Jowett Jupiter Buyer’s guide

The Jowett Jupiter was a clever, innovative small sporting car that proved effective and reliable in competition. It sold in small numbers simply because its maker lacked the resources to build it cheaply enough.

Forced to produce cars for export or die after WW2, Britain’s car manufacturers battled with outdated equipment and desperate material shortages. Gerald Palmer’s brilliant Javelin saloon – aerodynamic, monocoque, low forward-mounted flat-four engine – was a revelation, but overseas sales were slow. The potential for a sports car derivative was seen both within and outside Jowett, however. Influence from Lawrence Pomeroy of The Motor and ERA resulted in a joint project to bring Austrian Prof Eberan von Eberhorst, designer of the phenomenal pre-war Auto Union Type D, over from Italy to join ERA and design a sports car for Jowett.

Von Eberhorst was horrified by the primitive nature of the ERA works but, undeterred, sketched a tubular chassis on the floor with chalk. Novel and stiff, it employed torsion-bar suspension all round with trailing-arm rear-axle location, plus anti-roll bars front and rear (deleted for production). Displayed at the Motor Show in ’1949, before a body was ready, it attracted attention and resulted in quite a few Jupiter rolling chassis being sold to coachbuilders large and small. Jowett chief designer Reg Korner drew up a rakish two/three-seater soft-top body, which was specified with wind-up windows and a quality stowaway hood because it was clear from the start that Jowett could not compete on price with the likes of the MG TD. Steel was used for the inner body frame, but all the outer panels were pressed in aluminium (which was not subject to the strict government tariffs placed on steel supplies), then individually panel-beaten to fit.

It was an expensive car to build and, when the Healey 100 was launched in ’1952 for just £39 more, its days were numbered. The substantially cheaper Triumph TR2 nailed its coffin shut in ’1953. Jowett bravely tried to introduce the smaller, lighter, more sporting R4 (which may well have been the first production car fitted with an electric cooling fan and thermostatic control), but had to call it a day. The factory was sold to International Harvester and Jowett faded into history. Jupiters now have outstanding club support and make an excellent classic buy, offering comfort and practicality that belies their age.

Chassis at ’1949 Earls Court show; 75 had coachbuilt bodies. Wisdom/Wise lead Bobek/Netusil Škoda at 1950 Le Mans.

Jowett had early production issues with head gaskets and crankshafts on the wet-liner flat-four engine, although all of these problems have long since been resolved and there are no inherent weaknesses with the unit. Oil cooler was standard but its location was moved from in front of radiator (at back of motor) in 1952.

Original Smiths gauges are unobtainable new and costly to recondition, so look for a full set in good order. Alternative or repro instruments never look quite right.

Standard Zenith carburettors are often replaced by Webers or, as here, Dell’Ortos that are available new and release a little more power than rebuilt Zeniths can.

Gearchange should be precise (if not, selectors need adjusting). Test for poor synchro (on 2/3/4) and jumping out of gear, indicating the need for an overhaul.

Front suspension needs lubrication every 500 miles (11 grease points), or kingpins will wear and start to seize (stiff steering). A rebuild is expensive.

The quick, easy to erect hood and sturdy wind-up windows make the Jupiter practical. Check condition and alignment of frame, hood cover and wood sections.

Wide leather seat and column shift meant three could be carried at a pinch, or two in comfort. On Mk1s it hinged forward for access to the luggage space.

Rot spots

Transverse chassis tube

Cracks in engine bearer tubes, if not reinforced

Steel bulkhead

Electrolytic corrosion where aluminium meets steel

Steel A-posts

Steel floors, especially six mounting points to chassis

Steel sills

Bottom of aluminium panel behind door (water trap)

Chassis cracks where

Panhard rod mounts

Transverse chassis tube

Curvaceous Jupiter rides and handles much better than you would expect a ’50s sports car to, with its chassis designed by Eberan von Eberhorst.

