Jaguar XK120 Buying Guide
Even more characterful than an E-type – but you really need to know what you're looking for when buying an XK120
How much to pay
• Project £40,000-75,500 • Good £80,000-120,000 • Concours £145,000+ •
Running costs ★★★
DIY Friendly ★★★
In Britain, austerity lasted for years after the end of World War 2. Yet, in the midst of rationing and national service, Jaguar launched a car for 1948 that appeared fast and stylish; yet vaguely attainable at the same time. Designed to showcase the all-new 3.4-litre straight-six twin-cam engine, the XK120 was one of the most important cars ever to come out of Britain.
With its incredible shape and equally impressive performance, the XK120 was nothing short of a sensation. However, Jaguar tooled up for only a handful of cars, expecting few takers for this sleek two-seater sports car. Unsurprisingly, demand was off the scale and the XK would remain in production for more than a decade, in one form or another. Later would come the XK140 and XK150, but the XK120 in its various forms is genesis for those of a Brown's Lane persuasion – and there are more of them than you might think.
Your AutoClassics Jaguar XK120 inspection checklist
The XK engine will notch up 100,000 miles between rebuilds if it’s looked after, but neglect can cut this mileage right down. Regular oil changes are the key, along with maintaining the anti-freeze concentration to prevent internal corrosion of the cylinder head.
A worn XK engine will display all the signs of needing a rebuild: blue smoke from the exhaust and low oil pressure. There should be at least 50psi at 3000rpm, although oil pressure gauges are notoriously unreliable.
Keeping on top of the cooling system is essential, as fixing an overheated engine is costly. An electric fan behind the radiator is worthwhile as is fitting an expansion tank – but only if there are no underlying issues that need to be fixed first.
Even a DIY rebuild of an XK engine is costly; opt for a professional overhaul and the bill will be eye-wateringly large. Thanks to poor access, removing the engine is involved for even simple jobs, so budget for the work if it's destined as a specialist job.
The Moss manual gearbox is strong and features synchromesh on second, third and fourth. The synchro is part of the gear itself, and replacement parts were unavailable until recently, but they’re now being manufactured – for a price. Worn layshafts and roller bearings are another possibility but these are available from most stockists.
For years the Moss gearbox suffered poor parts availability and it’s far from the nicest transmission to use, which is why some cars have been converted to a modern five-speed gearbox (such as a Getrag unit), but some of these are now suffering from poor parts supply too.
Suspension and brakes
The rear leaf springs sag with age, but it’s possible to get them retempered. There should be an inch between the top of the tyre and the wheelarch; if it’s less, expect to have to invest in some rebuilt springs soon.
The front suspension also gets tired and it can be costly overhauling it all. Just to replace all the bushes with polyurethane items and replace the various joints and lever arm dampers will soon add up.
There’s little to worry about with the braking system as it’s all conventional, so it’s just a question of making the usual checks for wear or a lack of maintenance. The front drum brakes can be swapped for discs, but the handbrake works better with drums at the back, and the extra braking power isn’t really needed.
Don’t assume that an XK is sound just because it looks it. Front and rear wings rot (especially the lower portions), the sloping boot fills up with water and the sealing panel fails inside the rear wings, leading to rotten B-posts. The sills also dissolve, along with the outriggers and A-posts.
The rear wings are bolted on and are often pulled into place by their retaining bolts, leading to distortion. Look along the top of the wings, which should have a smooth curve along with body-coloured beading where the wings meet the bodyshell.
Panel gaps can be all over the place, with doors prone to dropping when their hinges wear – although the same symptom can be down to rotten A-posts or door frames, which is a far bigger problem. The XK120 has wooden-framed doors and the bootlid also has a timber frame which rots, leading to distortion of the panel.
The chassis is reasonably robust, but the anti-roll bar mounts rot away and repairs are surprisingly costly. The front mounts for the rear leaf springs are even more expensive to repair. New chassis are available but it’s always better to repair an original if possible, to preserve originality and value.
