production six years ago,
(Criticism is sometimes levelled at British manufacturers on the grounds that they lack initiative
and fail to develop their designs adequately. Consequently, we are glad to be able to show, in
this article, that the old established concern of Jowett Cars Ltd. of Bradford is exempt from this
charge. Their advanced Javelin saloon of 1945 has had its share of “teething-troubles” and it may
not be generally known that much research has gone into curing early shortcomings. Today, in
the words of a Jowett spokesman, the present Series III Javelin and Jupiter engines possess a
tremendously increased reliability factor and incorporate many modifications resulting from
experience in racing which may not be strictly essential under touring conditions. Motor Sport
readers will be particularly gratified to learn that, according to Mr. Grandfield, Jowett’s
Engineering Manager, who generously provided the data on which this article is based, 95 per
cent of the new features incorporated in the Series III Jowett engine are directly related to
Jowett’s participation in racing - ED).
The old established Jowett Company commenced car manufacture as long ago as 1905. Some
time ago, under the auspices of John Baldwin, the present Publicity and London Manager a
fascinating little book was published which outlined the history of this sturdy Yorkshire concern.
Consequently we can dismiss the earlier years after remarking that the firm’s specialty was the
water cooled, horizontally-opposed twin-cylinder light car, for many years of 7 h.p. Rating
afterwards increased to 8 h.p. A very impressive number of these two cylinder Jowetts are still in
service, visual testimony of their good quality and design, which resulted in long wearing
qualities.
Some years before the Second World War it was decided to add a four-cylinder model to the
Jowett range and experimental cars embodied in line engines. It was’ felt inadvisable, however to
break from the long horizontally opposed tradition and when the new car, known as the “Jason”
went into production in 1936 it had a side valve flat four engine. An attempt to offer good
visibility by using a sloping radiator met with a mixed response from the motoring public, but it
can be said that the flat four engine was adopted for sentimental rather than engineering reasons.
It was not until after the war, when an entirely new post-Armistice Jowett was designed that the
horizontally opposed four-cylinder engine was fully exploited. When Gerald Palmer introduced
his brilliant Javelin six seater saloon inspired to some degree by the popularity in England of the
Italian Lancia Aprilia, he retained the flat four engine and achieved comfortable spacious seating
within the wheelbase by reason of the compact dimensions of this engine layout. In addition,
freedom from vibration, a low centre of gravity, and good visibility by reason of the modest
height of the power unit were other flat four, advantages.
The new engine had overhead valves and was first prepared in two forms a 1,200 c.c. Unit of
69.5 by 78 m.m. bore and stroke and a 1,500 c.c. version of 72.5 by 90 m.m. bore and stroke.
The former engine was intended for the home market, the bigger unit for export, both had a
compression ratio of 7.25 to 1.
Subsequently a change of policy caused Palmer to concentrate on the larger engine, of 1.496 c.c.
In its early form this engine had a two bearing crankshaft running in white metal bushes carried
on the crankcase, a circular spigotted cover at one end obviated the need for a split crankcase.
The crankcase was of aluminium alloy to D.T.D. 424 specification, and wet liners sat on a joint
washer at the base and were clamped down by the detachable cylinder heads. The cylinder heads
were of cast iron with a vertical inlet port leading to Siamese valve ports to provide for one down
draught carburettor per pair of cylinders. The exhaust ports were at the bottom of the heads, the
gases being led away by an integral manifold under each head. A metal duct directed cooling
water to each valve seat. The combustion chambers were of stepped type, the inlet platform
providing a ‘squish’ area to promote charge turbulence over the exhaust valves, from which the
mixture was ignited.
The push rod overhead valve mechanism incorporated hydraulic tappet’s to compensate for
dimensional changes in the alloy crankcase. These tappets were lubricated from one of the main
oil galleries, with lubricant filtered by the full flow method.
The new engines, in both sizes, were extensively tested on the bench and on the road, in this
country. The prototypes had 10 m.m. sparking plugs, but subsequently, 14 m.m. plugs were used.
