Willys Hurricane Engine Explained

The Willys Hurricane engine is a name that resonates with automotive history, particularly for fans of classic Jeeps and Willys vehicles. Born from a lineage of robust and reliable powerplants, the Hurricane represented a significant evolution in engine design for its time. Unlike the modern, electronically managed engines we see today, the Hurricane was a testament to mechanical ingenuity, focusing on improved airflow, higher compression, and enhanced performance. This article delves into the various facets of the Willys Hurricane engine, exploring its origins, its different iterations, and what made it a cornerstone of Willys-Overland's success.

The Genesis: From Go-Devil to Hurricane

The Willys Hurricane engine was not conceived in a vacuum; it was a direct descendant of the earlier Go-Devil flathead engine. The Go-Devil, while a capable unit, had its limitations. To extract more power and efficiency, Willys engineers made a crucial modification: they transitioned the induction system from the Go-Devil's side-valve configuration to an inlet-over-exhaust (IOE) setup, commonly known as an "F-head" design. This architectural change was pivotal. By placing the intake valve above the exhaust valve, the Hurricane allowed for larger valves and a more compact combustion chamber. The benefits were immediate and significant: improved airflow into the cylinders and an increased compression ratio. The compression ratio in the Hurricane saw an increase from the Go-Devil's 6.5:1 to a more potent 7.5:1, although a slightly lower 6.9:1 compression ratio version was also produced. This seemingly simple change in valve arrangement fundamentally boosted the engine's breathing capabilities and, consequently, its power output.

Understanding the F-Head Configuration

The "F-head" moniker describes the physical arrangement of the valves within the cylinder head. In an F-head engine, both the intake and exhaust valves are located on the same side of the cylinder block. However, the intake valve is positioned directly above the exhaust valve, creating an "F" shape when viewed in cross-section. This design offered several advantages over traditional flathead (L-head) designs where both valves were side-by-side:

• Larger Valves: The F-head layout allowed for larger intake valves compared to a similarly sized L-head engine. Larger valves mean more air and fuel can enter the cylinder during the intake stroke, leading to better volumetric efficiency and potentially more power.
• Improved Combustion Chamber Shape: The placement of the intake valve above the exhaust could lead to a more compact and efficient combustion chamber shape, promoting better fuel atomisation and a more complete burn.
• Enhanced Airflow: The design facilitated a more direct and less restrictive flow of the air-fuel mixture into the cylinder.

While the F-head design offered these benefits, it also presented its own set of engineering challenges, particularly in terms of cooling and valve train complexity. Nevertheless, for its era, it was a sophisticated approach to maximising the performance of a relatively simple engine block.

Key Willys Hurricane Variants

The Willys Hurricane wasn't a single, static engine; it evolved over time and across different applications. Here are some of the notable variants:

The F134 Hurricane

The F134 is perhaps the most iconic iteration of the Hurricane engine, closely associated with the post-war Jeep CJ models. While specific details about the F134 itself are less prominent in the provided text, it represents the continuation and refinement of the F-head principle in a compact, versatile package that powered the legendary Jeep.

The F161 Hurricane

The F161 designation refers to a family of F-head engines, often based on the L6-161 Lightning flathead straight-six. These engines offered increased displacement and power, finding their way into various Willys vehicles, including the Model 685 Station Wagon.

BF-161: A Closer Look

The BF-161 is a specific variant within the F161 family. It featured:

• Bore: 3+1⁄8 inches
• Stroke: 3+1⁄2 inches
• Carburetion: One-barrel carburetor
• Power Output: 90 hp (67 kW; 91 PS) at 4400 rpm
• Torque: 135 lb⋅ft (183 N⋅m) at 2000 rpm
• Displacement: 161.1 cu in (2,640 cc)
• Compression Ratio: 7.6:1

The Brazilian Connection: 2600 and 3000 Engines

Willys-Overland's subsidiary in Brazil produced its own versions of the Hurricane engine, notably the 2600 and 3000. These engines showcased adaptations for the local market and evolving automotive trends:

• The 2600: Essentially the BF-161 engine manufactured in Brazil. The key difference was the adoption of dual one-barrel carburetors (operating simultaneously). This modification boosted the power output significantly to 130 hp (97 kW; 132 PS) at 4400 rpm and 140 lb⋅ft (190 N⋅m) of torque at 2000 rpm, while maintaining the 7.6:1 compression ratio.
• The 3000: This version increased the stroke to 4 inches (101.6 mm), resulting in a displacement of 3,016.5 cc (184.1 cu in). Coupled with a two-barrel carburetor, it produced 140 hp (104 kW; 142 PS) at 4400 rpm and 161 lb⋅ft (218 N⋅m) of torque at 2000 rpm. The compression ratio was further enhanced to 8:1. Early versions featured a removable intake manifold, but post-Ford acquisition, they reverted to an integral design. Ford also implemented improvements like enhanced cooling between cylinders 5 and 6 and a side-mounted oil filter.

