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Detroit Diesel 671 Non-Turbo 2-Valve Engine Specifications & Applications

Introduction to the Detroit Diesel 671 Non-Turbo 2-Valve Engine

The Detroit Diesel 671 non-turbo 2-valve engine is part of the iconic Series 71 two-stroke diesel engine family and is widely considered one of the most dependable powerplants in marine, industrial, and standby generator applications. Known for its mechanical simplicity, long lifespan, and rugged performance, the naturally aspirated 671 with 2 valves per cylinder remains a favorite among fleet operators, boat owners, and diesel mechanics alike.

Unlike newer, electronically controlled engines, the 671 non-turbo 2-valve variant is fully mechanical and easy to service. It features six inline cylinders, a two-stroke cycle, and a proven mechanical injector system. The engine's simple 2-valve-per-cylinder head design ensures straightforward maintenance, while its naturally aspirated configuration provides dependable operation without relying on turbo components that may fail under harsh conditions.

At Diesel Pro Power, we support this legendary engine with a complete line of aftermarket parts designed to fit perfectly, perform flawlessly, and ship quickly—backed by expert technical support and a solid warranty.

Technical Specifications of the Detroit Diesel 671 Non-Turbo 2-Valve Engine

Core Engine Specs

  • Engine Series: Detroit Diesel 71 Series

  • Model: 671 (6 cylinders in inline configuration)

  • Displacement: 426 cubic inches (6.99 liters)

  • Cycle: 2-Stroke Diesel

  • Valvetrain: 2 valves per cylinder (1 intake, 1 exhaust)

  • Aspiration: Naturally Aspirated (no turbo)

  • Firing Order: 1-5-3-6-2-4

  • Compression Ratio: ~17:1

  • Injection System: Mechanical unit injector system (pressure-timed)

  • Governor Types: Limiting and variable-speed mechanical governors

Bore and Stroke

  • Bore: 4.25 inches (108 mm)

  • Stroke: 5.00 inches (127 mm)

Performance and Power

  • Horsepower Output: 190–230 HP depending on injectors and RPM setting

  • Rated Speed Range: 1,800 to 2,100 RPM (variable by application)

  • Torque Output: Approx. 500–600 lb-ft

Oil & Cooling System Capacities

  • Oil Capacity with Filter: Approx. 10 gallons (37.9 liters)

  • Coolant Capacity: Approx. 7.5 gallons (28.4 liters)

  • Oil Pressure (Operating): 40 – 60 PSI at full load

  • Operating Temperature Range: 170°F – 195°F

  • Max Coolant Temperature: 200°F

Engine Dimensions and Weight

  • Dry Weight (Base Engine): ~2,185 lbs (991 kg)

  • Length: ~67 inches (170 cm)

  • Width: ~30 inches (76 cm)

  • Height: ~40 inches (102 cm)

Key Features of the 671 Non-Turbo 2-Valve Engine

Simple and Reliable

With no turbo and a 2-valve head, the 671 is a straightforward engine built for reliability and ease of service. The mechanical unit injectors eliminate the need for high-pressure fuel rails or ECU calibration.

Modular Cylinder Heads

Each cylinder features its own replaceable cylinder head. This modularity allows for isolated repairs—meaning a single head can be swapped out without removing the entire top end.

High Low-End Torque

While not built for high speeds, the 671 delivers excellent torque at low RPMs—perfect for boats and equipment that prioritize pulling power and steady operation.

Cold Weather Performance

The naturally aspirated version starts well in cold climates, especially when paired with block heaters or ether injection systems. It performs consistently across a wide temperature range.

Marine Applications of the Detroit Diesel 671 Non-Turbo 2-Valve

This engine was designed with marine use in mind and has seen decades of service across commercial and recreational fleets.

Recreational Marine Use

  • Classic Yachts and Trawlers: Used in Grand Banks, Hatteras, and similar long-range cruisers from the 1950s through the 1980s.

  • Sailboat Auxiliary Engines: Ideal for larger displacement sailboats needing reliable diesel propulsion.

  • Liveaboard Vessels: Valued for low-RPM cruising and exceptional fuel economy.

Commercial Marine Use

  • Tugboats: Ideal for harbor pushing, barge transport, and towboat configurations.

  • Fishing Boats: Used in shrimpers, crabbers, and gillnetters throughout North and Central America.

  • Landing Craft: Popular in shallow-draft military landing craft.

  • Workboats and Barges: Found in dredging equipment and port utility vessels.

Industrial Applications of the Detroit 671 2-Valve Engine

The engine's robust mechanical design makes it a top choice for high-load, continuous-duty applications.

  • Power Generation: Found in 60–100 kW generator sets across mining, emergency, and industrial facilities.

