Design Within the complicated corporate lineage, the reputation of Coventry Climax as a top-rate engine designer-builder is largely credited to
Walter Hassan and
Harry Mundy, who designed and developed the FW together. The following design aspects are credited to these two people, except the last two items, in which Peter Windsor Smith played a considerable role in place of Mundy, who left the firm in 1955 and returned in 1963. • Designed as a fire engine component, one unique requirement the Feather Weight fulfilled was the ability to be run at nearly full-throttle without a proper warm-up. This required careful attention to lubrication and thermal expansion rates on its parts, which translated into legendary durability in rough racing environments at the price of high oil consumption. • Another technical significance of the FW series, which was carried over to the FWM, is an interpretation of
Harry Ricardo's intake
turbulence theory, whereby intake and exhaust valves are tilted to the same side of the engine where the intake and exhaust ports are located. In the
SOHC reverse-flow cylinder head design, where valves are actuated directly under the camshaft, and where the intake and exhaust ports are located fore and aft of the cylinder bore centre, this arrangement allows intake and exhaust flows to encourage a swirl in the same rotational direction in the combustion chamber going into and coming out of the cylinder. • Later
crossflow DOHC FPF designs incorporated the same concept in a completely different arrangement, where the tracts in the intake manifold are connected to the intake ports in a staggered manner, in a somewhat corkscrew fashion, to create the turbulence by the intake flow. • The FWMV had an unusually small exhaust valve size to intake valve size ratio for an increased intake flow speed for the same reason. At one time, the FWMV's exhaust valve size (1.37") exceeded the inlet valve size (1.35") on the most successful Mk.4 version. • Separately, the FWMV Mk.III and Mk.4 became famous for proving that
flatplane crankshaft design is more advantageous for a racing
V8 than a
crossplane, in spite of the engineering theories at the time suggesting otherwise. Flatplane crankshafts became the norm in V8 racing engine designs from the 1970s on.
F Type At the Olympia Motor Show in 1923, Coventry Climax listed four F-type 4-cylinder water cooled engines. All had 100 mm stroke, and the bores were 59 (1,094 cc displacement), 63 (1,247 cc), 66 (1,368 cc) and 69 mm (1,496 cc). The
GWK car had featured in Coventry Climax adverts from late 1920 with a Coventry Climax 10.8 hp 4-cylinder engine, the same horsepower rating as the 66 mm bore F type. The engines were available either separate or in unit construction with a three speed gearbox.
ET 2 Also displayed at the 1923 Olympia Motor Show was a 1,005 cc twin cylinder 2-stroke engine. The bore was 80 mm and the stroke 85 mm.
OC 10 hp At first, the OC was made with a capacity of 1,122 cc as a
straight-four using a bore of 63 mm and stroke of 90 mm with overhead inlet and side exhaust valves, producing . It was introduced in the early 1930s and also built under licence by
Triumph.
MC The OC engine had morphed into the MC engine by 1933. It looked virtually identical, but there were internal differences. It was still 1,122 cc, I.O.E., and four cylinders inline, but the camshaft was different, as were the cam followers. The timing marks on the flywheel are now observed from the top of the engine rather than the underside as on the OC. Carburation varied, from the side draught
Solex, the down draught
SU, to the progressive choke down draught and then a larger side draught SU system on Triumph engines. The engine was water-cooled by
thermosyphon with no water pump or fan.
JM A six-cylinder version of the MC engine, the JM, was made with a capacity of 1,476 cc with a 59 mm bore, developing . The JMC version had its capacity increased to 1,683 cc by increasing the bore to 63 mm and produced . It was different from the 4 cylinder engine in that it had both a water pump and an oil filter, whereas the 4 cylinder engine relied on thermosyphon alone and no oil filter.
