Installing The Injectors & Fuel Lines On A Detroit Diesel 671 Video

March 25, 2025

Installing The Injectors & Fuel Lines on a Detroit Diesel 671 | Long Block Build In this video, the technicians demonstrate the installation of injectors and fuel lines on a Detroit Diesel 671 as part of a long-block engine build. This behind-the-scenes footage offers a real-world look at how experienced professionals perform these critical steps in the assembly of one of Detroit Diesel’s most iconic two-stroke engines.

The Detroit Diesel 6-71 is renowned for its durability, simplicity, and performance in marine, industrial, and on-highway applications. Proper installation of the injectors and fuel lines is essential not only for delivering the right amount of fuel to each cylinder but also for ensuring the overall reliability and efficiency of the engine.

This video is an excellent visual resource for anyone working on a 6-71 engine, whether you’re performing a full rebuild, replacing components, or simply gaining familiarity with the injector and fuel system layout. You’ll see how our technicians approach each connection with care, ensuring proper fit, alignment, and cleanliness throughout the process.

What You’ll See:

-Injector alignment and seating during long block assembly
-Proper handling and orientation of fuel lines
-Tips for a clean and secure installation to avoid leaks or misfires
-Visual reference for engine layout and component locations

This video doesn’t include torque specs or calibration steps, so if you’re planning to perform this work yourself, we highly recommend using it in combination with the official Detroit Diesel service manual. The manual includes the exact torque values, adjustment procedures, and safety checks needed for a complete and precise installation.

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Injectors For Detroit Diesel 671 Engines

Injectors for Detroit Diesel 6-71 engines play a critical role in delivering the precise amount of fuel required for efficient combustion across a variety of configurations, including non-turbocharged 2-valve and 4-valve cylinder heads, as well as turbocharged variants. In naturally aspirated 2-valve engines, injectors are typically smaller—ranging from 40 to 55 mm in fuel delivery rating—suited for steady-state applications such as generators, marine auxiliaries, and industrial equipment. The 4-valve head design allows for improved airflow, supporting slightly larger injectors that enhance throttle response and combustion efficiency. Turbocharged 6-71 engines, often used in high-performance or marine propulsion settings, utilize higher-capacity injectors (typically 65 to 80 mm or more) to match the increased air volume delivered by the turbo system. Proper injector selection and calibration are essential for maintaining balanced fuel delivery, maximizing power output, and preventing issues such as excessive smoke or uneven cylinder performance. Regular inspection and maintenance of these unit injectors—including nozzle cleaning, follower adjustment, and cam timing—ensure optimal engine performance across all 6-71 configurations.

Injectors For Detroit Diesel 6-71 Non Turbo 2-Valve Engines

Injectors For Detroit Diesel 6-71 Non Turbo 4-Valve Engines

Injectors For Detroit Diesel 6-71 Turbo Engines

Fuel Lines For Detroit Diesel 671 Engines

Fuel lines on Detroit Diesel 6-71 engines are essential for transporting fuel from the supply manifold to the unit injectors, and they vary in length depending on engine configuration and cylinder head design. These engines use both long and short fuel lines to accommodate the injector layout—particularly in 2-valve versus 4-valve heads and in turbo versus naturally aspirated variants. On standard 2-valve heads, typically found on naturally aspirated engines, the injector ports are positioned in a way that requires shorter fuel lines due to the more compact layout and limited airflow channels. In contrast, 4-valve heads—which offer improved breathing and increased injector spacing—often use a combination of short and long fuel lines to accommodate the staggered injector port geometry. Turbocharged 6-71 engines, especially those with rear or top-mounted fuel manifolds, may also require longer fuel lines to reach rearward or elevated injectors. Proper routing and secure clamping of these fuel lines are critical to avoid vibration fatigue, leaks, or pressure drops, especially in high-RPM or marine environments. Always replace fuel lines with the correct length and fitting style for your specific head and injector setup to maintain fuel delivery consistency and engine reliability.

Fuel Lines For Detroit Diesel 6-71 Non Turbo 2-Valve Engines

Fuel Lines For Detroit Diesel 6-71 Non Turbo 4-Valve Engines

Fuel Lines For Detroit Diesel 6-71 Turbo Engines

Socket To Install & Remove Injector Fuel Lines For Detroit Diesel 53 — Socket To Install & Remove Injector Fuel Lines For Detroit Diesel 71 Series Engines

New Style Few Lines For Detroit Diesel 671 Engines

New Style Fuel Line For Detroit Diesel 671

The new-style fuel lines for Detroit Diesel 6-71 engines feature several improvements over older designs, offering enhanced reliability, better sealing, and easier installation. These updated lines typically use precision-formed steel tubing with upgraded flared ends and threaded fittings that reduce the risk of leaks under high fuel pressure. Unlike older lines that relied on compression-type fittings, the new-style lines often incorporate improved vibration resistance and are designed to maintain a consistent fuel path with minimal flow restriction. Additionally, the layout and bending profiles are optimized to prevent rubbing against engine components, which was a common issue with legacy fuel lines. These modern fuel lines are particularly beneficial in high-demand applications like marine propulsion and heavy-duty trucks, where consistent fuel delivery and durability under vibration are critical for long-term engine performance.