On the road

A good Jupiter should feel lively and relatively modern to drive, with a throaty, almost Subarulike exhaust note from the water-cooled flat-four. An oil cooler is standard and the large radiator is set behind the engine. Check for signs of overheating and leaks – radiators do silt up with age and neglect will ultimately lead to headgasket issues. Look for emulsion in the oil and radiator. Most (but not all) engines leak a little oil; check it’s not excessive and that the unit is not blowing oil smoke everywhere, indicating worn bores and rings. Listen for knocking under acceleration, which means crankshaft wear.

With a little practice, the column gearchange is easy to use and, while shifts shouldn’t be rushed, the Jupiter can be rowed along effectively because its ratios are well chosen. Listen for gearbox bearing wear (dip the clutch at tickover) and test for worn synchros and jumping out of gear. Vibration from the drivetrain is likely to be a worn Layrub coupling – the forward-mounted engine means an unusually long, split propshaft. The Jupiter should handle well, with light, precise steering and a comfortable ride thanks to its sophisticated long-travel suspension, which does, like all ’50s cars, need frequent lubrication.

Though the electrics are straightforward, it’s wise to inspect the condition of the wiring loom, because it may be dangerously hard and/or frayed in places if it’s the original. New looms are available but time-consuming to fit. Some cars, such as the one photographed, have had their original trafficators removed and flashing indicators fitted; it’s worthwhile for safety, if not originality.

Well-equipped dashboard, with big rev counter and speedo


Greg Jackson

“Jupiters have always been part of the family,” says Jackson, laughing. “My dad had them first. My brother bought this one as a non-runner for £35 in 1965. Dad towed it a couple of miles then opened the bonnet, tweaked the distributor and it fired up! I bought it from my brother and have had it 50 years, it was my everyday car for many years. It’s been uprated with Dell’Orto carbs and, when the engine was rebuilt, with Fiesta pistons. The skirts have to be modified slightly but they give higher compression and a bit more power. The Jowett Car Club is fantastic for parts; if I order on a Monday evening, they’re here on the Wednesday. It gets batches made and I have a good stock of used spares. It’s very friendly, too – we enjoy several trips with them every year.”

The knowledge


Show/rebuilt £30,000

Average £20,000

Restoration £8000


New, uprated water pump £450

Rebuilt radiator (exchange) £225

Brake master cylinder (exchange) £200

Brake shoes (axle set, exchange) £40

Centre grille £300

Stainless-steel exhaust system £420


Jowett Car Club 07971 966136;

Jupiter Owners’ Auto Club


The Jowett Jupiter Edmund Nankivell, Veloce Jowett Jupiter Special Body Nankivell, Penmellyn Jowett Javelin & Jupiter Nankivell & Geoff McAuley, Crowood


Jowett Car Club Spares 01535 692002 (members only)

JOAC Spares 01588 638469

Bill Lock 020 8390 7904

Dennis Sparrow 020 8579 1776

Drummond Black [email protected]

Kip Motor Co 001 972 243 0440

Scott Renner [email protected]

One to buy £24,500

Year of manufacture 1952

Recorded mileage 90,896

Vendor Greg Jackson, Stockport; tel 07902 919949

For Attractive and eminently usable

Against Noticeable paint defects

Non-original blue suits Jupiter but paint has a few flaws. All the gauges function, plus the hide is in nice condition. Oil-tight flat-four has covered 15,000 miles since rebuild.

The owner of our featured car, Jackson picked up this Jupiter two years ago as a retirement project. The previous enthusiast owner had looked after it for more than 20 years and enjoyed occasional continental tours, but it was hard to start and the suspension was incorrectly set up. The car now fires readily and handles well.

Still on the original Zenith carbs, the flat-four pulls strongly, the gearchange is precise and the light steering a delight. The tyres are relatively new, plus the engine and transmission oil-tight. The body was painted in ’1991 in a non-original metallic blue. The then owner added blue piping to the cream leather seats (which are in excellent order), and painted the crank pulley, air filters and horns to match. Otherwise the engine bay is very original. The top hose might benefit from replacement soon and there is a rattle from a loose exhaust baffle. The dashboard is lovely, with all of the correct instruments working.