The 1496 c.c. version developed 40 b.h.p. soon increased to 50 b.h.p. by improved aspiration.
During early testing, when, incidentally, a Bradford back axle was used on the prototype Javelin
- later American axle components were tried before the final adoption of Salisbury units
possessing a very high margin of safety - the engines proved mechanically noisy in a harsh
resonating manner. This decided shortcoming in what was destined to be a luxury small family
car was a major problem calling for a cure. Two forms of crankcase had been prepared, one in
cast iron, the other, in aluminium. Experimental work on these early designs made it quite clear
that there was considerable whirl of the crankshaft and a certain amount of flexing of the
crankshaft, as was evident from edge markings on the bearings and deflection tests.
The next development was to prepare a cast iron crankcase and a three bearing crankshaft, the
bearing cap joint faces being horizontal, so that the crankshaft and f1ywheel assembly could be
dropped out of the bottom of the engine. The first experimental engine of this type was of l, 200
c.c. and when experiments were carried out with larger diameter cylinder liners, increasing
capacity to 1500 c.c. considerable crankcase thump was experienced, and to experimentally
overcome this, boilerplate was bolted across the bottom of the bearing caps, overcoming this
problem and pointing out the inherent weakness of this crankcase design. Subsequent
development was the adoption of the light alloy crankcase split vertically permitting the use of
tie bolts, making a very much stiffer job.
Previous experience had determined the fact that the cast iron crankcase did produce a quieter
engine, but it was decided that the alloy crankcase should be proceeded with, it having been
designed for die-casting. The cast iron version was approximately l0 percent quieter than the
alloy one, but was naturally heavier. In view of this and the difficulty at that time of obtaining
iron castings, the split alloy crankcase was decided on. It was at this stage that the 1200 c.c.
project was dropped, as there was such a pronounced performance difference between it and the l
l½ litre engine.
When the revised engine was tested for output, a considerable drop in power was seen to occur
above 4,250 r.p.m. Observation showed inadequate freedom of breathing and poor turbulence in
the stepped head. The valve lift was increased from 0.275 in. to 0.315 in. and the ports cleaned
up. Westlake was called in to inspect the combustion chamber formation and he evolved a semi
pancake head with 14 m.m. plugs, easier to produce and increasing top end power output by 15
per. cent, while providing smoother running. The exhaust system was changed from streamlined
exhaust ports brought out to the bottom face of the head to a manifold bolted to the underside of
the head, the off-side manifold feeding into a pipe running round the front of the engine to enter
the near-side manifold and take benefit thereby of extractor action. The main exhaust pipe led
from the back of the nearside manifold. It had a 1 3/8” inside diameter and the power drop with
silencers was only 3 b.h.p. compared with an open pipe. This new exhaust arrangement, gave a
power increase of l½ per. cent, and no longer were the cylinder heads handed, a production and
service advantage.
Snatchy running below 20 m.p.h. led to an increase of flywheel diameter to the limits of the bell
housing. Another outcome of initial testing was the need to alter main bearing clearances due to
rapid crankcase expansion. A steel housing giving 0.0003 in. to 0.0018 in. clearance at assembly
temperature was finally adopted.
The Javelin now emerged as the first really new British post-war car, a comfortable, brisk 5/6-
seater saloon, giving 75/80 m.p.h. and 28/32 m.p.g. with the advanced aspects of a flat four
engine, torsion bar suspension and wind defeating body form.
The prototype engine, developing 40-45 b.h.p. had been satisfactory in respect of bearings, but
long-distance driving on the Continent with the early production versions showed up a tendency
to run big end and main bearings.
With the aforesaid improved breathing 50-52 b.h.p. was developed at 4,500 r.p.m. and it was
decided that white-metal bearings must be replaced by copper lead bearings, if possible in
conjunction with the existing E.N. 12 steel crankshaft. The flat four engine layout led to higher
oil temperatures than are experienced in in-line designs, which contributed to the bearing
failures.
