Harry Weslake

Automotive Engineer and Foremost Expert on Engine Tuning

Harry Weslake

Harry Weslake started his working life as an apprentice working on gas meters, tinkering with and improving motorbike engines in his spare time.  He came to the notice of Bentley helping them take the first four places of the 1929 Le Mans 24 hours endurance race.  He worked for William Lyons to improve performance of the Standard engines used by SS Cars and was one of the team of engineers who developed the Jaguar XK Engine.

Harry Weslake was born in Exeter, on 21st August 1897, the second son of Henry John Weslake a director of Willey and Co – a large employer in Exeter making gas meters.  His first home was Clyde House, Princes Street, in the St Thomas area of Exeter, a comfortable, middle class area from which, his father could walk to work.  Harry was sent to Exeter School where he preferred sport to study, and he soon learnt that physical fitness was one way of keeping the school bully at bay.

As a schoolboy, he acquired a bicycle, but craved a motor-cycle.  He designed a system where a motor would drive a third wheel next to the rear wheel on his bicycle, rather like a side-car.  His father was not impressed by the design which was not developed any further.  A couple of years later, the Wall Auto-Wheel was marketed (patented in 1908, on sale from 1909 to 1914), forcing his father to apologise for his lack of faith in Harry’s original concept.

First motorcycle ride

In 1912, at the age of fifteen, using his pocket money, Harry applied for his first driving licence, and immediately hired a Swiss Motosacoche motorcycle from the St Thomas’ Motor Cycle and Cycle Car Garage.  This first motorcycle outing was not a success as the drive belt broke, and he had to return with the motorcycle by train.

His father had Harry apprenticed to Willey and Co with the aim of progressing through all the departments, learning the ways of the tool room, drawing office, foundry and engineering shop.  This was good training for what would become his future career.

At the outbreak of war in 1914, the 17 year old Weslake tried to enlist with the 7th Devons, but his employment with Willeys as an apprentice excluded him. 

In 1915 to help him travel to work his parents agreed that he could have a motorcycle and a Rudge Multi, costing £58 15s (£58.75p), was ordered from the Rudge dealer in Sidwell Street.  Not only did this provide him with transport to work but it started off his interest in racing.  He organised and entered many hill climbs around the Exe Valley and Dartmoor, the Rudge providing an ideal steed.  However, given his penchant for tinkering he decided he could improve the gearing and fitted an NSU two-speed gear to the crankshaft, allowing the gear range to be doubled.  

Wartime and initial work on carburettors

Patent drawings for the
Wex Carburettor

In 1916 (now 18) he joined the Royal Flying Corps (which in 1918 became the Royal Air Force), and was posted to Hastings as a cadet pilot.  The training required attending lectures in the workings of the combustion engine, an area in which he was often ahead of his instructors.  He so impressed one of the instructors that he was taken to see the Chief Instructor, Major McClure, who asked Weslake to design and build two carburettors for testing on aero-engines.  His solution was installed on the test engine and started before all the others, proving its sound design. 

Weslake turned his efforts to improving the Rudge’s performance which had a carburettor known as a Senspray, that injected fuel somewhat like a scent spray.  It was a better arrangement than other carburettors, but open for improvement.  He improved upon the design, leading to better fuel economy and a joint patent taken out with his father in 1918.

Weslake was discharged from the RAF in 1919 to return to civilian life.  By 1921, the family had moved into Franklyn House, Cowick Lane in Exeter and soon after both his mother and father died from cancer.

Wex Carburettors

Harry started his own engineering company to manufacture his carburettor, with the name of Wex (from Weslake and EXeter) Carburettors, based in Fulham Road in London.  One of his initial three employees was Stan Glanfield who in 1927 rode around the world on a Rudge motorcycle and side-car.  While in Brisbane, Stan saw motorcycles race on cinder tracks, and returned to England with a team of Australian riders to stage the first Speedway meet in England, in Epping Forest during February 1928.  Glanfield’s brother Leonard, was one of the founders of speedway and started the Exeter Falcons team.

Harry Weslake (standing)
and Gordon Cobbold testing a Sunbeam motorcycle

The Wex was certainly one of the best performing carbs available requiring only a single lever to operate, and gave significantly better fuel economy with a cleaner gas flow, which boosted power.  Soon the Wex could be seen on all sorts of competition machinery, including Sunbeams, Brough Superiors, and Zeniths.  George Brough insisted that Weslake personally road test Brough SS100s fitted with the Wex carb, to see for himself how the machines performed.

