Coventry Climax: From Fire Pump to Race-Ready

The Unlikely Racer: Coventry Climax's Journey

In the world of motorsport, engines are typically born from a lineage of performance, either as purpose-built racing units or heavily modified production car powerplants. However, the Coventry Climax engine stands as a remarkable exception. Its genesis lies not on the racetrack, but in a humble beginning as a portable fire pump engine, commissioned by the British government in 1951. Thousands of these all-aluminium, 'Feather Weight' (FW) pump engines served dutifully over the years. Yet, the vision of Coventry Climax's president, Leonard Lee, and chief engineer, Walter Hassan, saw a different destiny for these robust units. They recognised the potential for racing to act as a powerful "halo" for the company, leading to the birth of the Coventry Climax FWA ('Feather Weight Automotive') powerplant.

The FWA made its racing debut at the prestigious 24 Hours of Le Mans in 1954, powering a Kieft Special, driven by none other than Stirling Moss. Initially, this 1098cc engine, with a bore of 2.850 inches and a stroke of 2.625 inches, featured a cast crankshaft, three main journals, and a compression ratio of 9.8:1, producing a modest 71 horsepower. Despite its humble origins, it quickly became the heart of Colin Chapman's legendary Lotus Eleven. A de-stroked variant even clinched the coveted Index of Performance at Le Mans in 1957, showcasing the engine's inherent potential. Later iterations, such as the FWB, were enlarged to 1460cc, boosting output to 108 horsepower, while the FWE found its place powering the Lotus Elite.

Reviving a Legend: Steve Sanett's Pursuit of Power

Fast forward several decades, and the story of the Coventry Climax takes an exciting new turn with the involvement of Steve Sanett. A seasoned competitor with a history of fielding entries in the Indy 500 and Long Beach Grand Prix during the 1980s, Sanett later transitioned to vintage sports car racing. In 2014, he acquired a Lotus Eleven, embarking on a journey of competition at SVRA and VARA events, including the esteemed Rolex Historic Championships at Laguna Seca.

While Sanett's Lotus Eleven proved competitive and secured a few victories, it consistently lacked the raw power of some of the class front-runners. This spurred Sanett to undertake a monumental project for the 2020 season: to build the "ultimate" Coventry Climax engine. The ambitious goal was to create a fire pump engine unlike any other, capable of delivering over 100 horsepower per litre with unwavering reliability. This ambitious undertaking has seen the collaboration with Australian engine builder Doug Pearce, now a vital member of the Penta Motorsports team. Furthermore, the project has leveraged contemporary technology from leading aftermarket component manufacturers in the USA and UK, injecting a significant amount of intellectual firepower into Sanett's Climax build.

The Engineering Marvel: Fortifying the FWA Block

The original FWA block, a lightweight cast-aluminium unit weighing a mere 45 pounds, came equipped with three cast-aluminium main caps. To fortify the bottom end for the rigours of high-performance racing, a set of billet-steel main caps were sourced from England. Doug Pearce, however, took this enhancement a significant step further. He meticulously machined these caps to accommodate 360-degree thrust bearings, repurposed from BMC A-series motors (found in vehicles like the Sprite, Mini, and Midget). This modification provides substantially increased support for the billet crankshaft, expertly manufactured by Marine Crankshaft in Santa Ana, California.

Another crucial upgrade to the block involved the application of Nikasil to the cylinder liners. This advanced process electroplates nickel onto the cylinder walls in the presence of hard particulates, such as Silicon Carbide. Under specific conditions, these hard particles co-deposit with the nickel, creating an exceptionally durable and low-friction surface. For this critical process, Penta Motorsports enlisted the expertise of Millennium Technologies, a renowned industry specialist based in Plymouth, Wisconsin.

Precision Internals: Pistons, Rods, and Bearings

Gliding within the cylinders are specially lightened, forged 2618 aluminium pistons from Diamond Racing Pistons. These pistons feature a carefully designed dome to achieve a compression ratio of 12.5:1. The pistons are fitted with Total Seal rings, including their innovative new gas-ported top rings, designed to enhance sealing under extreme pressure. The connecting rods, manufactured by Pauter Machine of Chula Vista, CA, tip the scales at a precise 457 grams. Complementing these are the Diamond pistons, weighing in at 254 grams, along with 92-gram pins. To ensure smooth and reliable operation, ACL rod and main bearings were selected for their proven performance and durability.

Optimising Lubrication and Bottom-End Strength

Enhancing the lubrication system was a paramount consideration in this build. Doug Pearce fabricated a full-length windage tray, replacing the original, less effective half-sized OEM unit. This improved tray significantly aids in controlling oil splash and pressure. Furthermore, Pearce reinforced the bottom end of the engine by incorporating a 0.250-inch-thick 6061-T6 aluminium plate between the block and the oil pan. This was secured using ARP 8740 chromoly pan studs, adding considerable rigidity to the assembly. The Penta Motorsports crew also designed and fabricated a specialised oil pump housing. This housing accommodates a taller gear, thereby increasing oil volume, and includes an improved oil pick-up for more efficient scavenging.