  • Water Pumping Systems: Used in irrigation and municipal water supply.

  • Compressors and Blowers: Drives large industrial air compressors and pneumatic equipment.

  • Construction Machinery: Formerly used in cranes, rock crushers, and earthmovers.

  • Oilfield Service Units: Used in pipe handling machines and rig equipment.

  • Military Equipment: Installed in vehicles and stationary power units worldwide.

Why Mechanics and Fleet Operators Still Choose the 671 Non-Turbo 2-Valve

  • Mechanical Dependability: No electronic control modules, sensors, or turbo components to fail.

  • Parts Availability: Diesel Pro Power offers all major components with same-day shipping.

  • Easy Field Service: The engine can be rebuilt or serviced with basic tools.

  • Long Service Life: Many engines remain in service after 30–50 years of operation.

  • Quiet and Smooth Operation: Naturally aspirated design reduces turbo whine and vibration.


Additional Resources


Marine Detroit Diesel 6-71 Component Maintenance Life

The Legacy of the Detroit Diesel Marine 671 Engine & Its Use Today

Detroit Diesel 6-71 Marine Engine Specifications (2 Valve, 4 Valve Non-Turbo & Turbo)

The History of the Detroit Diesel 671 Quad Engine Setup

Assembling The Detroit Diesel 671 Long Block

Aftermarket Parts For Detroit Diesel 671 Engines

Everything You Need to Know About the Detroit Diesel 671 Blower

Practical Guide To Servicing Your Detroit Diesel 71 Series Inline (271, 371, 471, & 671 ) – Part 1

Engine Components and Their Roles (Covering Detroit Diesel 271, 371, 471, 671 Engines)

Key Maintenance Procedures (Covering Detroit Diesel 271, 371, 471, 671 Engines)

Assembly and Disassembly Guidelines (Covering Detroit Diesel 271, 371, 471, 671 Engines)

Safety Protocols for Technicians (Working On Detroit Diesel 271, 371, 471, 671 Engines)

Torque Specifications And Wear Limits (Covering Detroit Diesel 271, 371, 471, 671 Engines)

AIR SCAVENGING AND BLOWER SYSTEM FOR DETROIT DIESEL 71 SERIES INLINE ENGINES (271, 371, 471, 671)
Best Practices for Keeping Air Intake and Exhaust Systems Clean For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)
Cleaning and Inspection Processes For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)
Safe Cleaning Procedures Detroit Diesel 71 Series Inline Engine (271, 371, 471, 671)
Critical Inspection Points For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)
Valve and Injector Maintenance For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)
Checking Valve Clearance and Injector Timing For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)
Tools and Equipment For Maintaining Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)
Detailed Overhaul Process For Detroit Diesel 71 Series Inline Engine (271, 371, 471, 671)
Common Troubleshooting Tips For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)
Disassembly Of Fuel Lines For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)
Disassembly Of Exhaust Manifold For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Disassembly Of Throttle Controls For Detroit Diesel 71 Series Inline Engine (271, 371, 471, 671)

Disassembling The Starting Motor, Battery-Charging Generator, and Electrical Equipment For Series 71 Inline Engines (271, 371, 471, 671)

DISASSEMBLY OF AIR COMPRESSOR (IF USED) FOR DETROIT DIESEL 71 SERIES INLINE ENGINES (271, 371, 471, 671)

Disassembly Of The Radiator and Fan Guard or Heat Exchanger For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

DISASSEMBLY OF AIR BOX COVERS FOR DETROIT DIESEL 71 SERIES INLINE ENGINES (271, 371, 471, 671)

Disassembly Of Cylinder Head and Valves For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Disassembly Of Governor Control Assembly For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Disassembly Of Water Pump and Coolant System Components (Freshwater and Raw Water Pumps) For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Disassembly Of The Blower For Detroit Diesel 71 Series Inline Engine (271, 371, 471, 671)

Disassembly Of Blower Drive Gear and Support Assembly For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Disassembly Of The Camshaft and Balance Shaft For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Disassembly Of Flywheel and Flywheel Housing For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

DISASSEMBLY OF THE OIL SYSTEM COMPONENTS FOR DETROIT DIESEL 71 SERIES INLINE ENGINES (271, 371, 471, 671)

Disassembly Of Cylinder Block End Plates For Detroit Diesel 71 Series Inline Engine (271, 371, 471, 671)

Removing Air Box Drains For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Disassembly Of Engine Lifter Brackets For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

REMOVING THE VALVE ROCKER COVER ON A DETROIT DIESEL 71 SERIES INLINE ENGINE (271, 371, 471, 671)