The first step was to employ sintered copper-lead consisting of 24 per cent lead, 2 per cent tin 74.
percent, copper, with a 0.00125 in white-metal flash in view of the unhardened crankshaft. These
bearings showed no sign of fatigue but were extremely sensitive to dirt and scuffing on the
crankshaft. A hardened crankshaft was consequently adopted and special care was devoted to
assembly and initial running in. It was also found that the stepped location of the big-end led to
distortion on tightening, so a new con-rod was devised the big-end having an offset-serrated face
and clamp bolts increased to 0.375 in. and 400 lb/in, tightening torque. Maximum distortion was
now within 0.00025 in. A dirt-trap hole of 1/16 in diameter had a negligible effect on oil pressure
and consumption. The crankshaft was now induction-hardened on the journals and pins to a
hardness figure of 512-530 Brinell and the bearing surfaces lapped to a finish of 8-12 microinches
against the former 12-24 micro-inches. A softer bearing material of 30 per cent, lead 1.2
percent tin and 68.8 per cent Copper, with a 0.00025 in. plated white-metal layer for running in
was used with the new rods and crankshaft and the bearings now stood up to 50 b.h.p. and 4,750
r.p.m. in spite of the higher oil temperatures and compact bearings of the flat-four layout.
The lubrication system was thoroughly tested in the initial stages of development, an engine
being rigged for measurement of oil spillage from bearings, relief valve, ancillary services, etc.
As a result the feed to the main bearings was increased and the size of the oil ways increased to
7/16” dia. to obviate a possible danger of bearing starvation under cold-start conditions with the
full-flow filter system adopted to ensure clean oil for the hydraulic tappets. The relief valve
exhausted below sump oil level to avoid aeration and later the discharge was by-passed to the
pump suction side within the cover.
When the three-bearing crankcase was used, difficulty was experienced with oil swirl caused by
air transferring from one side of the case to the other. To stop this, a surface baffle was
introduced, much experimentation being necessary to position it so that it was above oil level yet
allowed free passage of air only. Originally the oil pump has been carried on a bearing cap but
the vertically split crankcase obviated this location, so it was moved to the timing case wall and
driven by spiral gears from the crankshaft. The ignition distributor, which was originally
disposed horizontally and driven directly off the camshaft, was now positioned nearly vertically,
with a common drive shaft to the oil-pump, driven from spiral-bevel gears from the crankshaft.
The increase of oil pump capacity represented an increase of oil pressure from 50 lb/sq.in. to 65
lb/sq.in. After its use on competition cars, an oil cooler, built by specialists to Jowett
specifications, was incorporated on production engines in 1952. At first this was placed
rearwards for accessibility of engine, but later was, moved to a location between fan and radiator.
With the oil-cooler in circuit, pressure pulsations occurred at audible frequencies until the
aforementioned dirt-trap-holes in the big end caps were deleted.
(** Direct quote factually incorrect)
Some interesting experiments were made in respect of airflow away from the behind-engine
radiator. Louvres in the bonnet top were found to become ineffective above 50 m.p.h. so pressure
areas were checked and it was found possible to extract air from behind the radiator via apertures
in the front wheel arches, ugly louvres thus being obviated.
Another difficulty experienced with early production engines concerned noisy valve gear, in
spite of the incorporation of Zero Lash hydraulic tappets. Better manufacturing standards were
immediately adopted, but a fairly heavy patter persisted. A special rig was built to investigate
suspected deflection of the valve gear, which was substantiated. The attempted cure was to
change from the somewhat “Fierce” cam form of 0.002” opening ramp and 0.006” closing ramp
to a cam form providing an 0.003” opening ramp of constant velocity and an 0.012” closing
ramp with a combination or variable acceleration and constant velocity, the cam period being
slightly reduced to avoid increased valve overlap. When operation showed no improvement, a
cam with a 0 .006” opening ramp with constant acceleration and a closing ramp of .0.015” with
variable acceleration gave slightly quieter running. By connecting the noise-meter to an
oscilloscope and watching recordings of the valve movement on a cathode ray tube it was
discovered the noise occurred at both opening and closing.
