  
• Cat 3054C Specs
  
• Cat 3054E Specs
  
• Cat 3056T Specs
  
• Cat 3056E Specs
  

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