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Cummins ISB 6.7 Engine

The Cummins ISB6.7 is an inline six-cylinder, four-stroke, medium-duty diesel engine widely utilized across commercial trucking, school buses, emergency vehicles, and heavy-duty pickup applications. Serving as the largest displacement evolution of the B-series engine family, this unit utilizes a high-strength cast-iron block with parent-metal cylinder bores and a single-piece cast-iron cylinder head. To mitigate cabin NVH (noise, vibration, and harshness), it features a rear-mounted gear train architecture.

The engine operates under full electronic management via an advanced Engine Control Module (ECM), which dynamically controls the variable geometry turbocharger (VGT) and exhaust aftertreatment subsystems to balance strict emissions compliance with high thermal efficiency. The valvetrain utilizes an Overhead Valve (OHV) configuration actuated by a single block-mounted camshaft. The cylinder head features a 4 valves per cylinder cross-flow design (12 intake valves, 12 exhaust valves) to optimize volumetric efficiency and gas exchange. Valves are operated via solid pushrods, overhead rocker arms, and dual-valve actuator bridges.

Fuel delivery is managed via a Bosch High-Pressure Common Rail (HPCR) injection system. A mechanical, gear-driven high-pressure pump (such as the Bosch CP4.2 or CP3, depending on the model year) pressurizes a shared fuel rail to operating pressures exceeding 1800 bar. Low-pressure delivery is handled by an electric lift pump through a multi-stage fuel filtration assembly incorporating a water-in-fuel (WIF) sensor. Centrally located, vertical electronic injectors utilize solenoid or piezoelectric actuators to deliver multi-injection events (pilot, main, and post-injection pulses) directly into the piston combustion bowls based on real-time commands from the ECM.

The lubrication circuit is pressurized by a high-capacity, crankshaft-driven gerotor oil pump located at the front of the engine block. Pressurized oil is routed directly through an integral liquid-to-liquid plate-type oil cooler before entering a combination full-flow/bypass spin-on oil filter assembly. The cylinder block features integrated piston cooling nozzles (cooling jets) that spray oil at the undersides of the pistons to manage crown temperatures.

Thermal regulation is achieved via a closed-loop, forced-circulation liquid cooling system. A high-flow centrifugal water pump is integrated into the front engine cover and driven by a serpentine accessory belt. Flow routing through the radiator circuit is modulated by a single front-mounted thermostat. The standard regulated operational temperature band is maintained between 82C and 95C (180F to 203F) to support proper regeneration temperatures within the downstream diesel particulate filter (DPF).

General Technical Data

Engine Specifications

Engine Model ............... Cummins ISB6.7
Engine Type ............... 4-cycle inline 6-cylinder common rail direct injection liquid-cooled diesel
Number of Cylinders ............... 6
Cylinder Arrangement ............... In-line
Engine Bore, in (mm) ............... 4.21 (107.0)
Engine Stroke, in (mm) ............... 4.88 (124.0)
Displacement, cu.in (L) ............... 409 (6.7)
Rated Engine Power, hp (kW) ............... 197-320 (147-240)
Rated Engine Speed, rpm ............... 2200-2800
Peak Torque ............... 700-1100 Nm (516-811 lb-ft) at 1300-1600 rpm
Idle Speed ............... 700-800 rpm
Aspiration Type ............... Turbocharged
Compression Ratio ............... 16.5:1-17.3:1
Firing Order ............... 1-5-3-6-2-4
Cylinder Block Type ............... Cast iron
Cylinder Head Type ............... Cast iron
Lubrication System ............... Full-pressure
Oil Pump Type ............... Gear-driven
Oil Filter Type ............... Full-flow, spin-on
Cooling System ............... Liquid-cooled
Water Pump Type ............... Belt-driven, centrifugal
Air Cleaner Type ............... Dry dual-stage
Starting System ............... Electric Starter
Electrical System ............... 12V or 24V
Alternator Rating, Amps ............... 70-120

Fuel System

Fuel System ............... Common rail direct injection (HPCR)
Fuel System Control ............... Electronic
Governor Type ............... Electronic
Injection Pressure ............... 1800 bar
Fuel Type ............... Diesel Fuel

Dimensions and Weight

Overall Length, in (mm) ............... 40.3-49.4 (1050-1250)
Overall Width, in (mm) ............... 29.6-35.5 (750-900)
Overall Height, in (mm) ............... 39.4-49.4 (1000-1250)
Dry Weight, lbs (kg) ............... 1055-1320 (480-600)