FW The FW 38 hp 1,020 cc straight-four SOHC was designed by Hassan and Mundy as the motive unit for a portable service fire pump which was supplied to the government under three contracts totaling over 150,000 units. This engine was revolutionary in its lightness, with a bare weight of 180 pounds, combined with the maintenance-free valve adjustment using shims under an overhead camshaft. In 1953 it was adapted for automotive racing as the 1,098 cc FWA retaining the cast crank three main bearing construction of the FW but with a distributor ignition in place of a magneto, a different camshaft, and a higher, 9.8:1 compression ratio. With a bore of 2.85 inches and a stroke of 2.625 inches, it produced at 6,000 rpm and was first used at Le Mans in 1954 by
Kieft Cars. After the FWA was introduced, the FW was renamed to FWP (Pump). The larger bore (3 inches) and longer stroke (3.15 inches) 1,460 cc FWB engine followed; it retained the FWA head but had a forged steel crank and produced a nominal . In 1966–67,
Fisher-Pierce of America imported an 85 hp version of the FWB with twin-carburetors to be mounted vertically in their outboard marine unit. This
outboard boat engine came out to the market as Bearcat 85. for which the FWE (E for Elite) was developed The most significant of the series was the FWE which used the FWB bore size and the FWA stroke for a displacement of 1,216 cc. In exchange for a 1,000 unit purchase agreement signed by
Chapman, it was specifically designed for the
Lotus Elite with forged steel crank but became a favourite with a number of sports car racing firms for its racing durability and high power-to-weight ratio. • FWE Stage I – 10:1 compression ratio, single 1-1/2" SU H4 carburetor on cast iron intake and exhaust manifold, 75 bhp at 6100rpm • FWE Stage II – Dual 1-1/2" SU H4 carburetors on alloy manifold, standard on Series 2 Elite, 80 bhp at 6100rpm • FWE Stage III (Super 95) – 10.5:1 compression ratio, dual twin-choke Weber 40DCOE, 95 bhp at 7000rpm • FWE Super 100 – Five-bearing high lift camshaft, steel timing gear, ported head, 100 bhp • FWE Super 105 – 11:1 compression ratio, racing (tuned steel tubular, rather than cast) exhaust manifold, 105 bhp The FWE powered Lotus Elites won their class six times and the
Index of Thermal Efficiency once during the
24 Hours of Le Mans. The FW series engines in modified forms also powered
Lotus Eleven cars which took three class wins at Le Mans and one Index of Performance win. Other FW variants included a short-stroke (1.78 inches) steel crank version of the FWA named the 744 cc FWC, as used by
Dan Gurney early in his career in US club racing. The objective of this engine was for Lotus to campaign for the 750 cc Le Mans
Index of Performance prize in 1957, three engines were made for this purpose, and it won the prize in a
Lotus Eleven driven by
Cliff Allison and Keith Hall. Lotus also campaigned the FWC at Le Mans in 1958. Another variant was the 998 cc FWG, which was designed to the 1,000 cc
FIA Formula Two rules, also with a steel crankshaft to produce just shy of 100 bhp at 9,000 rpm. There were reports to the effect that the engine was not run because of fears about the rumoured power of other 2.5L GP engines, but shortly after,
John Cooper brought a race-winning, works Maserati F1 engine he had on loan into Coventry Climax, where it produced 225 bhp running on the same dynamometer upon which the FPE had made 264 bhp after some development. Ultimately, development on the engine was abandoned in favour of focusing on the FPF engine, which was already proven competitive in 1.5L form with side-draft Weber carburetors in the F2 races, and the entire stock of parts was sold to Andrew Getley in the mid-1960s. When the Formula One regulation changed to 3 Litres for 1966, Mr. Getley permitted
Paul Emery to rebuild one FPE to 3 Litre format and fit it into a one-off Shannon steel monocoque chassis to make the
Shannon F1 car named
SH1 driven by
Trevor Taylor at
1966 British Grand Prix. Bored out to 3 Litres and Tecalemit Jackson fuel injection installed, this Emery-built FPE produced 312 bhp on the dynamometer at
Chrysler's
Kew facility. Remnants of other FPE parts were much later found by the then-owner of 1954 Kieft F1 chassis, Gordon and Martyn Chapman, in an air-raid cellar in the abandoned building which used to belong to Bill Lacey (of Power Engines Ltd., a Coventry Climax specialist) near the main entrance of
Silverstone Circuit, including 3 blocks, 2 cranks, 16 cylinder heads, 20-some cam covers (carriers?), two card boxes full of timing gears and camshafts, which all belonged to "Doc Murfield" who had purchased the parts from Andrew Getley in 1968-69 and had entrusted them to Bill Lacey. These parts were assembled into two engines under the ownership of Gordon Chapman and then under Bill Morris, who bought the engine parts and the Kieft chassis after Gordon Chapman's death. One engine was sold by Chapman to the then-owner of Shannon SH1, and this FPE is said to be in Austria together with Shannon SH1. Another using two of the later type twin spark plug heads in the stock, was run in the original 1954
Kieft-Climax V8 Grand Prix chassis with downdraft Weber 40IDF carburetors when they were finally mated, and the construction finished on 21 September 2002 at
VSCC Silverstone Meeting, and this car was campaigned in
VSCC events for the next 10 years. Four sets of period-correct Weber 40DCNL carburetors were installed on the FPE during the 10 years, and the car, one spare chassis, and the FPE parts were sold in a lot at
Bonhams Chichester auction on 15 September 2012 for £185,000.