The next step was to design a cam form with an opening ramp of 0.004” and a closing ramp of
0.020” modified to give correct lift. Noise was now considerably less on the closing side but it
was deduced that an opening ramp in excess of 0.006” would be required. A mathematical
investigation was made to ascertain the theoretical seating of the valve for various valve gear
deflections. The final cam gave a 0.008” opening ramp and 0.020” closing ramp. This with
stiffer rockers and rocker mountings, maximum possible cleanliness of oil supply, freedom from
oil aeration, good manufacturing standards of mating parts and stiffer push rods, effected the
desired improvement.
Unfortunately hydraulic tappets became unobtainable during 1950 and the noise level rose
somewhat with the enforced use of ordinary tappets.
Experiments at this stage were made in respect of camshaft and tappet materials. A high duty 1%
chromium cast iron camshaft with a tip hardness of 40-45 Rockwell C. and chilled iron tappets
of similar hardness and a finish of 7-10 micro. inches, gave excellent results up to a cam loading
of 120,000 lbs. per sq. in. A phosphate process on cam and tappet faces to retain oil during
running were found beneficial, but not really necessary but trouble intervened if the tappet head
finish fell below 20 micro. inches and the chill lower than 36 Rockwell C.
Five different forms of liner/piston combination were used in the course of development. Vacrit
high duty manganese chromium iron liners with a 270-280 Brunell surface hardness were
originally used in conjunction with split skirt pistons in LO-EX or LM.13 alloys with 2 D/26
radial thickness pressure rings and a slotted oil control ring.
The liners were first located by a setscrew through the block into the liner skirt, but slight piston
scuff resulted from the retention of dirt particles and the liner skirt tended to distort. Oil consumption
varied from 1,000-7,000 m.p.g. on production cars. Lapped side rings and barrel
ground pistons were tried and assembly and service techniques were developed to obviate oil
leak throughout the engine.
A taper-faced Vacrom chromium plated top piston ring was adopted to cut oil consumption
without entire success. Liner distortion, was suspected and investigations showed that while
0.008-0.0l0” gasket nip at 38/40 lbs/ft. cylinder head tightening torque was satisfactory to retain
gas and water seals this was highly critical, any degree of higher torque loading or excessive nip
caused local liner collapse and consequent distortion. To counteract this the liner section was
stiffened and an internally stepped second ring fitted to facilitate quick bedding in of the
chromium-plated piston ring. After this a Javelin ran 80.000 miles in the course of testing, by the
Avon India Rubber Co. Ltd. gave an average 3,700 m.p.g. of oil at 37-39 m.p.h. average speed
and maximum bore wear averaged 0.002” equal to 40,000 miles per thou.
Carburation was the subject of special attention in view of the Javelin unusual firing order of l,
3,2,4.
Cylinders 1 and 3 fed from one carburettor. To combat weak mixture in the front cylindersThis is incorrect it is 1,4,2,3
of each bank caused by inlet tract surge a 0.550” diameter balancer pipe was introduced between
the two carburettors. Difficulty of working in the conventional exhaust hot-spot resulted in flat
spots between idling and main jets, but adjustment of the level of the Progression hole to the
edge of the throttle blade in the Zenith carburettor cured this. A further induction system
peculiarity was a very harsh staccato noise at the intakes, unacceptable in what was not a sports
engine. Experiments proceeded with many makes of air cleaners and silencer but it became
evident that a very large silencer would be required to attain a reasonable noise level and this
would about cover the engine and render it inaccessible. Consequently Jowett evolved their own
baffle box, accommodated in the alligator bonnet, tuned to length to suit the induction system,
and connected to a resonance chamber, which was coupled to the air intakes by vertical pipes
having squash rubber connections, which broke as the bonnet, was lifted. A non-spill oil bath air
filter was incorporated. Reverting to the carburettor balance pipe, when this was fitted it was
adapted to ventilate the engine in conjunction with an A.C. vacuum valve in the oil filler tube.
A minor development feature was a change from flat pressings to tubular stays as supporting legs
for the cooling fan shaft, as the flat section caused noise as air flowed over them.
