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Coventry Climax

Making a new fire-pump

In 1950 (at the time of the Korean war) the specifications for fire-pumps, that the U.K. Ministry of Defence had set, were changed. Army fire-pumps had to deliver 35bhp at 3,500rpm. plus they had to be very light-weight. September of that year, Leonard Lee of Coventry Climax met his new chief engineer, Walter Hassan (1905-....) and they decided that their product needed an up-date.
Hassan took a close look at motorcycle technology (which at the time was ahead of cars), and in particular at the Sunbeam S7. The S7 engine was entirely of alloy, it had wedge-shaped combustion chambers, and an overhead camshaft.

Seven months later, in April 1951, the first 1020cc FW engine was ready, FW for Feather Weight. When started for the first time, it ran successfully, and easily produced 38bhp. They were rewarded with a Home Office contract.

Racing the engine

As Mr. Lee thought that victories in races would influence prospective buyers, it was decided that the engine would be raced. Already the gentlemen of the racing business were knocking on his door since the engine had been on display at the Earls Court Motor-show, on the marine stand.

It was obvious that the engine was not developed with racing in mind. The awkward size of 1020cc needed modification and other changes had to be made to make the FW into a racing engine.
In 1953 the FWA was delivered to the market, A for Automobile. The block had been rebored, new pistons were fitted, as were a steel crankshaft and twin carbs, alterations to the valves and ports were made and the compression ratio was increased. Power output of the little fire-pump had been increased from 38 to 72bhp at 6100rpm.

The first car to use a Coventry Climax engine in a contest was a Kieft with a 1097cc FWA. The match being the 24 hours of Le Mans in June 1954. The Kieft did not finish as its rear axle broke.


The season of 1954 saw Coventry Climax-powered cars winning races. The company found themselves in a monopoly situation. Competition mostly used much modified Ford and MG units that were expensive and unreliable.
Leonard Lee did not sell any specials to anyone, not even the persuasive Colin Chapman of Lotus. Everyone was given an identical engine. And development marched on. Compression ratio was increased and later on so many changes were made that it was called the Mark II.

The absolute capacity limit for the block was represented by the FWB, of which only a few were made. These engines, that contained nearly 1500cc, were raced in 1956 by Coopers. And it was one of these cars that won the British Grand Prix in July of that year.

When Colin Chapman started thinking up the Elite in 1957, Coventry Climax agreed to provide the engines. But only if they could be garanteed a minimum order of 1000 units. The Feather Weight Elite (FWE) was produced from 1958 to 1963. It had a relatively unstressed output of 72bhp. The Lotus 14 (Elite) was winner of its class at Le Mans on 6 consecutive years from 1959 to 1964.
These engines were also sold to Jack Brabham who fitted them (as after-market extras) to sports cars of the day. And successfully so !

Mr. Chapman then convinced Coventry Climax to develop an ultra-short-stroke version of the FWA. He would like one to use in the 1957 'Index of Performance' class at Le Mans.
This FWC came alive and won with ease. It needed constant high revs, having no usable power below 6000rpm, but this was hardly a disadvantage during the race. Though of course it was unsuitable as a road engine.

It did lead to further modifications in the original FW unit, as it was clear that it didn't need 1020cc to provide 35bhp. Walter Hassan and Harry Mundy developed a new unit of only 653cc, which could do what the old FW did, but was 100lb (45kg) lighter. It was named FWM, M for Marine, as it was intended for marine use. This new engine was able to operate either horizontally or vertically for outboard use. The American market remained as uninterested as they had been in 1951, despite a later increase of capacity to 745cc and intensive development.

For 1958, Colin Chapman persuaded the company to develop an enlarged (745cc) racing derivative of this engine, for his cars to use at Le Mans, when it was dubbed FWMA (Feather Weight Marine Automotive). (That year, and in the future, it was not a lucky engine for Lotus).
It was this FWMA that Mike Parkes had in mind for his Imp.

The fire-pump that wins races
capacity type bore stroke compressionmax. bhp used in carbs
FW1020cc 38bhp fire-pump 
FWA 1098cc 72.4mm 9.8 : 1 75bhp@6800rpm  
mk 2
1098cc 72.4mm 83bhp@6800rpm  
FWB 1480cc 76.2mm 80mm 100bhp Coopers '56 
FWE 1216cc like FWB like FWA 72bhp Lotus Elite
FWC 750cc like FWA 72.4mm 45.2mm 59bhp@8000 Colin Chapman
Le Mans 1957
FWM 745cc fire-pump
FWMA 741cc 4 cil. 64.3mm 57.2mm   chosen by Mike Parkes to be further developed for the Hillman Imp  
FWMC 742cc twin cam       83bhp @ 8200rpm ulta-lightweight Elite in the 1961 Index of Performance / Thermal Efficiency
(half of a new GP engine)
FWMV 1500cc V8 63mm 60mm   174bhp@8600rpm Lotus 25
478kg (1052lb)
approx. 173mph
FPF 2495cc inline 4
8 valve
twin ohc
94mm 90mm 12.1 : 1240bhp@6750rpm Cooper T51
118lb dry
Twin double
choke Weber
38 carbs

Coventry Climax is still in business, but they don't provide parts for long discontinued engines. They licensed other companies:
  • In the UK:
    Climax Engine Services
    Unit 1 Lotus Drive, Willersey Industrial Estate, Willersey, Broadway, Worcestershire, WR12 7QF
    Tel. 0.1386.852725, Fax 0.1386.765143
    old address: 82 Northwick Park Estate, Blockley, Glos.
  • In the US:
    Hutton Motor Eng
    1815 Madison St, PO Box 3333, Clarksville TN 37043-3333
    Tel. (931) 648 3333, Fax: (931) 648 1119 (old phone no. +1 615 648 3333)

Another known address: Mike Brotherhood near Calne, Wiltshire
Tel: 01249 817338 Fax: 01249 760530 Open Mon-Sat 9-9.
Historic Lotus specialist. Restoration, spares and sales.
Complete service for all spaceframe Lotus and Coventry Climax engines.

Mentioning these addresses does not imply recommendations.

Dewar Trophy for Climax

In May of 1964 at the RAC Leonard Lee, chairman and managing director of Coventry Climax was presented with the Dewar Trophy for 1963. The trophy, dating back to 1906, which is awarded on the recommendation of the RAC's technical and engineering committee for the most outstanding British achievement in the automotive field during the year, is not necessarily annually awarded. Last time awarded: 1959 to Alec Issigonis, once a junior engineer with Coventry Climax.
The citation reads: "Awarded to Coventry Climax engines Ltd. for the design, development and production of engines which have brought British cars to the forefront in th field of Grand Prix racing."
They were working on four-valve heads for the vee-8 GP engine, and if they gave more power than the two-valve heads in use at that time (which they weren't at that moment) they would release them.

Autocar, 8 May 1964, p.896  



1958	2 GP victories	Cooper-Climax
1959	5 GP     ,,   	Jack Brabham made champion
1960	6 GP     ,,   	again Jack Brabham champion
1960	2 GP     ,,    	Jim Clark in a Lotus

Results in 1965-66
World Championship 1965
 1. Jim Clark (Lotus-Climax), 54 pts.
 2. Graham Hill (BRM), 40 pts.
 3. Jackie Stewart (BRM), 33 pts.
 4. Dan Gurney (Brabham-Climax), 25 pts.
 5. John Surtees (Ferrari), 17 pts.
 6. Lorenzo Bandini (Ferrari), 13 pts.
 7. Richi Ginther (Honda), 11 pts.
 8. Bruce MacLaren (Cooper-Climax), 10 pts.
    Mike Spence (Lotus-Climax), 10 pts.
 9. Jack Brabham (Brabham-Climax), 9 pts.
10. Dennis Hulme (Brabham-Climax), 5 pts.
11. Jochen Rindt (Cooper-Climax), 4 pts. 

On January 1, 1965, Jim Clark made a clean break in his Lotus-Climax at the start of the South African Grand Prix. He led all the way to notch up his first of six consecutive GP wins. He came in nearly half a minute ahead of the Ferrari V8 driven by John Surtees. Clark never seemed to be pressing his Lotus-Climax 33 at any stage.
The 32-valve, 209hp Coventry Climax V8 engine was also used by Jack Brabham in his Brabham-Climax, as did J. Bonnier, D. Gurney, J. Siffert and R. Anderson. One Bruce McLaren was driving a Cooper-Climax, so were Jochen Rindt and John Love. The other Lotus-Climax V8 was Mike Spence's.

