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Parts for Detroit Diesel 671 Non-Turbo - (2 Valve Head Type)

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Free - Detroit 6-71 Troubleshooting Guide

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.