The Heart of the Matter: A Modified SOHC Top End

The single-overhead camshaft (SOHC) aluminium cylinder head has undergone extensive work. Its combustion chambers now bear a striking resemblance to those found in high-performance aftermarket SBC (Small Block Chevrolet) heads. The intake manifold and ports have been meticulously blended to create a "funnel" effect, designed to enhance airflow velocity and direct the charge precisely at the intake valves. A pair of large Weber DCOE-45 carburetors, equipped with 36mm venturis, are responsible for delivering the optimal air/fuel mixture. Ignition is handled by a Zig-modified Vertex magneto, ensuring a strong and consistent spark.

The valves themselves are a testament to weight reduction: 37mm intake and 34mm exhaust valves, featuring 6mm stems to minimise mass. Special titanium retainers are employed, with individually clearanced lash caps replacing the more common cylindrical "biscuits." The extensive cylinder head preparation was expertly carried out by Valley Head Service in Northridge, CA. The valves are actuated by a bespoke camshaft, ground to Penta's precise specifications by the renowned Kent Cams in the UK. This camshaft is housed within a robust, five-bearing billet machined 6061-T6 support tower, ensuring exceptional stability and longevity. Doug Pearce of Penta also fabricated an adjustable gear drive, a critical component for ensuring optimal timing accuracy throughout the engine's operating range.

For all sealing duties, a Cometic solid copper head gasket was chosen, along with other Cometic gaskets for the oil pan, water pump, and rocker cover, ensuring leak-free performance under demanding conditions.

Putting it to the Test: Dyno Results and Future Prospects

To truly assess the capabilities of Penta's meticulously prepared "Pumper," it was only logical to subject the Coventry Climax to rigorous testing at Huffaker Engineering in California's picturesque wine country. Joe Huffaker Sr., the founder of the company in 1966 and a veritable legend in the sports car community, renowned for designing the highly sought-after Huffaker Genie, along with his son Joe Jr. (who has led the company for over 25 years), possess a wealth of experience with Coventry Climax engines. They have the necessary facilities and expertise to connect the engine to their late-model SuperFlow dynamometer.

The initial objective for this project was to surpass the typical 130-140 horsepower output of a fully prepared Coventry Climax engine, while simultaneously enhancing its reliability, particularly in the upper RPM range. From a power perspective, the dyno session yielded impressive results, with a peak output of 144.8 horsepower achieved at 7,200 RPM. The engine demonstrated a commendably consistent top-end power curve. While this figure was just shy of the ambitious 100-horsepower-per-litre target, future dyno sessions are already being planned. These will involve experimenting with different intake system configurations and timing combinations that showed particular promise during the initial testing.

The second critical aspect of the project is, of course, reliability. This will ultimately need to be validated through extensive hours of service on the racetrack. However, considering the meticulous attention paid to strengthening the bottom end with substantial billet main caps, ARP studs, 360-degree thrust bearings, a robust billet steel crank, and a relatively light rotating assembly, coupled with the reinforced block and the improved lubrication system, along with the lighter valvetrain, superior durability appears to be a logical outcome. Only time, and the upcoming VARA and SVRA races, will tell the full story.

Coventry Climax: Ready for Your Vintage Racer

Enthusiasts of the Coventry Climax marque will be delighted to learn that the team at Penta Motorsports has been actively involved in "rescuing" a number of FWA and FWB pump engines from Europe. These engines are now being prepared and are available to be converted into race-ready powerplants for vintage racers. Penta offers these conversions in a variety of displacements, including the standard 1098cc and 1460cc configurations, as well as custom sizes. Furthermore, Penta Motorsports provides a comprehensive service for refreshing and rebuilding existing Coventry Climax engines, ensuring these iconic powerplants continue to grace the circuits for years to come.

Frequently Asked Questions:

• What was the original purpose of the Coventry Climax engine?
  The Coventry Climax engine was originally designed and manufactured as a portable fire pump engine for the British government.
• What modifications were made to make the FWA engine race-ready?
  Key modifications include billet-steel main caps, 360-degree thrust bearings, a billet steel crankshaft, Nikasil cylinder liners, forged pistons, improved lubrication system with a windage tray and enhanced oil pump, a ported cylinder head with larger valves, and a performance camshaft.
• What kind of power output can be expected from a modified Coventry Climax?
  In the case of Steve Sanett's build, a peak output of 144.8 horsepower was achieved at 7,200 RPM, with the goal of exceeding 100 horsepower per litre.
• Are modified Coventry Climax engines available for purchase?
  Yes, Penta Motorsports offers converted FWA and FWB engines in various displacements and can also refresh existing Coventry Climax engines.
• What racing series are these engines typically used in?
  These engines are primarily used in vintage sports car racing, such as events organised by SVRA (Sportscar Vintage Racing Association) and VARA (Vintage Auto Racing Association).

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