Disassembling The Air Cleaner & The Air Shutdown Housing For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Detailed Guidance on How to Properly Reassemble Components For Series 71 Inline Engines (271, 371, 471, 671)

Torque Specifications Of 71 Series Inline Engines (271, 371, 471, 671)

Recommended Sealants and Techniques to Prevent Leaks After Assembly For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Disassembly Of Components For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Function and Operation of the Oil Pump For Detroit Diesel 71 Series Inline Engine (271, 371, 471, 671)

Key Components of the Oil Pump and Model-Specific Variations (271, 371, 471, 671)

INSIGHTS FROM THE DETROIT DIESEL 71 SERIES INLINE ENGINE MANUAL VOLUME 2 (271, 371, 471, 671)

LUBRICATION SYSTEM FOR DETROIT DIESEL 71 SERIES INLINE ENGINES (271, 371, 471, 671)

Disassembly of the Oil Pump For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Inspection and Cleaning of Oil Pump Parts For Detroit Diesel 71 Series Inline Engine (271, 371, 471, 671)

Reassembly of the Oil Pump For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Testing and Troubleshooting the Oil Pump For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Preventive Maintenance Tips For Oil Pumps For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Oil Pump Specifications and Clearances For Oil Pumps For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Oil Filters For Detroit Diesel 71 Series Inline Engines (271,371, 471, 671)

LUBRICATING OIL PRESSURE REGULATOR FOR DETROIT DIESEL 71 SERIES INLINE ENGINES (271, 371, 471, 671)

Oil Cooler For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Oil Pan For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Ventilating System for Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Recommended Oil and Maintenance Intervals For Detroit Diesel 71 Series Inline Engine (271, 371, 471, 671)

Oil Pump Maintenance For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Troubleshooting Common Lubrication System Issues For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Introduction to the Cooling System and Heat Exchanger For Detroit Diesel 71 Series Engines (271, 371, 471, 671)

Radiator Cooling For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Cooling System and Heat Exchanger For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Cooling System Configurations For 71 Series Inline Engines (271, 371, 471, 671)

COMPARING RADIATOR AND HEAT EXCHANGER COOLING IN DETROIT DIESEL 71 SERIES INLINE ENGINES (271, 371, 471, 671)

Types of Coolant for Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Considerations for High-Temperature and Freezing Conditions for Your Detroit Diesel 71 Series Inline Engine (271, 371, 471, 671)

Chemicals & Coolant For Your Detroit Diesel 71 Series Inline Engine (271, 371, 471, 671)

Filling and Bleeding the Cooling System For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Routine Cooling System Checks and Maintenance For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Maintaining The Heat Exchanger Core For Detroit Diesel 71 Series Inline Engine (271, 371, 471, 671)

Guidelines for Coolant For Detroit 71 Series Inline Engines (271, 371, 471, 671)

Troubleshooting Common Cooling System Issues For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

LONG-TERM BENEFITS OF MAINTAINING THE COOLING SYSTEM FOR DETROIT DIESEL 71 SERIES INLINE ENGINES (271, 371, 471, 671)

Introduction to the Water Pump System for the 71 Series Inline Engine (271, 371, 471, 671)

Disassembly of the Freshwater Pump For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Reassembly of the Freshwater Pump For Detroit Diesel 71 Series Inline (271, 371, 471, 671)

Freshwater Pump Maintenance For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Raw Water Pump Maintenance (Marine Application) For 71 Series Inline Engines (271, 371, 471, 671)

Disassembly of the Raw Water Pump For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Reassembly of the Raw Water Pump For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Importance of Regular Freshwater and Raw Water Pump Maintenance For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Water Pump For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Thermostat Operation For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Ventilation and Crankcase Vapor Collection For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Troubleshooting and Specifications For Cooling & Lubrication In Detroit Diesel 71 Series Inline (271, 371, 471, 671)

Overview of Troubleshooting in Lubrication and Cooling Systems In Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

SYSTEMATIC APPROACH TO TROUBLESHOOTING DETROIT DIESEL 71 SERIES INLINE ENGINES (271, 371, 471, 671)

Cooling System Troubleshooting For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Torque Specifications for Key Components In The Lubrication & Cooling Systems Of Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Parts Grading and Condition Assessment For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

Troubleshooting Tips for Improved Efficiency In Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)
Summary of Troubleshooting and Specifications In Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)

 

Detroit Diesel 271,371,471,671 Inline Engine Tune Up Guide

FAQ From Detroit Diesel 71 Series Inline Engine Service Manual (271, 371, 471, 671) 

 

Disassembly Turbocharger (If Equipped) For Detroit Diesel 71 Series Inline Engines (471, 671)

Disassembly Of Turbochargers For Detroit Diesel 71 Series Inline Engines – (471, 671)


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