Gordon Cobbold, a young racing motorcyclist, who competed at Brooklands, fitted a Wex carburettor to his Sunbeam motorcycle, and had some success.  He persuaded Weslake to sponsor him so he could retain his amateur status and Sunbeam became interested and agreed a joint sponsorship deal.  

John Marston, owner of the Sunbeam factory, contracted with Weslake to tune their competition engines.  In 1923 Weslake was given three 500 cc OHV Sunbeam engines to tune, and while externally identical, he found their power output varied by almost 20%.  He set about investigating what must be a logical reason for these differences. 

Weslake’s original airflow test box

Here his time working in the family business came to the fore; remembering the testing facilities at Willey & Co which measured the volume of gas metered by coin-slot pay devices.  Weslake reckoned that it would be very useful to measure the volume of fuel-air mix which passed through the cylinder heads, to see if there was any correlation between the volume of gas passed and their power output.  Weslake developed a method of measuring the air flow through a carburettor, based on a system developed by Steven Simpson, who designed the penny in the slot gas meter for Willeys.  Weslake quickly found a positive correlation between the ‘good’ and ‘bad’ Sunbeam cylinder heads, and how efficiently they moved a given volume of gas.  His hastily set-up test rig soon saw considerable action testing other cylinder heads and remained in continuous usage right into WW2. 

The Sunbeams he tuned using his gas-flow tests were shortly gaining plenty of Brooklands ‘Gold Stars’, for laps at over 100 mph during a race, and winning TTs and GPs across Europe. 

Weslake experimented endlessly with shaping inlet and exhaust ports, and within a short time was the foremost expert on cylinder head tuning in the world. 

However, all was not well with the motorcycle business and after Wex were not paid for a large consignment of carburettors, they ceased trading in 1926 due to cash flow problems.

Weslake as Consultant

Weslake was taken on by Automotive Engineering on a retainer of £500 per annum, and W O Bentley asked to meet him.  Bentley had been developing an engine that was giving very poor output, and Weslake was asked for his ideas on how to improve it.  Airflow tests were made and he increased the power of the engine by 20% to 40%.  Bentley then took Weslake on, on a retainer, to continue development of the engines.  In 1929 Bentleys, with Weslake-tuned engines, gained the first four places at the Le Mans 24 hours race, and the first two places in 1930. 

With effective gas flow test methods and a good sense of what worked and what didn’t, Weslake brought power improvements to many engine designs in the 1920s and 30s developing engines for Austin, and MG, among others, before being asked by William Lyons to improve the engines on their SS Cars.

Work on Standard  Engines for SS Cars

When SS Cars started making and selling their own complete cars, rather just building Swallow bodies for Austin Sevens, Wolseley Hornets etc, they turned to the Standard Motor Company to provide the basic engineering.  Standard made a series of bespoke chassis equipped with Standard suspension and brakes and Standard engines.  The SS range consisted of 3 basic models: 1½ litre, 2 litre and 2½ litre all with side-valve engines (which were then the industry norm).  None of these engines were particularly powerful and the cars were criticised for being ‘all looks and no go’. 

William Lyons had had experience of overhead valve engines in the Wolseley Hornet Swallow and knew the engines could be improved upon. 

The Standard 20 hp 6-cylinder side-valve engine delivered a maximum power of 65 bhp at 3,800 rpm.  In 1933 the side-valve engines were given aluminium cylinder heads (approved by Standard) to improve the situation, allowing the head to conduct away more heat and allow more power.  Unfortunately, under arduous conditions, in the 1933 Alpine Trial, the different rates of expansion between cast iron block and the aluminium head caused the heads to distort and gaskets to blow. 

Knowing that for his next generation of cars he would need at least 90 bhp to achieve the levels of performance that he was seeking, he looked for a man to solve the problem.  Both William Lyons and William Walmsley had owned Brough Superiors and Lyons had been tinkering with motorbikes since his school days, repairing them for older brothers of his schoolmates.  By age 20 he had owned, repaired and sold over 20 motorbikes.  It is likely that he knew of Weslake and the Wex Carburettor from this time but it was the company that cast the cylinder heads for the Standard engines, Coventry Motor Cylinder Company, that introduced him to Weslake.  It was fortunate that Weslake had recently fallen out with Cecil Kimber of the MG Company and was only too happy to aid MG’s competitor.

At their first meeting, referring to Lyons’ side-valve cars, Weslake who was renowned for his brusque, no nonsense approach to both his work and people is reputed to have said “Your car reminds me of an overdressed lady with no brains – there’s nothing under the bonnet!”  After a ‘first class row’ they adjourned to the pub and came to understand each other better.  Lyons explained that they needed 90 hp for their next model and a contract was agreed on the basis that Weslake should produce a design that exceeded 95 bhp. 

