Jaguar XK140 specification

This page gives the figures for the model. For the figures for one particular car after rebuild, see WPK38 in figures, which is a different thing and should not be confused with this.

Every figure below carries its source. Where a figure comes from a Jaguar Service Bulletin or the Jaguar Daimler Heritage Trust it is marked factory; where it comes from a club, a marque specialist or a general reference it is marked as such. Where the sources disagree, both are given. Where no acceptable source could be found, the row says so rather than carrying a plausible number.

That last category is larger than it should be, and the reason is set out at the foot of the page.

Engine

Power and torque

Carburation

Note also that the factory's two statements about the SL needle read oppositely — in 1955 it is the needle being replaced, in 1957 it is the weak alternative. Both are published here as found.

Transmission

Moss four-speed, synchromesh on second, third and top.

Reverse ratio: not established, for any of the three.

The JS set carries a caveat: Service Bulletin 214 is dated May 1957, at or after the end of XK140 production, so it is a boundary case rather than an XK140 specification.

Overdrive. Laycock de Normanville, optional, chassis suffix DN. Ratio given as 0.779 by Terry McGrath on jag-lovers — a single source with no factory document behind it. Which gears it operates on, and its oil capacity, are not established.

Automatic. Borg-Warner DG250, three-speed, chassis suffix BW, from 1956. Motor Sport's Earls Court report of November 1956 confirms it in period. Its internal ratios, torque converter multiplication and fluid capacity for the XK140 are not established — the general DG-family figures that circulate cover neither the DG250 specifically nor the Jaguar installation, and should not be used.

On availability, John Elmgreen's figures for right-hand-drive cars are the best on record: no open two-seater automatic at all (nil of 74), seven fixed head coupes of 841, and four dropheads of 480. That is a production count, not a factory restriction, and it says nothing about left-hand-drive cars. It is widely stated that the automatic was never offered on the roadster; we have found no source that actually says so.

Rear axle ratios, all three from Service Bulletin 156, November 1954:

The parts literature complicates this in an interesting way. Rob Reilly, working from the overdrive parts catalogue, notes that 4.09 is the only axle it lists for the XK140; Roger Payne notes that the parts manual carries speedometer part numbers only for the 3.54 and 3.31 axles. Three factory sub-documents, three different subsets. There is no evidence that the axle varied by body style — the documented variable is the transmission.

Propeller shaft type and clutch make, type and diameter: not established. A Borg & Beck single dry plate is universally assumed and we found no acceptable source stating it for the XK140, nor any figure at all for the plate diameter.

Chassis, suspension, steering and brakes

Front suspension. Independent, with transverse wishbones, longitudinal torsion bars, telescopic dampers and an anti-roll bar. The torsion bars are stronger than the XK120's.

The torsion bar diameter and the anti-roll bar diameter are not established. These are two of the most-asked figures about the car and we could not find them in any source we regard as acceptable — not the club pages, not the jag-lovers library or forums, not the marque compilations. They are in the factory's Supplement to Mark VII and XK120 Service Manual for XK 140 (M.3/140) and in the Motor Trader service data sheets, neither of which we have been able to read. See the foot of this page.

Castor and camber figures are likewise not established, though the change point is: the factory altered the castor angle in September 1955, at chassis 800052/811562 (roadster), 804308/814532 (coupe) and 807237/817653 (drophead). The bulletin gives no figure.

Rear suspension. Live axle on semi-elliptic leaf springs, with telescopic dampers replacing the XK120's lever-arm type. One useful fact from the Service Parts List, via bobine.nl: all XK140s used the same spring, part C5721, which was the continued XK120 Special Equipment item. Given how much else varies by body style, that is worth knowing. Leaf count, camber and rate are not established.

Steering. Rack and pinion by Alford & Adler, standard on all XK140s, replacing the XK120's Burman recirculating-ball box. This is the single largest change between the two models and the one owners name first. Turns lock to lock and turning circle: not established.

Brakes. Drums on all four wheels, hydraulic, single circuit — unchanged in principle from the XK120, and every XK140 ever built left the factory on drums. Two factory change points are documented: the fly-off handbrake from September 1956 at chassis 800072/812647, 804767/815755 and 807441/818729; and rear wheel cylinders changed to C39377 in June 1955.

Drum diameter, drum width, lining area, servo arrangement, and master and wheel cylinder bores: not established. The figure "12 in Lockheed" is repeated almost everywhere; we could trace it to exactly one source, which cites nothing. A factory brake servo kit for the coupe is documented to exist, but whether it was standard, optional or coupe-only is unknown.

Wheels and tyres. 16 in, pressed steel disc as standard with rear spats, or Dunlop wire wheels painted or chromed. Disc wheel rims are 5½K — from December 1955 stamped as such in the well, replacing the earlier depressions by the valve hole (Service Bulletin 175). Tyres were Dunlop Road Speed 6.00 × 16; jag-lovers records that every XK120, 140 and 150 left Browns Lane on them, and that the Michelin X was available but not from Jaguar.

Tyre pressures, normal and high speed: not established. The jag-lovers tyres page states outright that its archived material carries no original factory pressures for any XK model.

Dimensions and weights

Wheelbase, length and width are unanimous across every source. Rear track is not: the Jaguar Enthusiasts' Club gives 51.375 in, and one general-reference site gives 51.375 on its 1955 page and 50.5 on its 1957 page, contradicting itself.

