Ford 400 V8 (6.6L) Engine

The Ford 400 V8 (6.6L) Engine

Ford 400 V8 Engine Specifications

• Engine Family: 335 Series (same as the 351 Cleveland and 351M)
• Displacement: 400 cubic inches (6.6 liters)
• Bore: 4.00 inches (101.6 mm)
• Stroke: 4.00 inches (101.6 mm)
• Compression Ratio:
  • Early Models (1971-1972): 9.2:1
  • Later Models (1973-1982): 8.4:1 or lower
• Cylinder Configuration: V8
• Valve Configuration: OHV (Overhead Valve), 2 valves per cylinder
• Block Material: Cast iron
• Head Material: Cast iron
• Fuel System: Carburetor (2-barrel and 4-barrel depending on the application)
• Horsepower:
  • Early Models (1971-1972): 260 hp @ 4,600 rpm
  • Later Models (1973-1982): 150-170 hp @ 3,800 rpm (due to emissions regulations)
• Torque:
  • Early Models (1971-1972): 380 lb-ft @ 2,600 rpm
  • Later Models (1973-1982): 270-290 lb-ft @ 2,200 rpm
• Main Bearing Caps: 2-bolt main
• Oil Capacity: 5 quarts (with filter)
• Cooling System Capacity: Approximately 20-21 quarts

Notable Features:

• Block Design: The 400 was designed with a “tall-deck” block to accommodate its long stroke, allowing for the use of longer connecting rods.
• Unique Stroke: The 400 was the only member of the 335 engine family with a square bore and stroke (both 4.00 inches), which provided good torque characteristics, particularly at lower RPMs.
• Emissions Controls: As emissions regulations became stricter in the 1970s, the 400’s compression ratio and power output were reduced to meet these requirements, leading to a decrease in horsepower and torque in later models.

Applications:

• Ford Vehicles:
  • Ford LTD (1971-1979)
  • Ford Thunderbird (1972-1976)
  • Ford Torino (1972-1976)
  • Ford F-Series Trucks (1975-1982)
  • Ford Bronco (1978-1982)
  • Ford Ranchero (1972-1979)
• Mercury Vehicles:
  • Mercury Marquis (1971-1978)
  • Mercury Cougar (1974-1976)
  • Mercury Montego (1972-1976)

Summary:

The Ford 400 V8 was designed to provide strong low-end torque for larger vehicles, making it a reliable choice for towing and heavy-duty applications. However, as emissions regulations tightened, the engine’s performance was significantly reduced in later years. Despite this, the 400 V8 remains a notable part of Ford’s engine history, particularly in its role as a durable workhorse for trucks and large passenger cars.

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Ford 400 6.6L History

The Ford 400 V8 engine, part of Ford’s 335 engine family, was introduced in 1971 in response to the growing demand for engines that could balance performance with the emerging need for greater fuel efficiency and emissions control. The 400 was designed to be a larger, torque-oriented engine, filling the gap between the smaller 351 Cleveland and the more powerful big-block engines. With its unique square bore and stroke design of 4.00 inches each, the 400 was tailored to provide substantial low-end torque, making it well-suited for Ford’s larger cars and light trucks.

Early Years (1971-1972):

In its initial years, the 400 V8 was used primarily in Ford’s full-size cars like the LTD, Thunderbird, and Mercury Marquis. The early versions of the engine featured a relatively high compression ratio of 9.2:1, which allowed it to produce up to 260 horsepower and 380 lb-ft of torque. This made the 400 a strong performer, especially in the context of its intended applications, such as towing and heavy-duty driving.

Mid-1970s and Emissions Regulations:

As the 1970s progressed, the automotive industry faced increasingly stringent emissions regulations, and the Ford 400 was no exception. To comply with these new standards, Ford lowered the compression ratio of the 400, which, in turn, reduced its horsepower and torque output. By the mid-1970s, the 400 was producing between 150 and 170 horsepower and around 270 to 290 lb-ft of torque. Despite the reduced power, the 400 remained popular due to its durability and reliability, especially in truck applications.

Later Years (1975-1982):

The Ford 400 V8 found its way into the F-Series trucks and the Ford Bronco starting in 1975, solidifying its role as a workhorse engine for heavy-duty applications. During this period, the 400 became known for its strong low-end torque, which made it ideal for towing and off-road use. However, the performance limitations imposed by emissions regulations, along with the engine’s relatively heavy weight, made it less appealing for performance enthusiasts.