Underneath, it’s all properly painted and in very good condition; angle-iron stiffeners have been welded under the front of the chassis tubes, a mod recommended by Jupiter pundits. On top, the car looks stunning from a distance but closer inspection reveals several areas of surface corrosion under the paint, especially adjacent to the wing piping front and rear. You could live with the car and enjoy it as-is for years, but it would need a bare-metal respray to make it really nice.


1949 Oct Chassis unveiled at Earls Court

1950 Apr Jupiter launched at New York show

1950 Jun Jupiter wins class at Le Mans

1951 Apr Left-hand-drive version introduced; ashframed aluminium hardtop available for standard Jupiter by WM Park (GRP top later offered in USA)

1951 Jun Light sports R1 built for Le Mans, and wins class (also 1952); three built

1952 Apr Engine side valances attached to bonnet instead of chassis; oil cooler moves from ahead of radiator to front of engine

1952 Oct Mk1A arrives: external-opening larger boot, longer cabin, smaller fuel tank, symmetrical metal-face dash in place of handed walnut

1953 Oct Jupiter R4 introduced, new deep box chassis, cam steering, leaf rear springs, welded-on sports-racing body, 8.5:1 CR, overdrive; three built

1954 Nov Last Jupiter produced, using the original 1949 London Motor Show chassis


Sold/number built 1950-’1954/825 + 75 chassis

Construction chrome-molybdenum tubular chassis with steel and aluminium two-door body

Engine all-iron overhead-valve 1486cc flat-four, with twin Zenith carburettors

Max power 60bhp @ 4750rpm-65bhp @ 5000rpm

Max torque 84lb ft @ 3000rpm

Transmission four-speed, three-synchro manual, driving rear wheels

Suspension: front unequal-length transverse links rear live axle, four parallel trailing arms, Panhard rod; torsion bars, telescopic dampers f/r

Steering rack and pinion, 2 ¾ turns lock-lock

Brakes Girling hydraulic 9in drums f/r (first c56 chassis only, hydraulic front/mechanical rear)

Length 14ft (4267mm)

Width 5ft 2in (1575mm)

Height 4ft 8in (1422mm)

Wheelbase 7ft 9in (2362mm)

Weight 2100lb (955kg)

0-60mph 14.2 secs

Top speed 89mph

Mpg 22-30

Price new £1284 (1952)


£114.95, for a 30-year-old Londoner, with full no-claims and a clean licence on a 1952 Jupiter as a garaged second car, agreed value £23,000, 5000 limited mileage. Lancaster: 01480 484848.



The 2.1-litre Standardengined Plus Four was Morgan’s only model from ’1951 in 2str, 4str or DHC forms, the last closest in concept to Jupiter.

Pre-war styling and handling, with similar pace.

Sold/no built 1950-’1958/245

Mpg 25-35

0-60mph 14.1 secs

Top speed 85mph

Price new £880-965 (1952)

Now £17-25,000


Not that quick given its 1497cc overhead-cam engine, the SM was (and still is) quite a bargain, especially with pricecutting during production. Most went for export.

Sold/no built 1951-’1955/3440

Mpg 27-37

0-60mph 20.2 secs

Top speed 77mph

Price new c£950 (1952)

Price now £6-10,000

Jowett’s attractive styling was barely altered over its four-year production run.

Our verdict

Considering their relative prices when new and the quality of construction, Jupiters are undervalued against other ’50s sports cars. Whether you’re after a project or a concours example, it’s important to check carefully for originality and missing parts. With decent weather protection and good performance, they make ideal touring cars as well as competitive rally mounts.


• Ahead of its time

• Comfortable; efficient weather protection

• Good handling and usable performance; keeps up with modern traffic

• Fine spares supply from enthusiastic club


• Many have been modified, not all well

• Original panels and instruments hard to find

• Costly to restore due to complex construction

How useful was this post?

Click on a star to rate it!

Average rating 4.3 / 5. Vote count: 31

No votes so far! Be the first to rate this post.