Climax engined Racing cars

Lotus MkVIII - The third engine No. FWA ET515/6155, of 4 experimental FW engines for automotive use, was sold to Dick Steed through Racing Engines Ltd, one of Chapman's companies, for £250 - a great deal in 1954. This was installed in his Lotus MkVIII, first registered in July 1954 and carried the reg no. HUD 139
Lotus Mark 9 (or IX), 1955, FWA, Space frame sports racer
Lotus Eleven (or XI), 1956 - '59?, FWA, Space frame sports racer
Lotus 12, 1958, FPF, 1500cc/2000cc/2200cc
The first Lotus single-seater. First GP points.
It made it's racing debut on the Goodwood Easter Monday meeting of 1957. It was driven by Cliff Allison and it dropped out while being third in the field.
Lotus 16, 1958-59, FPF, 1500cc/2000cc/2200cc
First 'real' F1 Lotus. Motorcycle-type gearbox.
Lotus 18, 1960-61, FPF, 2500/1500
First GP win and pole position.
Lotus 18/21, 1961 FPF, 1500cc; FWMV V8 1500cc
RRC Walker team's car to Stirling Moss.
Lotus 21, 1961 FPF, 1500cc
First GP win for Team Lotus. (Ireland, USA 1961)
Lotus 24, 1962-65, 1500cc Coventry Climax FWMW V8
Lotus 25, 1962-65, FWMV V8, 1500cc; BRM V8 1500cc
First monocoque F1 car. Both championship titles.
Lotus 33, 1964-66, FWMV V8, 1500/2000; BRM V8 2100cc
Modified type 25.

GP gestart
Snelste ronden

FORIX: Formula One Results and Information Xplorer

Climax engined Road cars

Pre-Feather Weight era

Coventry Climax fame did not start with the feather weight fire-pump.

Morgan Aero, Great Britain 1921-1936
The Morgan was the best known three-wheeler, not only in Britain but throughout the world. The three-wheelers occupied an anomalous position in the motoring world, always being exhibited in motorcycle shows and exhibitons.
By 1933 the fiercest Morgan was called the Super Sports Aero. The air-cooled V-twin JAP engine was mounted in front of the bonnet, fully exposed to the elements. A year later this model gave way to a less sporting version with a water-cooled Matchless engine, and in 1934 came the first four-cylinder Morgan, a 1,122 cc Coventry Climax.

Prewar Coventry Climax engines were built by Triumph under licence and used in various Triumphs from 1932-1938, eg. a six cylinder Triumph/Climax ioe in a 1935 Triumph Gloria.

Feather Weight era

Lotus Elite (Type 14)
Production: approx. 1000, 1957-1963
Bodystyle: Two-seater
Engine: Coventry Climax FWE 4-cylinder (1216cc)
Chasis: all-fiberglass

TVR Grantura Mark I
Production: 100, 1958-1960
Bodystyle: Two-seater coup
Engine: Varying, 1216cc Coventry Climax FWE
Engine position: Front
Driven wheels: Rear

Feather Weight engine for an Imp



  1. the original registration document for Dick Steed's Lotus Mk VIII chasssis no. MK6/2 - 4, engine no. FWA ET 515/6155 and first registered in July 1954.

  2. a photograph of Dick Steed in his MkVIII at Castle Coombe, Aug 28 '54, clearly showing the Climax engine
    Lotus the early years / Peter Ross. - Coterie, 2004. - ISBN-13: 978-1902351148. Photograph on page 130.

    another photograph at another circuit with Graham Hill again clearly showing the Climax engine
    Lotus the early years / Peter Ross. - Coterie, 2004. - ISBN-13: 978-1902351148. Photograph on page 142
    The book has an extensive appendix with complete race results and specifications (1951-54)

  3. the British Govt. Home Office Forensic Science Laboratory report on the recovery of the original chassis no after Dave Kelsey had overstamped it when he was forced to re-register the car in March 1955

  4. Coventry Climax Engines Ltd sales record relating to FWA ET515/6155

  5. Walter Hassan's bookClimax in Coventry : my life of fine engines and fast cars / Walter Hassan ; in collaboration with Graham Robson. - Coventry : Mercian, 1975. - 158p, xxxip plates ; 23cm
    ISBN: 0953072126
    Originally published: Croydon : Motor Racing Publications, 1975
    Of special interest to W.O. Bentley, Jaguar XK engine and Climax F1 racing engines enthusiasts.
    Prices :-19.95.

  6. Coventry Climax racing engines : the definitive development history / Des Hammill. - Dorchester : Veloce, 2004. - 190 p.

  7. The Coventry Climax Engine
    Portfolio of Unique Motor book.
    210x290cm. Paperback. 80 pages
    110 franc

  8. The Coventry-Climax racing engine
    Portfolio Unique Motor book
    210x295cm. Paperback. 80 pages
    110 franc

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         Design of the Hillman 875cc engine / Leo Kuzmicki, Craig Miller and Peter Ware
         A feather weight for an Imp

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© Franka

There is a copy in Southwards Museum of New Zealand of a poster by Coventry Climax. It has with a sectioned drawing of the FWA pump unit; it includes detail of the pump-priming scheme, which used manifold vacuum.