Cylinder Head For Detroit Diesel 71 Series Inline Engines: The Heart of 71 Series Inline Engine Efficiency

October 25, 2024

Cylinder Head For Detroit Diesel 71 Series Inline Engines (271, 371, 471, 671): The Heart of 71 Series Inline Engine Efficiency

Detroit Diesel 471 Cylinder Head With Valves & Springs

The cylinder head is a critical component in the operation of the Detroit Diesel 71 Series Inline Engines—which include the 271, 371, 471, and 671 models. Its role in housing essential components like the exhaust valves and fuel injectors, as well as managing airflow and cooling, makes it the centerpiece of engine functionality. Proper maintenance and knowledge of the cylinder head’s structure and operation are vital for keeping these engines in good working condition, especially given that the official service manual for these engines is no longer in print.

Cylinder Head Parts Catalog For Detroit Diesel 71 Series Inline Engines

Cylinder Head & Related Parts For Detroit Diesel 271

Cylinder Head & Related Parts For Detroit Diesel 371 Non Turbo 2 Valve

Cylinder Head & Related Parts For Detroit Diesel 371 Non Turbo 4 Valve

Cylinder Head & Related Parts For Detroit Diesel 471 Non Turbo 2 Valve

Cylinder Head & Related Parts For Detroit Diesel 471 Non Turbo 4 Valve

Cylinder Head & Related Parts For Detroit Diesel 471 Turbo

Cylinder Head & Related Parts For Detroit Diesel 671 Non Turbo 2 Valve

Cylinder Head & Related Parts For Detroit Diesel 671 Non Turbo 4 Valve

Cylinder Head & Related Parts For Detroit Diesel 671 Turbo

Key Functions of the Cylinder Head: The cylinder head in the 71 Series inline engines performs several essential functions:

Sealing the Combustion Chamber: It provides a strong seal on top of the cylinder block to contain the high pressures generated during combustion.
Housing for Components: It houses critical components like the exhaust valves, fuel injectors, and the valve operating mechanisms, ensuring precise control over air, fuel, and exhaust flow.
Cooling: Coolant circulates through the cylinder head, preventing it from overheating, particularly around the fuel injectors and exhaust valves, which are exposed to intense heat.
Directing Airflow: In these two-stroke engines, the cylinder head helps regulate the intake of fresh air and the expulsion of exhaust gases, contributing to efficient combustion and engine performance.

Components of the Cylinder Head:

Below is a video of a Cylinder head being installed onto a Detroit Diesel 671.

Exhaust Valves: Each cylinder is equipped with either two or four exhaust valves, depending on the engine model. These valves are designed to release exhaust gases after combustion. The valve heads are heat-treated and precision-ground for proper seating.
Fuel Injectors: These injectors are responsible for spraying the correct amount of fuel into the combustion chamber. They sit inside cooling tubes within the cylinder head to prevent overheating and maintain fuel efficiency.
Valve and Injector Operating Mechanism: Rocker arms, driven by the camshaft through push rods, control the opening and closing of the exhaust valves and the timing of the fuel injectors. This ensures that air, fuel, and exhaust are properly managed for efficient combustion.
Valve Seat Inserts: These are pressed into the cylinder head where the exhaust valves seat. They ensure the valves seat properly, even under extreme temperatures and conditions, prolonging the life of both the valve and the cylinder head.
Injector Tubes: Thin-walled tubes pass through the coolant space in the head, protecting the injectors and preventing the cooling water from leaking into the combustion chamber.
Water Nozzles and Coolant Passages: Water nozzles are positioned to direct coolant flow towards the hottest areas around the injectors and valves, ensuring efficient cooling during engine operation.
Manifolds: The fuel inlet and outlet manifolds are cast as part of the cylinder head, allowing direct fuel delivery to the injectors.
Compression Gaskets & Seals: The cylinder head is sealed to the block with laminated metal gaskets at each cylinder, while rubber seals are used for water and oil passages to prevent leaks.

Critical Tolerances & Measurements:

Valve Clearances: The correct valve clearance is essential for optimal engine performance. The exact clearance specifications vary between engine models but typically range from 0.015 to 0.025 inches. If these tolerances are off, it can lead to inefficient combustion, poor engine performance, and potential damage.
Flatness of the Cylinder Head’s Fire Deck: The fire deck—the surface that contacts the cylinder block—must remain flat to ensure a tight seal. Maximum allowable warpage for the fire deck is:
- 3-cylinder models: .005 inches
- 6-cylinder models: .010 inches Warpage beyond these limits can result in compression loss or coolant and oil mixing.
Injector Tube Fitment: The injector tubes must be securely seated and flared at the lower end, with the upper end sealed with a neoprene seal. Loose or damaged injector tubes can lead to serious engine problems such as leaks in the cooling system or poor combustion.
Valve Seat Alignment: The valve seat inserts must remain properly aligned with no excessive wear or gaps, ensuring the valves seat tightly to avoid exhaust gas leakage.

Inspection & Maintenance:

Regular Valve Adjustment: Adjusting the exhaust valve clearance regularly is critical. Incorrect valve clearance can cause the engine to lose power, overheat, or even damage valves.
Cooling System Maintenance: The cylinder head’s cooling passages must remain free of blockages. Scale or debris can reduce the flow of coolant, leading to overheating. It’s important to clean the coolant passages and inspect the water nozzles during routine maintenance.
Injector Tube Inspection: Check the injector tubes for wear or signs of leakage, as leaking tubes can allow coolant or combustion gases into the fuel system, causing severe engine issues.
Gasket and Seal Inspection: The cylinder head gaskets and seals between the head and the block should be checked during any major service. A failed gasket can lead to compression leaks, oil in the coolant, or coolant in the oil, which can quickly damage the engine.
Check for Cracks or Warping: Overheating is a common cause of cylinder head damage, which may lead to cracking or warping of the head. The presence of melted fuse plugs (located on the exhaust side of the head) is a sign that the engine has overheated and requires thorough inspection.

Common Symptoms of Cylinder Head Problems:

Overheating: An overheating engine, especially around the cylinder head area, may indicate blockages in the cooling passages or damage to the cylinder head itself. A melted fuse plug often points to this issue.
Loss of Compression: If the engine is underperforming or losing power, it could be due to poor valve seating, damaged injector tubes, or failing gaskets, all leading to loss of compression.
Coolant in Oil or Oil in Coolant: This is a clear sign of a blown head gasket or cracked cylinder head. This issue can quickly escalate and cause major damage to engine components if not addressed immediately.
Excessive Exhaust Smoke: Black smoke from the exhaust can indicate poor combustion, which is often a result of worn or poorly seated exhaust valves.
Sticking Valves: Carbon buildup, often caused by improper combustion, can cause exhaust valves to stick. This may lead to poor engine performance and even cause valves to bend if not addressed promptly.

Conclusion To The Cylinder Head Section:

The cylinder head is one of the most important components of the Detroit Diesel 71 Series Inline Engines, including the 271, 371, 471, and 671 models. Understanding its key functions, the critical components it houses, and the maintenance it requires is essential for any owner or mechanic working with these engines. By keeping the cylinder head in good condition—through proper valve adjustments, cooling system maintenance, and timely inspections—you can extend the engine’s lifespan and maintain optimal performance. Given that the original service manuals are no longer in print, this guide serves as a vital resource to keep your engine running smoothly and efficiently.