End of Production:

The Ford 400 V8 was phased out after the 1982 model year, as Ford transitioned to more modern engines that could better meet the changing demands of fuel efficiency and emissions control. Despite its relatively short production run, the 400 left a lasting impact, particularly among those who appreciated its ability to handle tough jobs with ease. Today, the Ford 400 V8 is remembered as a reliable and robust engine, though one more suited to heavy-duty tasks than high-performance driving.

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Ford 400 V8 6.6L Transmission Pairings

The Ford 400 V8 engine was paired with several transmissions over its production run, depending on the vehicle and application. Here are the transmissions commonly used behind the Ford 400:

Manual Transmissions:

1. Ford Toploader 4-Speed Manual
   • Type: 4-speed manual transmission
   • Application: Primarily used in high-performance cars and some trucks in the early 1970s.
   • Notes: The Toploader is known for its strength and was occasionally paired with the 400 in performance-oriented or heavy-duty applications.
2. Tremec (Ford) NP435
   • Type: 4-speed manual transmission
   • Application: Used in Ford F-Series trucks and other heavy-duty vehicles.
   • Notes: The NP435 is a heavy-duty transmission with a low first gear, making it well-suited for towing and off-road use.

Automatic Transmissions:

1. C6 Automatic Transmission
   • Type: 3-speed automatic transmission
   • Application: The most common transmission paired with the Ford 400, used in full-size cars, F-Series trucks, and the Ford Bronco.
   • Notes: The C6 is a heavy-duty transmission designed to handle high torque loads, making it a perfect match for the 400’s torque-oriented design. It was widely regarded for its durability and reliability, especially in trucks and large cars.
2. FMX Automatic Transmission
   • Type: 3-speed automatic transmission
   • Application: Used in some full-size cars during the early 1970s.
   • Notes: The FMX was a medium-duty transmission, known for its durability but was less common with the 400 compared to the C6.

Summary:

The Ford 400 V8 was typically paired with the C6 automatic transmission, especially in trucks and larger cars where its torque characteristics could be fully utilized. The NP435 manual transmission was also a common choice in trucks, offering a strong and durable option for those needing manual control in heavy-duty applications. The FMX, while less common, was also used in some car applications with the 400.

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Modification and Engine Building With the 6.6L 400 V8 Engine

The Ford 400 V8 can be a suitable platform for modification and performance engine building, but it comes with some considerations. Here’s an overview of the pros and cons:

Pros:

1. Strong Bottom-End Torque: The 400’s square bore and stroke design (4.00 inches each) provides excellent low-end torque, making it a good candidate for applications that require strong pulling power, such as towing or off-road use.
2. Durable Block: The cast iron block is robust and can handle increased power with the right modifications. The tall-deck design also allows for the use of longer connecting rods, which can be advantageous in performance builds.
3. Aftermarket Support: There is a moderate level of aftermarket support for the 400, with available performance parts such as camshafts, intake manifolds, and headers. With the right components, the 400 can be built into a strong performer.
4. Interchangeability: The 400 shares many components with the 351M and 351 Cleveland engines, which can provide more options for performance upgrades and parts interchangeability.

Cons:

1. Low Compression Ratio: The stock compression ratio, particularly in later models, is quite low (around 8.4:1 or lower). To achieve significant performance gains, you may need to increase the compression ratio, which could involve changing pistons or milling the heads.
2. Heavy Weight: The 400 is relatively heavy compared to other small-block engines, which might not be ideal for certain performance applications where weight is a concern.
3. Limited High-End Power: The engine was designed with low-end torque in mind, so achieving high RPM power requires significant modification, including camshaft changes, better-flowing heads, and an improved induction system.
4. Emissions Era Design: The 400 was produced during an era when emissions regulations heavily influenced engine design, leading to reduced performance in stock form. Overcoming these limitations in a performance build can be challenging.

Summary:

The Ford 400 V8 can be a viable platform for a performance build, especially if your focus is on low-end torque and heavy-duty applications. However, it requires considerable modification to overcome its stock limitations, particularly in terms of compression ratio and high-end power. With the right upgrades and tuning, the 400 can deliver solid performance, but it’s often overshadowed by other Ford engines, like the 351 Windsor, that are easier to modify for high-performance purposes.

More information on the Ford 400 V8 6.6L engine is available on Wikipedia.

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