On weights, this page declines to give a figure.

The Jaguar Enthusiasts' Club gives 28 cwt for the roadster, 28 cwt for the fixed head coupe and 29 cwt for the drophead — making the steel-roofed coupe exactly as heavy as the open car, and the drophead heaviest of the three. Other sources reverse the ordering entirely, putting both coupes above the roadster. Five mutually inconsistent sets are in circulation and not one of them is attributed to a factory document, the Heritage Trust or a period road test.

One thing is worth saying because it is widely misunderstood. Wikipedia's range of "3,136–3,248 lb" is the club's two round hundredweight figures converted. It is not independent corroboration, and it is routinely cited as though it were a measurement. Behind every weight figure for this car lies a single pair of rounded cwt numbers of unknown origin.

Capacities

This section is nearly empty and the archive would rather say so than fill it. Not one capacity could be traced to a factory handbook, a Heritage Trust document, a club publication or a period road test.

The archive holds one document that lists most of them — the restoration record for WPK38, which gives engine 22 pints, sump only 19 pints, differential 3.5 pints and cooling system 25 pints. Those are not published here as the model's figures, because that document describes one rebuilt car: its gearbox is a fitted Tremec five-speed, its differential has been changed from 4.09 to 3.54, its compression is marked "(estimated) 10.2:1", and its fuel tank line reads "4 Gallons 64 Litres", which is internally contradictory. Several of its other entries look like handbook transcriptions, which makes it a reasonable thing to check against the factory handbook E/101. It is not a substitute for it.

What the road tests measured

Read this section with its limitation in front of you. No period road test was reached directly. Every figure below is a second-hand report of what a period test measured.

Three things follow, and all three matter more than the numbers.

First, all four identifiable tests are of the MC — the Special Equipment car with the C-type head — and three of them are of US-market cars. No test of a standard-specification XK140 was found, and no UK road test figures at all, for any body style. Figures from an American MC should not be presented as "the XK140's".

Second, the club's own top speed is the wrong number. The Jaguar Enthusiasts' Club gives 121.1 mph as a top speed, unattributed. That was Road & Track's best one-way run. The two-way mean — which is what a road test's "maximum speed" conventionally means — was 120.3 mph. Somewhere along the way the better of two numbers was quietly promoted.

Third, 125 mph never happened. The Heritage Trust's own page says the car would do "in the region of 125 mph", and other sites print a flat 125. The highest measured figure anywhere in the record above is a 124 mph best one-way run. 125 mph is a manufacturer's claim that has hardened into a measurement.

Not established for any test: gear maxima in first, second or third; a standing quarter mile tied to a named test; measured fuel consumption tied to a named test; any figure for a drophead coupe; and the numeric table from The Autocar's 1955 coupe test, which is confirmed to exist — the Jaguar Drivers' Club quotes from it — but which is nowhere online.

The commonly quoted 0–60 of 8.4 seconds, the standing quarter of 16.6 to 16.9 seconds, the 0–100 of 26.5 seconds and the 16 to 18 mpg are all either unattributed or attached to no test at all.

Prices as new

Two limits on the roadster figure. The Trust says "without extras", which does not tell us whether the figure includes purchase tax, and we could not establish that either way. And the figure is undated on the Trust's page; the page describes a 1954 car, but that may be a launch price or a later one.

On £1,575. A figure of £1,575 including 50% purchase tax has been given to this archive and we could not connect it to anything — not to any Heritage Trust page, not to the Earls Court show reports of November 1955 or November 1956, which print no XK140 prices at all, and not to any club page or period document reachable from here.

One observation, offered as a hypothesis rather than a finding: a bare £1,575 with no shillings and pence has the shape of a basic price before purchase tax, or of a rounded secondary retelling. UK tax-paid prices of this period are almost always quoted to the penny, as both established XK140 figures are. A tax-paid roadster at £1,598 8s 4d and a round £1,575 are unlikely to be two prices for the same thing. Until someone reads it off a period price list, it is recorded here as a figure of unknown origin rather than as a price.

UK list prices by body style are simply not on the open web for this car. The natural sources — the October and November price lists in The Autocar and The Motor for 1954, 1955 and 1956, and the SMMT Motor Show catalogues — are not digitised.

Why so much of this page says "not established"

Not because the record is thin. Because the documents that hold these figures are not readable as text.

Two of them are online now, as page scans, and anyone with a browser can read them.

The Motor Trader service data sheets for the XK140, eight pages, about 1955, held at jag-lovers and again at Unique Cars and Parts. A trade service data sheet of this period carries exactly the panel this page is missing: torsion bar and anti-roll bar sizes, brake drum and lining dimensions, every fluid capacity, tyre pressures normal and high-speed, turns lock to lock, turning circle, clutch size, propeller shaft type, and full tune-up data including plug and contact breaker gaps.

The 1955 UK sales brochure, sixteen pages with fourteen imaged, also at jag-lovers. Jaguar brochures of this period generally carry a specification panel and sometimes prices by body style — the natural home for the missing coupe and drophead prices, the per-body-style weights and heights, and the ground clearance.

The rest are factory publications that are not digitised at all:

Motor Sport's archive is fully digitised and searchable, and contains no XK140 road test. That is a useful negative result: nobody need keep looking there.

If you hold any of these documents, or can read the two scans above, this archive would be glad to hear from you. Every gap on this page is a gap that somebody could close in an afternoon.