Maintenance Data

Service Information

Thermostat begins opening ............... 82C (180F)
Thermostat fully open ............... 95C (203F)
Cooling system pressure ............... 70-100 kPa (10-15 psi)
Operating oil pressure ............... 275-380 kPa (40-55 psi)
Idle oil pressure ............... 70-100 kPa (10-15 psi)
Intake Valve Clearance, in (mm) ............... 0.254 (0.010)
Exhaust Valve Clearance, in (mm) ............... 0.508 (0.020)

Engine Oil and Coolant

Engine Oil Type .................. SAE 10W-30, 15W-40
API Service Classifications ......................... CI-4, CJ-4, CK-4
Engine Oil Capacity, qts (L) .................. 13.7-18.9 (13.0-18.0)
Coolant Capacity, qts (L) ............... 18.9-26.3 (18.0-25.0)

Service Intervals

Change oil and filter ............... Every 250 hours
Replace fuel filters ............... Every 300 hours
Inspect air filter ............... Every 100 hours
Replace air filter ............... Every 300 hours
Change coolant ............... Every 2000 hours
Valve-lash adjustment ............... Every 1000 hours
Injector inspection ............... Every 1500-2000 hours
Compression test ............... Every 2500 hours
Drain water separator ............... As required
Belt inspection ............... As required

Service Specifications

Cylinder Bore Inside Diameter, in (mm) ............... 4.2126-4.2146 (107.000-107.050)
Crankshaft Journal Outside Diameter, in (mm) ............... 3.2669-3.2689 (82.980-83.030)
Crank Pin Outside Diameter, in (mm) ............... 2.7155-2.7175 (68.975-69.025)
Crankshaft End Play, in (mm) ............... 0.0047-0.0169 (0.119-0.429)
Intake Valve Stem Outside Diameter, in (mm) ............... 0.2740-0.2752 (6.960-7.040)
Exhaust Valve Stem Outside Diameter, in (mm) ............... 0.2736-0.2748 (6.950-7.030)
Intake Valve Guide Inside Diameter, in (mm) ............... 0.2756-0.2772 (7.000-7.040)
Exhaust Valve Guide Inside Diameter, in (mm) ............... 0.2756-0.2772 (7.000-7.040)
Intake Valve Stem to Guide Clearance, in (mm) ............... 0.0010-0.0030 (0.025-0.076)
Exhaust Valve Stem to Guide Clearance, in (mm) ............... 0.0015-0.0035 (0.038-0.089)
Intake Valve Spring Free Length, in (mm) ............... 1.960-1.990 (49.78-50.54)
Exhaust Valve Spring Free Length, in (mm) ............... 1.960-1.990 (49.78-50.54)
Intake Cam Height, in (mm) ............... 2.115-2.135 (53.72-54.23)
Exhaust Cam Height, in (mm) ............... 2.095-2.115 (53.21-53.72)
Piston Pin Outside Diameter, in (mm) ............... 1.5746-1.5748 (39.995-40.000)
Piston Pin to Piston Bore Clearance, in (mm) ............... 0.0002-0.0007 (0.005-0.018)
Second Ring Side Clearance, in (mm) ............... 0.0020-0.0045 (0.050-0.114)
Oil Ring Side Clearance, in (mm) ............... 0.0010-0.0030 (0.025-0.076)
Top Ring End Gap, in (mm) ............... 0.0100-0.0170 (0.254-0.432)
Second Ring End Gap, in (mm) ............... 0.0160-0.0260 (0.406-0.660)
Oil Ring End Gap, in (mm) ............... 0.0100-0.0220 (0.254-0.559)

Tightening Torque Specs

Cylinder head bolts ............... 180-210 Nm (133-155 lb-ft)
Main bearing caps ............... 150-180 Nm (111-133 lb-ft)
Connecting rod bolts ............... 70-90 Nm (52-66 lb-ft)
Flywheel bolts ............... 220-260 Nm (162-192 lb-ft)
Crankshaft pulley bolt ............... 270-300 Nm (199-221 lb-ft)
Oil drain plug ............... 40-50 Nm (30-37 lb-ft)
Injector hold-down bolts ............... 25-30 Nm (18-22 lb-ft)

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• Cummins Engines Specs
  
• Cummins ISB 3.9 Specs
  
• Cummins ISB 4.5 Specs
  
• Cummins ISB 5.9 Specs
  

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