To early bearing failures and excessive oil consumption of some Javelins has been added gasket
blowing, but it should be remarked that this was due to too small an asbestos content at the fold
of the gasket and it was only with increased output for competition purposes that contributory
causes came in.
So far we have dealt with the production engine only, and the painstaking research and
development devoted to perfecting this advanced design of flat-four power unit with rear placed
radiator is truly a credit to the Jowett Company - even if the public are well advised in respect of
all new models, to wait until the initial snags have been eradicated before purchasing.
In 1949 the Javelin engine was developed for competition motoring and class victories were
obtained in events as diverse as the Rheineck-Walzenhausen Hill Climb and the Spa 24 Hour
Race. The Spa Javelin saloon gave about 57 b.h.p. and had the oil cooler and copper lead
bearings etc. Flywheel weight was halved, being reduced from 28 lb. to 14 lb. These Javelins
also ran at Silverstone.
Meanwhile, the Jowett Company had decided to put into production the two-seater sports Jupiter
the chassis of which was based on a tubular frame design evolved by Leslie Johnson in
association with the German engineer Eberan van Eberhorst.
The Javelin engine was required to be developed to give 60 b.h.p. at 4,750 r.p.m. for use in the
new car. The compression ratio was raised from 7.25 to 1, to 8 to 1 by reducing the volume of
the combustion space by a change in shape of the piston crown. Javelin port sizes, bearings and
camshaft’ were used unaltered, but heads and ports were polished. A Delaney Galloy oil cooler
was installed, located behind the fan, a Bowman block cooler was mounted on the front of the
offside cylinder block later. Instead of 23 m.m. carburettors, 26 m.m. Zenith 30 V.1.G.
carburettors were used, later replaced by the easier to tune Zenith 30 VM. The oil sump capacity
was retained at nine pints. As there was more room under the car, the off side exhaust pipe joined
the main pipe in rear of the near side manifold and not at the manifold as on the Javelin. The
shape of the Jupiter body called for air extractor louvres, not used on the Javelin, and when
overheating was experienced in Continental driving and Alpine work the radiator size was
increased after louvres had been added in the bonnet top. As noise was now of less moment no
air silencers were used for the carburettors and eventually the Vokes air filters were discarded,
A.C. filters are now used. The fan shaft was mounted in a rubber ring to offer some freedom of
movement and the base of the supporting legs modified to obviate breakage and release of the
fan from its axle. (Alas in the recent Monte Carlo Rally the fan of Becquart’s Jupiter broke away
and punctured the radiator during the regularity test).
It is significant that about this time the Jowett Company issued its “Competition Tuning Notes”
to those Javelin owners who sought an increase in performance. The usual port polishing and
relieving was covered in respect of this particular engine, stronger outer valve springs were
recommended and special pistons we’re declared available for increasing the compression ratio
from 7.2 to 1, to 7.6 and 8.0 to 1, a reduction in combustion chamber space of 2 c.c. and a further
3 c.c. respectively. The standard Zenith VM 4 or 5 carburettors could be replaced by 30 VM
Zeniths and it was assumed that the hardened crankshaft, copper lead bearings, larger water and
oil pumps, later oil filter assembly and the oil cooler would be employed.
Subsequently similar “hotting up” of the Jupiter was permitted, with increase of compression
ratio from 8.0 to 1 up to 8.5 to 1 for 80 octane fuels, this being obtained by using thin gaskets.
Stronger inner valve springs were recommended and the flywheel could be lightened. It was
assumed that correct fitting and assembly would be ensured and that the modified high tensile
cylinder head studs, Lucas DVX4A distributor and the later cooling arrangements used and
Champion L 11S or LA 11 sparking plugs fitted
Charles Grandfield and Horace Grimley who later developed the Jupiter for racing, had tested a
prototype sports version over 3000 miles from John 0’Groats and across France, at a running
average speed of 54 m.p.h. and an overall average of 46 m.p.h. fuel consumption working out at
31 m.p.g.
