351W to Cleveland Engine Swaps: A Comprehensive Guide

Embarking on a Ford engine swap can be an exhilarating project, breathing new life into classic machinery. One such conversion that often sparks discussion is the integration of a 351 Windsor (351W) engine into a vehicle originally equipped with a Cleveland engine. While both are legendary Ford V8s, the process isn't as straightforward as a direct bolt-in. This guide delves into the nuances, focusing on critical components like intake manifolds and cylinder heads, and offers insights into optimising performance for your street or strip machine.

Understanding the 351W and Cleveland Architectures

Before diving into the specifics of the swap, it's crucial to appreciate the fundamental differences between the 351 Windsor and the 351 Cleveland. The Windsor, produced from 1969 to 1996, shares its basic architecture with the smaller 289/302 Windsor engines, featuring a narrower deck width and different bellhousing bolt patterns. The Cleveland, produced from 1970 to 1974, was Ford's performance-oriented big-block (despite its 351 cubic inch displacement), known for its robust block, larger main bearings, and distinctive canted-valve cylinder heads.

The primary challenge in fitting a 351W into a Cleveland chassis lies in the physical dimensions and mounting points. While displacement is similar, the Windsor's block is physically narrower, and its accessory drive systems and exhaust manifolds may require modification or custom fabrication to fit correctly. However, the real expertise often comes into play when discussing the engine's breathing apparatus – the intake manifold and cylinder heads.

Intake Manifolds: Single Plane vs. Dual Plane Dilemmas

A significant point of contention and discussion among Ford enthusiasts revolves around the choice of intake manifold. The user's preference against single-plane manifolds for street engines is a common sentiment, often rooted in the perception that they prioritise high-RPM power at the expense of low-end torque and drivability. Let's dissect this:

The Dual Plane Advantage (for the Street)

Dual-plane manifolds, like the Edelbrock Performer series, are generally favoured for street applications. They are designed to enhance low-to-mid range torque and throttle response, making the vehicle more tractable in everyday driving. The "dual plane" design typically routes intake runners in a way that promotes better cylinder filling at lower engine speeds, creating a more potent torque curve.

The Single Plane Argument (for Performance)

Single-plane manifolds, on the other hand, feature a unified plenum with all runners entering from a central point. This design is often associated with maximising horsepower at higher RPMs and extending the engine's powerband. The theory is that at higher engine speeds, the increased airflow and the lack of plenum "restrictions" allow the engine to breathe more freely, leading to significant gains in peak horsepower.

Dyno Results and Real-World Observations

The provided text offers compelling real-world dyno data that challenges conventional wisdom. In one instance, a 393C (a stroked Cleveland) equipped with ported Aussie 2V heads was tested with various intake manifolds. The results were surprising:

These results suggest that for certain combinations of cubic inches, port size, and compression, the velocity within the intake ports is already high enough that the dual-plane plenum effect is not only unnecessary but can actually act as a restriction. The single-plane manifolds consistently outperformed the dual-plane Air Gap, even at lower RPMs like 2500. This data highlights that the "rule of thumb" regarding single vs. dual plane manifolds isn't always absolute and depends heavily on the specific engine combination.

Factors influencing this outcome include:

• Cubic Inches: Larger displacement engines generally move more air, potentially negating the low-end benefits of a dual-plane manifold.
• Port Size and Shape: Larger or "high port" heads can benefit from manifolds that can supply ample air volume.
• Compression Ratio: Higher compression can lead to more efficient combustion and a broader powerband.
• Camshaft Profile: The camshaft's duration, lift, and overlap significantly influence where the engine makes its power.

For a 351W going into a Cleveland chassis, if you're aiming for a performance-oriented build, investigating single-plane options like the Holley Street Dominator or Weiand Xcelerator might yield surprising results, even on the street. However, for a more traditional, mild build focused on low-end grunt, a well-matched dual-plane manifold remains a solid choice.

Cylinder Heads: The Heart of the Breathing Equation

Cylinder heads play an equally, if not more, crucial role in engine performance. The Cleveland family is renowned for its innovative 4V and 3V heads, featuring larger, canted valves and "high ports" designed for better airflow at higher lifts. The 2V heads, while still capable, are generally considered more "street-oriented" with smaller ports and valves.

2V vs. 4V Heads: A Flow Bench Perspective

The general consensus has been that 2V heads are strictly for street use, while 4V (and 3V, SVO, etc.) heads, with their higher port entries, are better suited for racing due to their superior airflow at higher valve lifts. However, flow bench data suggests a broader advantage for the high-port heads:

• Flow bench work indicates that 3V, 4V, and high-port heads generally outperform 2V heads across the entire lift range, not just at high lifts.

