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. 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: 4.25 inches (108 mm) Stroke: 5.00 inches (127 mm) 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 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 Dry Weight (Base Engine): ~2,185 lbs (991 kg) Length: ~67 inches (170 cm) Width: ~30 inches (76 cm) Height: ~40 inches (102 cm) 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. 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. 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. 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. This engine was designed with marine use in mind and has seen decades of service across commercial and recreational fleets. 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. 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. 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. 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. Marine Detroit Diesel 6-71 Component Maintenance Life 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) Disassembly Of Throttle Controls For Detroit Diesel 71 Series Inline Engine (271, 371, 471, 671) DISASSEMBLY OF AIR BOX COVERS 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) Removing Air Box Drains 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) Torque Specifications Of 71 Series Inline Engines (271, 371, 471, 671) Disassembly Of Components For Detroit Diesel 71 Series Inline Engines (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) Reassembly of the Oil Pump 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) Oil Pump Maintenance For Detroit Diesel 71 Series Inline 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) Types of Coolant for Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671) Chemicals & Coolant For Your Detroit Diesel 71 Series Inline Engine (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) 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) 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) 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) Troubleshooting Tips for Improved Efficiency In Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671)  Detroit Diesel 271,371,471,671 Inline Engine Tune Up Guide  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)
Parts for Detroit Diesel 671 Non-Turbo - (2 Valve Head Type)
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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
Technical Specifications of the Detroit Diesel 671 Non-Turbo 2-Valve Engine
Core Engine Specs
Bore and Stroke
Performance and Power
Oil & Cooling System Capacities
Engine Dimensions and Weight
Key Features of the 671 Non-Turbo 2-Valve Engine
Simple and Reliable
Modular Cylinder Heads
High Low-End Torque
Cold Weather Performance
Marine Applications of the Detroit Diesel 671 Non-Turbo 2-Valve
Recreational Marine Use
Commercial Marine Use
Industrial Applications of the Detroit 671 2-Valve Engine
Why Mechanics and Fleet Operators Still Choose the 671 Non-Turbo 2-Valve
Additional Resources
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
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)
Disassembling The Air Cleaner & The Air Shutdown Housing For 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)
FAQ From Detroit Diesel 71 Series Inline Engine Service Manual (271, 371, 471, 671)Â