The next step was to prepare the Jupiter for participation in racing. For Le Mans in 1950 a
compression ratio of 8.5 to 1 was obtained by the employment of thin head gaskets and with
stronger inner valve springs, high duty ignition distributor and lightened flywheel, the output was
64 b.h.p. To obviate gasket trouble the strength of the cylinder head studs was increased from 45
to 60-65 tons tensile, but the number and position of the studs were unchanged. The plugs were
stepped up from Champion L 11S to Champion LA 11. The l litre class was won at 75.84 m.p.h.
For 1951 the porting, valve timing etc., were improved, and after experiments with compression
ratios of 8 to 1, 8.5 to l, 9 to I and 9.25 to 1, the last named ratio was employed. Just over 100
m.p.h. was obtained from the Rl Jupiter, but after six hours at Le Mans the C.A. gaskets
collapsed. A composite copper, asbestos and steel gasket was found satisfactory, after
experiments with solid copper, laminated aluminium, and corrugated cupro nickel gaskets etc.
This gasket is now used on all production engines but eventually, for racing, a gas filled metallic
sealing ring at 600 lb/sq.in. pressure in a circumferential recess on the liner top flange stood up
to the highest compression ratios. A Plexseal gasket was used as a water joint. The gasket
failures were finally traced to sinking of the cylinder liners and this was cured by redesign of the
liner bottom seal, a rubber ring trapped between the liner bottom flange and the crankcase
permitting a metal-to-metal contact between liner and crankcase, obviating liner sinking and
enabling the initial liner interference on the gasket to be maintained. The 1½ litre class was won
at Le Mans.
For last year’s Le Mans Rl’s retained the 9.25 to 1 compression ratio with flat top pistons. The
serrated face big ends were used and the top piston ring lands were increased from 3/32” to 1/8”
and to reduce a tendency to piston ring flutter and increased oil fling, pressure loading of the
scraper ring was put up to 70 lb/sq.in. 2 b.h.p. was gained by using the solid skirt piston, due to
less friction. Trailing oil way drillings were used on the crankpins to feed oil at a point of
minimum pressure.
The pistons were now solid skirted and of die cast silicon alloy, with the top gas ring chromium
plated. Stronger valve springs met the engine speed of 5,500 r.p.m. KE 965 (EN 54) exhaust
valves combated a neck temperature of 700-800 C., which had caused an XB valve to break
during the 1951 Silverstone Production Car Race. The stems were chromium plated, 0.001 inch
extra clearance given at the guides and the valve tip at the rocker end stellited. With 0.5 millilitre
per litre of lead in the fuel, valve life was approximately 200 hours at 4,500 - 5,500 r.p.m.
An external carburettor balance pipe of 5/8” internal dia. was now required. A Lucas high duty
DVX4A distributor was used, with Lodge plugs in waterproof covers. The crankcase was
stiffened by ribs radiating from the main bearing regions and walls were also stiffened. The
Marston Excelsior oil cooler radiator and reserve fuel tanks were fabricated in aluminium alloy
with a weight reduction of 45 lb. An axle ratio of 4.1 to 1 was employed instead of the former
4.56 to 1. The engine now had a fuel consumption of 0.51 to 0.57 pint/b.h.p. /hour, equal to a
race fuel consumption of 18 m.p.g. and the third consecutive l½ litre class win at Le Mans.
The standard crankshaft broke on test after only 50 hours bench running at 4,200 r.p.m. with
compression ratios above 8 to 1. A crankshaft which had run some 200 hours broke during the
1950 T.T. race when a compression ratio of 8.75 1 was in use. This led to a mathematical
investigation of crankshaft dynamics and the most probable cause of the crank-web bending
fatigue failure was thought to be combined axial and torsional vibrations of the crankshaft
system in conjunction with the presence of an adverse residual stress system in the crankpin fillet
adjacent to the fracture; this residual stress was due to induction hardening of the bearing surfaces
especially if followed by a cold straightening operation allied with stress risers in the
form of a sharp fillet radii and tool marks on the webs. A new crankshaft was developed
incorporating fillet radii on all bearings of not less than 0.100”. The crankpins were also drilled
so as to reduce off centre weight and the magnitude of the bending loads. Great care was also
necessary when induction hardening the crankpins so as to ensure that the hard zone does not
extend into the webs, also that the fillet radii and journal surfaces were free from quenching
cracks.