The Rise of the Modern 2V Heads

The landscape of cylinder heads is constantly evolving. The advent of CNC-ported heads has significantly closed the gap between traditional 2V and 4V designs. The new Trick Flow 225 CNC ported 351C-2V heads are a prime example. While Trick Flow advertises a flow rate of 330 cfm, independent testing of the 190 cfm version showed figures of 271 cfm intake and 199 cfm exhaust at 0.600" lift. While not quite matching the advertised numbers, this is still a substantial improvement over stock Edelbrock 351C-2V heads.

Even with these advancements, the 225 CNC 2V heads are still expected to fall short of true high-port heads in peak flow. However, the overall flow characteristic across the entire lift curve is essential for assessing their potential. Some heads might exhibit incredibly strong exhaust ports but only fair intake ports, and with the right camshaft tuning, can still produce impressive power. For instance, Aussie 2V heads, with a flow rate of 220 cfm intake and 200 cfm exhaust, performed remarkably well on a 393C, not being drastically outpaced by a 408C with 4V heads that flowed 322 cfm on the intake side.

Choosing the Right Heads for Your 351W-to-Cleveland Swap

When considering cylinder heads for your 351W in a Cleveland application, ask yourself:

• What is your intended use? Street cruising, autocrossing, drag racing, or a bit of everything?
• What is your budget? High-performance heads, especially aftermarket ones, can be a significant investment.
• Are you willing to modify? Porting stock heads or opting for aftermarket units requires careful consideration.

If you're leaning towards a street performance build and want to retain the Cleveland's characteristic feel, a well-ported set of 2V heads or modern CNC-ported aftermarket 2V heads could be an excellent choice. For maximum performance and a broader powerband, especially if you're considering stroking the 351W or intend to rev the engine high, Cleveland 4V or aftermarket high-port heads would be the preferred route. Remember to match the intake manifold to the heads and the intended RPM range.

Key Considerations for the 351W in Cleveland Swap

Beyond the intake and heads, several other factors are critical for a successful 351W to Cleveland engine swap:

1. Engine Mounts

The physical dimensions of the 351W block differ from the Cleveland. You will likely need custom or adapted engine mounts to ensure proper positioning and alignment within the chassis.

2. Transmission Compatibility

While both engines share some common transmission bolt patterns, it's essential to verify compatibility. The bellhousing bolt pattern on a 351W is typically based on the small-block Windsor pattern, which may differ from the Cleveland's. Adapters might be necessary.

3. Accessory Drives

The front of the 351W engine, including the water pump, power steering, and alternator mounting, might require different brackets or a complete serpentine conversion kit to fit the Cleveland chassis's existing setups.

4. Exhaust Systems

Exhaust manifolds or headers designed for a Cleveland may not align correctly with the exhaust ports of a 351W. You'll likely need to source or fabricate headers specifically for this hybrid setup.

5. Cooling System

Ensure the radiator and cooling fan setup are adequate for the 351W's cooling requirements, which may differ slightly from the original Cleveland.

6. Fuel System

Depending on the performance level of your 351W, you may need to upgrade the fuel pump, lines, and potentially the carburettor to deliver adequate fuel.

Frequently Asked Questions

Q1: Can I bolt a 351W directly into a car that had a 351 Cleveland?A1: No, it's not a direct bolt-in. While they share displacement, physical dimensions, mounting points, and accessory drives differ, requiring modifications or custom parts.

Q2: Which intake manifold is best for a 351W in a Cleveland for street use?A2: For general street use, a dual-plane manifold like the Edelbrock Performer or Performer RPM is often recommended for good low-end torque and drivability. However, as dyno results show, single-plane manifolds can also perform very well, even at lower RPMs, depending on the overall engine combination.

Q3: Are 2V or 4V Cleveland heads better for a 351W swap?A3: For a street-focused build, well-ported 2V heads or modern CNC-ported aftermarket 2V heads can be excellent. For higher performance applications aiming for more RPM and peak horsepower, Cleveland 4V heads or aftermarket high-port heads are generally superior due to their better airflow characteristics.

Q4: What transmission will work with a 351W in a Cleveland chassis?A4: You'll need to ensure your transmission's bellhousing pattern matches the 351W. Adapters may be required if the original Cleveland transmission has a different bolt pattern.

The 351W to Cleveland engine swap is a rewarding project for the enthusiast looking to combine the strengths of two iconic Ford V8s. By carefully considering the intake manifold, cylinder heads, and all the associated mechanicals, you can build a powerful and reliable engine that honours the legacy of both the Windsor and the Cleveland.