Weslake signed a contract with SS Cars Ltd as a consultant, again on a retainer, and his initial work was to bore the engines out from 2.5 to 2.7 litres but there was very little increase in power taking it to only 70 bhp.  One other attempt to increase power was to add a crankshaft-driven Zoller supercharger to the engine but while it increased the power output, the engine seized up and the supercharging idea was dropped (at least for many years).  Based on years of experience tuning motorcycles with overhead valves, Weslake came to the conclusion that the solution would be overhead valves, which he was sure he could fit to the existing engine blocks, with the valves operated by pushrods off the original camshaft. 

William Heynes joined the company as chief engineer in April 1935, initially concentrating on improving the SS chassis, but also working with Weslake.  By May 1935 the new cylinder head was working on a test bed and producing 102 bhp at 4,600 rpm.  The compression ratio was only 7:1 due to the relatively poor quality petrol available, leaving scope for further improvement.  Unusually for its day the engine was crossflow with twin SU carburettors on one side of the engine and the exhaust manifold on the other.

Weslake had exceeded his contracted target of 95 bhp much to the pleasure of all concerned.

Towards the end of the 1930s Standard produced a 3½ litre engine and SS Cars planned to offer this as an option in their SS100 Sports Cars as well as their saloons.  Weslake produced an over-head valve head for this engine and power output was increased to 125 bhp at 4,250 rpm, again fed by twin SU carburettors.

Wartime and Development of the Jaguar XK Engine

During the war Weslake developed engines for Scammel to be used in trucks and fire pumps, and helped solve problems in Rolls-Royce Merlin engines that powered aircraft and tanks.  

He continued his association with SS Cars (in 1945 to become Jaguar Cars), working on the XK120 sports car and their successors, as well as the Austin Healey – turning the Healey 100 into the 100S. 

Jaguar XK Engine

Underside of XK cylinder head showing hemispherical combustion chambers

The story of the Jaguar engineers working on a new engine design while ‘fire watching’ during the war has entered legend.   The four members of the Jaguar team are generally cited as William Heynes, Walter Hassan, Claude Baily and William Lyons.   Weslake was still working for the company on contract and he had a lot of influence in the design of the original XK cylinder head and was instigator of the original curved inlet port to promote swirl.

The original story was that the design work was done during the war but the testing was done post-war.  The engine went through a number of iterations designated XF, XG, XH and XJ and the first versions, running as early as 1943, were evolutions of the Standard block with overhead valves operated by push rods.  An aluminium cylinder head was produced with hemispherical combustion chambers with almost vertical inlet valves, but this combination proved too noisy and didn’t produce any more power. 

By November 1944 the design had been changed to overhead cams, still with hemispherical combustion chambers with Weslake working on the ports and the valves to improve gas flow.  These changes liberated more power, but still not the level required by William Lyons.  The early engines used downdraught SU carburettors which by October had been replaced with side draught SUs – 13/8 inch on the XK No 1, four-cylinder engine.  The four-cylinder engine never ran as smoothly as required and the decision was made to concentrate development on the six-cylinder version.  It was Weslake’s gas flow testing that proved the valves being set in the head at 35˚ produced the best engine breathing. 

1948 Jaguar XK120 Engine

A six cylinder XK engine was run for the first time on 15 September 1947 recording a power output of 142 bhp at 5,000 rpm.  It was apparent that the six-cylinder layout was a much better and much smoother configuration than the four-cylinder, on which all work stopped. 

XK120 Launch at the
1948 Earls Court Motor Show

The configuration that went into production had a stroke of 106 mm to give a swept volume of 3,442 cc and power increased to 160 bhp at 5,000 rpm.  Jaguar now had a smooth-running, six-cylinder, double overhead camshaft (DOHC) engine and this was put into production. 

The planned Mark VII saloon would not be ready in time for the October 1948 Motor Show due to delays in the development of the monocoque body, so in a period of only 3 months the company designed the XK120 Super Sports Car to launch the new engine.

Weslake continued working on the XK engines during the 1950s, again concentrating on gas flow, valves and ports, developing what became known as the ‘35/40 wide-angle’ head with inlet valves set at 35˚ and exhaust valves at 40˚. Wide -angle head, engined D-types took first and third places in the 1955 Le Mans 24  hour race.