Experiment showed that Shot peening the fillets could considerably increase the fatigue
resistance using 1/32” dia. chilled shot at 25 to 30 lb/sq.in. the crank being rotated during the
peening operation, also the practice of rolling the fillet by steel balls was effective.
A load diagram on a polar basis was drawn up for big end bearing loads above 4,750 r.pm. and
the serious inertia loading was found to be sufficiently important to warrant drilling the racing
crankshaft.
Besides the l½ litre class victories at Le Mans, first and second places were taken in the l½ litre
class of the 1951 T.T. race and a win at Watkins Glen.
It is particularly satisfactory to learn that almost all the modifications evolved through racing are
found in the current Jowett Series III engine now found in all Javelin and Jupiter cars. These may
be summarised as follows: -
1. Crankshaft - The crankshaft has been redesigned in detail so as to increase its fatigue
strength. The modifications in this direction consist of the crankpins and main bearing
fillets being increased from 0.050” radius, to 0.10” radius, also the hardening technique
has been altered so as to ensure that the hardness does not run into the crank webs where
it may introduce, stress concentrations. The weight of the crankpins has been reduced by
drilling a 7/8” dia. hole through them with the object of reducing the bending load on the
shaft.
2. Oil ways - The oil ways both in the crankshaft and in the crankcase have been modified;
in the case of the crankshaft these have been repositioned so that they emerge on the
crankpins in an area of minimum load, which allows the oil to build up a more stable
film. In the case of the crankcase, the oil ways have been increased in area so as to avoid
any possibility of restriction, especially under cold starting conditions.
3. Bearings - These are now with the exception of the rear main bearings of Vandervell
manufacture and are of the tri-metal type, which consists of a steel backing strip on which
is cast a layer of copper lead alloy; this layer of copper lead is then plated with an
approximately 0.003” thick coating of lead indium alloy which actually acts as a bearing
medium.
4. Crankcase -This has been stiffened by the addition of radial webs on the front, centre and
rear panels, the object of this is to increase the rigidity of the structure which to some
extent will assist in minimising noise.
5. Cylinder heads - The combustion chambers and the ports are polished and the ports are
lined up with the manifold ports. This will improve the gas flow characteristics and will
reduce any tendency towards “run-on”’.
6. Camshaft - An adjustable end location is now provided for this so that individual
adjustment can be carried out to reduce any noise resulting from excessive end float.
7 Cylinder liner bottom seal - This has been redesigned and now consists of an oil and heat
resisting rubber ring trapped between the liner bottom flange and the crankcase. There is
thus a metal to metal contact between the liner bottom flange and the crankcase, which
obviated any tendency to liner shrinkage due to collapse of the bottom joint. This ensures
that the initial liner interference on the gasket is maintained and will result in greater
gasket reliability.
8. Oil Pump - This is now of a submerged pattern, which ensures instant priming under all
starting conditions and the relief is by passed to the suction side of the pump to reduce oil
churning and frothing in the Sump.
9. Pistons - The proportion of the piston ring lands has been increased so as to improve the
fatigue resistance at this point.
10. Sparking plug covers - The original design of bakelite cover with the bayonet fixing has
been deleted and this has been replaced by a moulded rubber cover designed by Messrs.
Lodge for racing motor cycles. This cover is very simple and improved the accessibility
of the sparking plug.
All this development work has been done in the last five years or so and our account covers only
that applied to the engine, this being of such unusual layout as to occasion much interest in how
its teething troubles were overcome. The reader must by now be impressed with the very
thorough testing and research, undertaken by the Jowett engineers and be particularly pleased to
learn how much they owe to racing and competition Work.
The Jowetts with the Series III engine are still well in advance of conventional practice and have
gained in performance and reliability since the brave introduction of the Javelin eight years ago.
Once again, I cannot refrain from observing that at Idle they are anything but idle! - W.B.