Everything is available to retrim an XK interior and most of the interior and exterior brightwork is also available new, but costs can be high and fettling is often required to get a perfect fit. Check that everything is there and in good condition; you’re often better off reviving an original part than just buying new.
The XK120 was originally positive earth with two six-volt batteries; many are now negative earth with a 12-volt battery and an alternator. Most electrical items are readily available as they’re also fitted to numerous other classics. However, some bits are costly and/or hard to find, such as fuel sender units – and these are also notoriously inaccurate.
Incorrect instrumentation is common as the proper Smiths gauges are no longer available. Also check the state of the wiring; the bullet connectors often play up while looms are now getting old and going brittle, even if they’ve already been replaced once. Electrical modifications are common and many are poorly carried out, leading to current drains that are hard to trace. Missing grommets aren’t unusual either, along with the resulting short circuits.
- 1948: The XK120 makes its debut at the Earls Court motor show in October, with a 3442cc twin-cam straight-six. The first XKs are bodied in aluminium, Jaguar having needed to save money when creating the tooling.
- 1950: Jaguar is taken aback by demand for its sportscar and commits to creating tooling to make the car with steel panelling. As a result, after 242 have been made with aluminium panels, there’s a move to steel instead.
- 1951: Production of the Fixed-Head Coupé starts in July, and there’s also now a Special Equipment (SE) option which brings a high-lift camshaft, lightened flywheel, uprated valve springs, high-compression pistons, stiffer torsion bars and rear leaf springs, wire wheels and a twin exhaust system. The result is an increase in power from 160bhp to 180bhp. A heater is now standard.
- 1953: In January, production of the Drophead Coupé begins. The new car gets winding windows and a heavily lined hood for decent refinement when cruising.
- 1954: The XK120 is superseded by the XK140, which features more cabin space, thicker bumpers and the adoption of rack-and-pinion steering. Indicators are now fitted; the XK120 did without.
If you’re looking for a classic that will be accepted anywhere, few options fit the bill like a Jaguar XK120. Brimming with British charm, the XK120 has looks, glamour, heritage and pace in its favour, but this is a car from the 1940s and it feels like it.
The XK120 is rarer than you might think; just 12,078 were made and most went to the US, so original RHD cars are really unusual. However, the 120 is the most numerous of the XKs, with 8884 XK140s and 9395 XK150s also produced. Those later cars are all more usable though, thanks to improved mechanicals and bigger cabins.
Because the XK120 is relatively light it feels very brisk, but drive a car in completely standard form and you’ll soon see why so many owners upgrade the brakes, steering and suspension; the driving experience is distinctly vintage. Other upgrades that increase usability include electronic ignition, an electric fan, an alternator conversion and electric power steering. However, don’t assume you need a significantly modified car; for many XK120 owners, part of the charm is the genuine 1948 driving experience, complete with crossply tyres.
If you’re buying a car that’s been restored, make sure the work has been done by someone reputable, who ideally will have refurbished parts rather than replaced everything wholesale. Having said that, overhauling the original gearbox or suspension tends to cost the same as fitting modern upgrades – but the latter is far more desirable.
The ultra-rare alloy-bodied XK120 came in OTS (Open Two Seater) form only, which means rudimentary weather protection. Steel-bodied cars were built in OTS, DHC and FHC forms.
The Drophead Coupé should be weathertight and offers the best of both worlds for touring; top-down driving with roof-up protection. The Fixed-Head Coupé offers refined cross-country driving. All editions are desirable, but don’t be led too easily on which is right for you. Try them all and work out which one suits you best; you might find it’s all of them.
Picture courtesy of MagicCarPics
Looking to buy a Jaguar XK120?
The Jaguar XK120 was the first post war sports car to be built following Jaguars hugely successful SS100. The XK120 was launched at the 1948 London Motor Show as the test-bed and show car for the new Jaguar 3.4 litre six cylinder XK engine. The alloy cylinder head, twin side-draft SU carburettors and duel overhead-cam 3.4 litre unit produced a staggering 180bhp. The XK 120 proved an instant hit an