Weslake and Company

After the war, Weslake had a research facility built on land at Rye, in Sussex and named his new venture Weslake and Co, Ltd.  Over the years the company  worked for a number of the motor manufacturers including Austin, Austin-Healey, Connaught, Coventry-Climax, Daimler, HWM, Jaguar, MG, Vanwall and Wolseley.  He also contributed to the development of turbo-charged diesel engines for powerboat racing and was responsible for a V12 Grand Prix engine

Austin ‘A’ Series Engine

He designed the cylinder head for the overhead valve version of the Austin ‘A’ series engine, launched in 1951, that was used in the Morris 1000 and the Mini and received royalties of 5 shillings (25 pence) on each of these engines manufactured.

Norton Manx Engine

in the late 1940s Joe Craig, Team Manager at Norton International hired Weslake to help improve gas flow characteristics in the Norton Manx engine, which included reshaping the inlet and exhaust ports, and improving the turbulence of the fuel/air mix into the combustion chamber. 

Other Racing Engines

Tony Vandervell had known Weslake since the 1930s, as Vandervell had been one of the Brooklands ‘boys’, racing (of course) a Norton at the track with good results.  Thus, when he formed the Vanwall F1 team in the early 1950s he hired Weslake to modify their Ferrari cylinder heads.  

Dan Gurney became interested in Weslake’s racing engine development work, leading to the 1967 V12 Gurney-Weslake GP engine that powered the Anglo American Racers, Eagle GP car.  On 12th March 1967, two Eagle T1G’s driven by Gurney and Ritchie Ginther won the Race of Champions at Brands Hatch.  The same engines powered the Ford GT40 that won at Le Mans Twice, first in 1968 and again in 1969.

It is probable that Weslake, who had contributed so much to head and port design for Jaguar and Coventry Climax, amongst others, was the first to produce what has now become the norm in racing engines- the narrow angle 4-valve per cylinder configuration – combining good flow, generating horizontal swirl within a compact combustion chamber, and fired from a central spark plug. 

Keith Duckworth (the Worth half of Cosworth) states that he arrived at the layout quite independently, in 1967, in the process of creating the outstanding Cosworth DFV (Double Four Valve) racing V8.  No doubt that is true, but Weslake was running a twin cylinder four-valve research engine with 32˚ (same as the DFV) between the valves in 1965, from which evolved the Eagle Weslake V12 GP engine, which made its track debut about 6 months before the DFV.

Weslake Ford Capris

In 1969 Weslake founded a company was to specialise in working on Ford Capris and became the recognised specialist for the preparation and replication of performance Capris.  In its early days, Weslake worked closely with Ford in Cologne to help achieve the car’s now legendary Motorsport success.  Weslake manufactured the Cologne RS2600 engine that Ford fitted to the Capri.  This included the special Weslake aluminium heads used for Ford’s touring car challenge.  The Weslake Ford Capri went on to win its class at Le Mans in 1972 and won all but one round of the European Touring car championship outright in the same year. 

Return to Motorcycles

In 1974 Weslake and Company turned its attention to developing a British speedway engine to compete against the Czechoslovak Jawa engine.  In 1976 Peter Collins won the World Speedway Championship in Katowice, Poland using a Weslake engine, and he was awarded the prestigious RAC Segrave Trophy “For  becoming the first British rider to win the World Speedway Championship.”

In 1977, John Louis, the Ipswich captain won the British Championship, with the engine.  

His Final Race Meeting

On the 2nd September 1978, Harry Weslake attended the World Speedway Championship at Wembley.  Although a Jawa engined rider won the event, the track record was broken by Michael Lee on a Weslake machine.  

After the event, Harry Weslake collapsed at a reception and died of a heart attack at the age of 81.

Postscript (1) – Biography

Weslake’s achievements are far too numerous to list in full here but his biography, Lucky All My Life, by Jeff Clew does a very good job in this respect, if you can get hold of a copy.

There is also a very good Timeline of Weslake and his Company’s work on the Weslake Engineering Company website. 


Lucky all my Life
Biography of Harry Weslake
by Jeff Clew

Postscript (2) – Blue Plaque

In 2016 Mike Dalby, of the Crash Box and Classic Car Club, contacted Exeter Civic Society about installing a blue plaque on Harry Weslake’s first home.  On 20 April 2016 the plaque was installed at Clyde House, 16 Prince’s Street South, St. Thomas, Exeter and unveiled by Mike Dalby.

Weslake’s Blue Plaque


The Blue Plaque inscription reads:


HARRY WESLAKE 1897 – 1978
An inspired engineer
whose revolutionary designs
gave car, motorcycle and
aero engines more power
lived here
1908 – 1919
Crash Box and Classic Car Club, Devon


His name also lives on in Rye, East Sussex as the Weslake and Company site has been re-developed and is now called the Weslake Industrial Park.


Author: Tony Merrygold

©  Jaguar Daimler Heritage Trust


Sources and Further Reading: