Piper 285 & 1700 XFlow: A British Mechanic's Insight

The Ford Crossflow engine, a true icon in British motoring history, continues to power a vast array of vehicles, from classic Fords to numerous kit cars and historic racers. Its enduring popularity stems from its robust design and remarkable tunability. However, when it comes to pushing its performance boundaries, particularly with high-lift camshafts like the Piper 285, enthusiasts often encounter a complex web of engineering challenges and significant financial outlays. This article delves into the intricacies of mating a high-performance camshaft with a 1700cc Crossflow, drawing on real-world experiences to highlight the potential pitfalls and necessary considerations for a successful build.

The question of whether a Piper 285 camshaft can effectively 'drive' a 1700cc Crossflow is not a simple yes or no. The answer is nuanced, heavily dependent on the specific engine build, the existing components, and the willingness to invest in extensive modifications. While the Piper 285 is renowned for its aggressive profile, offering substantial lift and duration for performance gains, installing such a camshaft into a standard or mildly modified 1700 XFlow without proper preparation is highly likely to lead to mechanical failure.

Understanding the Ford Crossflow Engine

Before delving into camshaft compatibility, it's essential to appreciate the Ford Crossflow engine itself. This legendary inline four-cylinder powerplant, originally known as the Kent engine, earned its 'Crossflow' moniker from its cylinder head design, where the inlet and exhaust ports are on opposite sides, allowing for more efficient gas flow compared to earlier 'reverse-flow' designs. From its early pre-Crossflow iterations to the later, more refined versions, it has been a cornerstone of Ford's compact car range and a staple in various forms of motorsport.

Our workshop, for instance, has been building and rebuilding these engines for decades, ranging from 997cc to 2200cc, including carburetted and electronic fuel injection (EFI) versions. Despite its age, the Crossflow remains incredibly popular in Formula Ford, short oval racing, rallying, and circuit racing. Its robust architecture and continued availability of parts, coupled with specialised build and rebuild services, ensure its legacy endures in the classic and motorsport communities.

The Challenge of High-Lift Camshafts: Piper 285 and Beyond

High-performance camshafts, such as the Piper 285, are designed to maximise an engine's volumetric efficiency by increasing valve lift and duration. This means the valves open further and stay open for longer periods, allowing more air-fuel mixture into the combustion chamber and more exhaust gases out. While this is the key to unlocking significant horsepower, it introduces a critical engineering challenge: valve-to-piston clearance.

One real-world account highlights this perfectly. An owner attempting to fit a Kent Fast Road A14 camshaft (a cam with similar performance characteristics to a Piper 285, featuring .385" lift and 286/278-degree duration) into a 1660cc Crossflow encountered immediate problems. Despite assurances that the cam wouldn't interfere with the valves, it did. Even a slight 'kiss' between the valve and the piston was enough to cause significant damage, breaking two valve followers and leaving marks on the piston crowns where the valves made contact. This directly illustrates the severe consequences of inadequate valve clearance.

For a Piper 285 or any high-lift cam to work reliably in a 1700cc Crossflow, several critical modifications are almost certainly required:

• Piston Pocketing: This is arguably the most crucial modification. As demonstrated, even a small amount of contact can be catastrophic. Piston pocketing involves machining small recesses into the piston crowns, creating additional clearance for the valve heads at their maximum lift. Experts often recommend pocketing by a specific depth, such as 0.030 inches, to ensure adequate clearance, especially with larger valves.
• Cylinder Head Modifications: A high-lift cam demands a cylinder head that can flow sufficient air. Owners often upgrade to Stage III heads with larger valves (e.g., 41mm inlet / 36mm exhaust). However, larger valves exacerbate the valve-to-piston clearance issue, making pocketing even more critical. Furthermore, the anecdote reveals that a 'bargain' head on the second-hand market can hide severe issues, such as worn valve shafts and perished seals, leading to further expense.
• Valve Train Components: High-lift cams put immense stress on the valve train. Stronger, high-quality valve followers are essential, as is a robust duplex double cam chain to handle the increased loads and maintain precise timing.

The Financial Realities: A Costly Endeavour

Building a high-performance Crossflow is not for the faint of heart, nor for those on a tight budget. The costs can quickly escalate, turning what might seem like a straightforward upgrade into a significant financial commitment. The owner's experience with the 1660cc Crossflow serves as a stark warning about the costs involved:

• Initial Parts Outlay: A new camshaft, followers, water pump, oil pump, a full Cometic gasket kit, clutch, pressure plate, and release bearing can easily amount to hundreds of pounds. In the cited case, this was around £600.
• Unexpected Repairs: The 'bargain' cylinder head, initially £150, turned into a £750 problem due to worn valve shafts and buggered seals, requiring professional attention. This highlights the risk of second-hand components.
• Further Rebuild Costs: After stripping the engine down due to issues, additional parts were needed, including new piston rings, a vernier pulley for precise cam timing, another set of new followers, and yet another gasket set. These unexpected costs pushed the total expenditure close to £1,000, and that was just for parts, not including significant labour or machining.
• Professional Machining and Balancing: To achieve reliability and performance with a high-lift cam, professional services are indispensable. Balancing the pistons, crankshaft, and connecting rods is crucial for smooth operation and longevity at higher RPMs. This adds significantly to the overall cost.

As the owner aptly put it, "Old Skool - new prices." Achieving even around 120 hp from a highly tuned Crossflow can be a very expensive process.

Supporting Systems and Considerations

Beyond the core engine internals, other systems must be considered when fitting a Piper 285 to a 1700 XFlow:

• Carburetion: With larger valves and increased airflow, the carburettor must be up to the task. A Weber 32/36 DG V5A, while versatile, might not be sufficient to feed a highly tuned engine with 41mm/36mm valves. Upgrading to a larger carburettor, such as a Weber 38 from a V6, might be necessary. This, however, introduces a trade-off between outright performance and fuel economy/simplicity, especially if the car is used for daily commuting.
• Flywheel Lightening: A lightened flywheel (e.g., to 7kg) can improve throttle response and allow the engine to rev more freely, complementing the aggressive cam profile.
• Engine Balancing: As mentioned, balancing the rotating assembly (crankshaft, pistons, connecting rods) is vital for a high-revving, high-performance engine. It reduces vibrations, improves reliability, and allows the engine to safely operate at its peak potential.

Potential Alternatives

Given the significant costs and complexities involved in highly tuning a Crossflow, some enthusiasts consider alternative engine swaps. The Zetec engine, for instance, is often cited as a more modern, potentially more cost-effective, and powerful alternative for kit cars and classic Fords, offering a more straightforward path to higher horsepower with less bespoke machining.

However, for those committed to the classic Crossflow, resources like "Rebuilding and Tuning Ford's Kent Crossflow Engines" by Peter and Valerie Wallage are invaluable guides, offering detailed insights into the nuances of these engines.

Frequently Asked Questions

Q: What exactly is a Ford Crossflow engine?
A: The Ford Crossflow engine, also known as the Kent engine, is an inline four-cylinder internal combustion engine produced by Ford. Its name 'Crossflow' comes from its cylinder head design where the intake and exhaust ports are on opposite sides, allowing for better airflow. It was widely used in Ford cars and various forms of motorsport from the 1960s onwards.

Q: Can I simply drop a Piper 285 cam into my standard 1700 XFlow?
A: No, absolutely not. A Piper 285 is a high-lift, high-duration camshaft that will almost certainly cause valve-to-piston interference in a standard 1700 Crossflow. Extensive modifications, particularly piston pocketing and head work, are required.

Q: What are the main challenges when fitting a high-performance cam like the Piper 285?
A: The primary challenge is ensuring adequate valve-to-piston clearance. Other challenges include sourcing high-quality components, dealing with worn existing parts, ensuring proper carburetion, and managing the significant costs of machining and specialist labour.

Q: How much should I budget for a high-performance 1700 XFlow build with a cam like the Piper 285?
A: Based on experience, you should expect costs to be in the realm of several hundreds to well over a thousand pounds, easily reaching £1,000 or more, especially if unexpected issues arise or professional machining and balancing are factored in. This estimate is for parts and basic repair, not a complete professional build.

Q: Is it worth the cost and effort to highly tune a Crossflow?
A: This depends on your goals. For historical accuracy, the joy of working with a classic engine, or competitive motorsport classes requiring a Crossflow, it can be incredibly rewarding. However, if pure power-per-pound is the objective, modern engine swaps might offer a more cost-effective route.

Conclusion

In conclusion, while a Piper 285 camshaft can indeed 'drive' a 1700cc Ford Crossflow, it is far from a bolt-on upgrade. It necessitates a comprehensive and often costly approach, involving crucial modifications such as piston pocketing, cylinder head work, and supporting system upgrades. The experience of others clearly indicates that cutting corners or underestimating the complexities can lead to significant mechanical failures and escalating costs. For any enthusiast considering such an upgrade, thorough research, consultation with experienced Crossflow engine builders, and a realistic budget are absolutely essential to transform the classic Crossflow into a reliable high-performance unit.

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