FPF T54, the first rear-engine Indy car, with 2.75L FPF The FPF was a double overhead cam all-aluminium
four-cylinder that was essentially half of the above
FPE V8 engine, which was designed as a pure racing engine from the outset. Designed in 1955 and becoming available in 1956, it had gear-driven camshafts, steel alloy cylinder sleeves, and individual oil scavenge as well as pressure feed pumps for a dry sump system. Carburetion was by two twin-choke
Weber DCO side-draft carburettors. It started life as a 1,475 cc
Formula Two engine by enlarging the 2.95 in bore of the FPE to 3.2 in with the slightly increased stroke, and was gradually enlarged for use in
Formula One that allowed 2500cc until 1960. A 1,964 cc (3.4" x 3.3") version took
Stirling Moss and
Maurice Trintignant to
Cooper's first two Grand Prix victories against 2.5 L opposition in 1958. After the interim 2,207 cc (3.5" x 3.5") version, a larger block was cast to result in 2,467 cc (3.7" x 3.5") in 1958, and then to a full-sized 2,497 cc (3.7" x 90 mm) in 1960.
Jack Brabham won the
World Championship of Drivers in both
1959 and
1960 driving FPF powered Coopers. The FPF with the smaller block was then adopted to the new
1.5-litre Formula One of 1961 as 1,499.8 cc (82 mm x 71 mm) FPF Mk.II and won three World Championship Grand Prix races in that year. In addition, capacity was increased on the larger block to 2,751 cc (96 mm x 95 mm) for the
Indianapolis 500 and this variant was also utilised for sports car racing, and
Formula Libre racing. The 2,497 cc FPF gained a new lease of life in 1964 with the introduction of the
Tasman Formula and the
Australian National Formula, both of which had a maximum engine capacity of 2.5 litres. It also served as a 2.8L stopgap in the new 3.0 L Formula One regulation, which went into effect in
Formula One return to power in 1966. The 2.5L Coventry Climax FPF engines used in Australia at the time were in fact manufactured under licence by Australian engineering company
Repco.
Notes: FWM The FW was designed in response to the British Government's
Ministry of Defence (MoD) requisition outline issued in 1950, specifying a water pump and petrol engine combination to deliver 350 gallons of water per minute at 100 psi, with 35 to 40 bhp at the weight of 350 pounds or less. The successful bid by a portable pump driven by the 38 bhp FW mounted in a steel pipe frame resulted in a 5000 unit supply contract in 1952. By 1956, 1,460 cc FWB was adapted back to a higher output fire pump engine as FWBP with good results, and led to the realisation that the newer 35 hp general purpose engine specification by the government (including for Search Lights and Generator Sets) could be met with a smaller displacement engine than the FW(P). This resulted in the development of SOHC 654 cc (2.35" bore x 2.25" stroke) FWM in 1957, which basically was a smaller and lighter version of FWP with many detailed differences that reflect the improvements and cost-cutting as well as weight-saving measures found in the development of FWA, FWB, and FWE. The differences include: • Deletion of the intermediary shaft (Jackshaft) making the cam drive a single stage chain as opposed to FW series' two stage gear/chain set up. This made the camshaft turn in the same direction as the crank. • Conrod big end part line was made horizontal, as opposed to the previous diagonal. • The number of cylinder head studs was reduced from 18 to 10.
Evolution FWM was then developed into an automotive engine as FWMA of 742 cc with larger 2.45" bore and 2.4" stroke in 1959. Several versions of FWMD diesel utility engines, including a marine version, followed, and then a chain-driven DOHC 2 valves per cylinder
crossflow cylinder head was developed and became the FWMC, succeeding FWC as the all-out racing engine for the 750cc class. FWMC became known for the unusually loud and high-pitched exhaust note when installed in a specially made super-light version of
Lotus Elite run by
UDT Laystall at
1961 Le Mans 24 Hours. It was this 4 cylinder DOHC FWMC that was used as the basis to develop the successful
FWMV V8. However, coinciding with the promotion of
Peter Windsor Smith as the Chief Engineer (reporting to Walter Hassan) in 1960, Coventry Climax reverted (as in OC and JM engines) to using the metric system for specifying piston and crankshaft sizes, so FWMV cylinder dimensions were bore and stroke, ending up having almost no parts interchangeability to FWMC despite having an extremely similar piston and cylinder-head design. To streamline production, the 63 mm × 60 mm sizes were later applied back to the 4 cylinder engine to form the 748 cc FWMB with the same cylinder head as the FWMA.
FWMV The 1.5-litre FWMV V8, developed from FWMC using a
crossplane crankshaft, was designed in 1960 and ran for the first time in May 1961. It produced from 11.5:1 compression ratio and made its debut on
Cooper T58 at 1961 German GP in August. Initial developments resulted in at 8500rpm soon after, but
Jack Brabham at Cooper and
Stirling Moss at
Rob Walker Racing Team suffered over-heating problems while enjoying a great amount of power for the rest of the season. The problem was diagnosed to originate in the steel cylinder sleeve's thermal expansion rate being different from the Aluminium alloy cylinder-head, causing the
Cooper Ring in between the sleeve and the head to leak: "[T]he water temperature remained relatively constant, the height of the aluminum cylinder block also remained relatively constant, whereas the cast iron cylinder liner was subject to temperature changes due to firing conditions, that is, throttle open and throttle closed. Once the cause was known, it was quickly and easily rectified by replacing the lower flange on the cylinder liner with an aluminum sleeve, sealing into the base of the cylinder block, and supporting the liner under the upper flange." With this problem solved in the Mk.II 186 bhp version, having a larger 1.35" intake valves (1.30" previously), FWMV started to score GP victories, ending the 1962 season with 3 wins for Lotus, 1 win for Cooper, 5 second places and 4 third places, in addition to 7 pole positions and 6 fastest laps. For 1963, Coventry Climax was able to convince
Lucas to supply the cogged belt-driven fuel injection system originally developed for
BRM with then-unique sliding throttle plates with four round intake bores cut-out. With the larger bore (from 63 mm to 68 mm) and shorter stroke (60 mm to 51.5 mm) compared to Mk.II, notable changes include the increase in conrod length (from 4.2" to 5.1" centre to centre, with a shorter piston crown height) and the switch from
crossplane to
flat-plane crankshaft, which surprisingly did not increase vibration in the higher RPM range because the longer conrod length (and, to a less extent, lighter pistons) counteracted the increase in
secondary vibration inherent in flatplane design. The flat-plane crank was adopted partly due to
Rob Walker's proposed successor to the 4WD
Ferguson P99 Formula 1 having a front engine layout, which could not accommodate exhaust pipes that merge with pipes from exhaust ports on the opposing bank on
crossplane arrangement, but this project did not materialise. Later, such an elaborate crossplane exhaust system became well-known as "
bundle of snakes" on the
Ford GT40, but was a feature of FWMV Mk.I and Mk.II. This Mk.III developed at 9,500 rpm, propelling
Jim Clark,
Lotus 25 and
Team Lotus to 7 wins, 7 pole positions, 6 fastest laps, and the
1963 World Championship title. Mk.4 was developed for 1964 with yet larger bore (72.4 mm) and shorter stroke (45.5 mm) with a larger exhaust valve (from 1.237" to 1.37") and 12:1 compression ratio to result in at 9750rpm. One-off Mk.5 was made with a larger inlet valve (from 1.35" to 1.40") for , which was delivered to Lotus and used by Clark in the
1964 season. Mk.4 and Mk.5 scored five wins (three by Clark for Lotus, two by
Gurney for
Brabham), seven pole positions, and seven fastest laps. A one-off 4 valve Mk.6 had 1.04" intake and 0.935" exhaust valves, new pistons, cylinder sleeves and crankshaft, and had gear driven camshafts as opposed to the previous chain drive. This engine made at 10,300 rpm and went to Lotus during 1965. Another 4 valve one-off, Mk.7, was built with 1.107" intake and 1.043" exhaust and all the new Mk.6 parts for at 10,500 rpm, and was delivered to Brabham. However, these engines started showing reliability problems. Except for these two one-off 4 valve engines with characteristic ribbed cam covers, all the FWMVs used in
1965 season were 2 valve Mk.5 or earlier versions with various levels of upgrade. This was because Coventry Climax had started the FWMW flat-16 project, which was finally announced at the beginning of 1965, and had more than a handful in things needed to be developed or solved, so the 4 valve configuration on FWMV did not get completely developed nor did reach a series production. However, Jim Clark was able to win 6 championship races (3 with Mk.6), 6 pole positions and 6 fastest laps to become the 1965 World Champion. At the end of the 1965 season, the failure of FWMW project left Coventry Climax with no 3 litre successor to FWMV for the next season, so a 2 Litre version of FWMV was assembled using Mk.4 bore (72.40 mm) and Mk.II stroke (60.00 mm) and was used by Lotus in 1966 as a stopgap until 3 litre BRM H-16 engines became available but with little success. However, Jim Clark won the 1967
Tasman Series with this engine in his Lotus 33. Overall, FWMV powered
Cooper,
Lotus and
Brabham Formula One cars won 22 World Championship Grand Prix races.
FWMW By the middle of the 1962 season, Peter Windsor Smith and Walter Hassan were convinced that the only viable route to more power was through higher revs, and the decision was made, partly in light of Harry Mundy's experiences on the 1.5-Litre supercharged
BRM V16, to develop a 1.5-Litre
flat-16 designated the FWMW. Design work started in 1963, and a prototype was running on the bench in late 1964 with two flatplane flat-8 cranks end-to-end, shrunk-fit to a central spur gear at 90 degrees phase shift to each other. Work on this project continued through the later years of the 1.5 Litre formula with Lotus and Brabham the likely recipients. The engine was fairly compact at 30.9" long (only 1" longer than FWMV Mk.4) and 22.6" wide, but there were a number of design problems still to solve before the formula ran out. Not only had the engine shown no power advantage over the V8 despite its much higher rev limit, but it had mechanical problems that would have required either a major rework to solve properly or, at the least, the need for complete engine rebuilds after 3 hours of running. From the outset, the largest problem was
torsional vibration of the crankshaft, which at one time necessitated a ban on using less than 4000 rpm on the bench. The vibration often caused one or other of the cranks to shear itself off the central spur gear, resulting in the engine becoming two aphasic flat-8s, or the parallel
quill shaft (driven at 0.8 times the crank speed, located below crank, and in turn driving the flywheel and ancillaries) overheated and disintegrated. The central power-take-off system using the parallel shaft was intended to reduce torsional vibration of the long crankshaft, but destructive vibration appeared no matter what was changed in firing order, crank counter-weight configuration or crankshaft weight distribution. As a result, Coventry Climax could not derive revenues from the project, and was further forced to develop a 2-Litre version of FWMV so that Lotus, who built one
Lotus 33 chassis specifically for FWMW, and were counting on using FWMW's anticipated 3-litre successor, could avoid missing the first races of the 1966 season. Neither the old four-cylinder FPF nor the eight-cylinder FWMV could be enlarged to 3 litres, and the 11 years old 2.5-Litre FPE parts had been sold off in their entirety and were in the hands of
Paul Emery, who was in the process of enlarging FPE to 3-Litres. Partly because of this project's grand scale failure, and partly because of Jaguar's take over in 1963, Coventry Climax could not develop a 3-litre successor to the FWMW, and announced its withdrawal from the F1 engine business. Its reputation and the long-standing relationship with
Team Lotus were seriously tarnished.