These Brazilian-built engines powered a range of vehicles, including the Willys Aero, Jeep and Rural Willys, Willys Itamaraty, and even the six-cylinder version of the Ford Maverick in Brazil.

The "Super Hurricane" (6-226)

Distinct from the F-head Hurricane variants, the "Super Hurricane" was a different engine altogether, though it shared the Willys nameplate. This was a 6-cylinder L-head engine sourced from Continental Motors. Key specifications included:

• Engine Type: L-head 6-cylinder
• Manufacturer: Continental
• Bore: 3+5⁄16 inches
• Stroke: 4+3⁄8 inches
• Displacement: 226.2 cu in (3,707 cc)
• Power Output: 105 hp (78 kW; 106 PS) at 3600 rpm or 115 hp (86 kW; 117 PS) at 3650 rpm
• Torque: 190 lb⋅ft (258 N⋅m) at 1400 rpm or 1800 rpm (depending on production year)

The Super Hurricane powered vehicles like the 1955 Jeep Willys Utility Wagon, offering a larger displacement and different power characteristics compared to the F-head Hurricanes.

Mitsubishi's Hurricane Legacy

The reach of the Willys Hurricane engine extended beyond American shores. Mitsubishi, under license, produced its own version of the Hurricane starting in 1954, primarily for its license-built Jeeps. This engine was designated the JH4 and produced 69 hp. Mitsubishi further developed this platform, creating overhead-valve diesel versions:

• KE31: A 61 PS (45 kW) overhead-valve diesel variant.
• KE36: An evolution of the KE31, this was a 3.3 L six-cylinder diesel engine with identical internal dimensions, producing 85 PS (63 kW).

These Mitsubishi diesel engines were not only used in Jeeps but also found their way into a variety of light to medium-weight trucks and buses in Japan, showcasing the adaptability of the original Willys design.

The Modern "Hurricane" Turbo Engine

It's important to note that the "Hurricane turbo engine" developed by Stellantis in 2022 for modern Ram, Jeep, and Dodge vehicles, while bearing the same evocative name, is entirely unrelated to the original Willys Hurricane engines. This modern powerplant is a sophisticated, turbocharged inline-6, representing a new era of automotive engineering.

A Glimpse into Engine Rebuilding: The Red Valve Cover Mystery

Discussions about Willys engines often lead to hands-on enthusiasts sharing their experiences. One common topic is the search for replacement engines and the nuances of identifying them. The mention of a "red valve cover" on a Willys truck points to a specific engine that was being considered for a rebuild. While the colour of the valve cover itself isn't a definitive identifier of the engine model, it's often a repaint colour applied during previous maintenance or restoration attempts. The context suggests this "red engine" was a Super Hurricane, identified by its high-elevation head and a modified draft tube on the valve cover, possibly part of an early PCV (Positive Crankcase Ventilation) system. The anecdote highlights the challenges and joys of sourcing and restoring vintage engines, where details like valve cover colour, carburetor type, and even the presence of a skid plate on the oil pan can offer clues to an engine's history and original application.

Willys Hurricane Engine Specifications at a Glance

To summarise the key technical details, here's a comparative look at some of the Hurricane variants:

Frequently Asked Questions

Q1: What was the main advantage of the F-head design in the Willys Hurricane?

A1: The F-head design allowed for larger intake valves and a smaller combustion chamber, leading to improved airflow, better volumetric efficiency, and an increased compression ratio compared to traditional flathead engines.

Q2: Is the modern Stellantis "Hurricane" engine related to the original Willys Hurricane?

A2: No, the modern 3.0-liter turbocharged inline-6 "Hurricane" engine is a completely new design and shares no mechanical relation to the original Willys Hurricane engines from the mid-20th century.

Q3: What is the significance of the "red engine" mentioned in some discussions?

A3: The "red engine" typically refers to a specific Willys vehicle engine, often a Super Hurricane, that a restorer or enthusiast is working on. The colour is usually a repainted engine block or valve cover, and its identification relies on other mechanical details like bore, stroke, and component markings.

Q4: Did Willys only make F-head engines?

A4: No, while the Hurricane was an F-head design, Willys also produced other engine types, including the earlier Go-Devil flathead (L-head) and the Super Hurricane, which was also an L-head design manufactured by Continental.

Q5: Were Willys Hurricane engines used in vehicles other than Jeeps?

A5: Yes, Willys Hurricane engines, particularly the F161 variants and their Brazilian derivatives, were used in Willys Station Wagons, Willys Aero cars, and other Willys-Overland vehicles.

Conclusion

The Willys Hurricane engine stands as a significant piece of automotive engineering history. Its innovative F-head design represented a leap forward in performance for its era, powering a generation of iconic Willys vehicles. From the rugged Jeep to versatile station wagons and cars, the Hurricane's robust construction and adaptable nature cemented its legacy. Understanding its various iterations, from the core F-head concept to the Brazilian adaptations and the distinct Super Hurricane, provides valuable insight into the evolution of engine technology and the enduring appeal of classic Willys automobiles.