Notes: Jaguar V12 Having designed and developed the successful
Jaguar XK engine under the guidance of
William Heynes at
SS Cars Ltd, Walter Hassan and the team were tasked to develop a Jaguar 5.0 L
DOHC V12 engine when Coventry Climax was purchased by Jaguar in 1963. It was about this time when Walter Hassan convinced Harry Mundy, who had left to become the Technical Editor of
The Autocar magazine in 1955 (while there he also designed the
Lotus-Ford Twin Cam for
Colin Chapman), to rejoin the team, which now included the Jaguar engineer, Claude Bailey, who always worked under William Heynes from the days of XK engine development. William Heynes was the executive in charge of the team, who retired in July 1969. This engine was initially conceived in 1954 for the
Le Mans 24 Hour Race by combining two Jaguar XK cylinder heads on a common 60 degree block. The first prototype was assembled in 1964 with LM8 aluminium alloy sand cast block and flanged cast iron liners, EN4A forged and nitrided 7 main bearing crankshaft for 4994 cc (87 mm × 70 mm). This racing engine, with its intake ports in between the intake and the exhaust camshafts, came out to be the fuel-injected 5L DOHC
Jaguar XJ13 engine in 1966, but more importantly, it was further developed by the same team into the series-production
5.3 L SOHC V12 engine. This engine, with characteristically long intake tracts connecting the four carburetors on the outside of cam covers to the intake ports inside the V angle, came out to the market on
Jaguar E-Type in 1971, on
Jaguar XJ12 in 1972, and, together with the later 6.0 L version, remained in production until 1997.
CFA and CFF After the designing was finished on the 5.3 L V12 and the
Jaguar XJ, Jaguar wanted a modern engine for a smaller version of
XJ. Although Jaguar had gained access to the 2.5 Litre iron block
Daimler V8 with the take over of Daimler in 1960, it was a pushrod engine designed in the 1950s, and was not particularly small or light as it was based on, and had many common components with,
the 4.5 Litre version. In response, Coventry Climax designed an aluminium crossflow chain-driven SOHC cylinder head somewhat similar to the 5.3L V12 head, on FWMV Mk.4 block with a stroked crank and wet sump.
Tecalemit-Jackson fuel injection was used for the development of this 2,496 cc CFA V8 that weighed 300 lb, with a bore and stroke of 80.77 mm and 60.96 mm and the engine was installed on Leonard Pelham Lee's personal
Triumph 2000 Estate. The testing was promising, producing more than 200 bhp at 7,000 rpm in flexible sports-car tune and a 1,812 cc CFF version was prototyped; however, this 1.8 – 2.5 Litre baby XJ project was killed along with the V8 engines when
British Motor Holdings merged with
Leyland Motor Corporation in 1968 for the strategy to eliminate internal competition against what came out to be the
Rover SD1.
F1 engines The F1 engines were as follows (bore and stroke figures are unified in inches on Metric designs for comparison): • 1954 FPE 2492cc V-8 2.95 x 2.78125" @7900rpm Godiva • 1956 FPF 1475cc 4 cyl 3.20 x 2.80" @7300rpm for F2, ran in GP races • 1957 FPF 1964cc 4 cyl 3.40 x 3.30" @6500rpm • 1958 FPF 2207cc 4 cyl 3.50 x 3.50" power figures unknown • 1958 FPF 2467cc 4 cyl 3.70 x 3.50" @6500rpm • 1960 FPF 2497cc 4 cyl 3.70 x 3.54" @6750rpm ==Formula One legacy==