When the Jaguar D-type made its racing debut in the 1954 Le Mans 24-hour race, it marked a complete departure from the XK 12—based C-types which had won the race in 1951 and 1953. instead of the C-type’s space-frame the D-type had a central monocoque tub in 18 gauge magnesium alloy, with holes cut in to house driver and “passenger”. A tubular aluminium subframe argon arc-welded to it carried the engine and wishbone/torsion bar front suspension. The 3,442 c.c. XK engine was mounted at eight deg. To the vertical, carried triple 45mm twin-choke horizontal Weber carburettors and had dry-sump lubrication to halve the sump depth and reduce frontal area. There was no flywheel, just a large torsional vibration damper at the front of the engine; the starter ring was formed on the outer casing of the triple plate clutch. The gearbox was a new four-speed all-synchromesh one of Jaguar manufacture. Dunlop disc brakes all round were assisted by a Plessey servo pump driven by the propshaft. The live rear axle was located by four steel-plate trailing links and controlled by a single transverse torsion bar, an A-bracket and telescopic shock-absorbers. The whole was cloaked in aluminium to shape designed by aerodynamicist Malcolm Sayer.
Six D-types were made by the works in 1954, with chassis numbers from KXC 401 (XKD came later) to 406. The dark green XKC 402, 403 and 404 (registered OKV 1, 2, and 3) were entered at Le Mans for Rolt/Hamilton, Moss/Walker and Whitehead/Wharton respectively. All three cars suffered from blocked fuel filters and the last two pairings retired with brake and engine problems. Rolt/Hamilton fought on to finish second, only 2½ miles behind the Ferrari of Gonzalez/Trintignant.
The first D-type victory came in the Reims 12-hour race in July 1954, won by Peter Whitehead/Ken Wharton (XKC 404). Afterwards the D-type was to gain countless victories throughout the world, but it was Le Mans which made the car a legend, with a hat-trick of wins in 1955 (Hawtorn/Bueb, XKD 505), 1956 (Flockhart/Sanderson, Ecurie Ecosse, XKD 501) and 1957 (Flockhart/Bueb, Ecurie Ecosse, XKD 606) when D-types finished 1st, 2nd, 3rd, 4th and 6th.
In 1955 a D-type production line was set up at the factory, which turned out 67 D-types, inclusive of 16 XK SSs, the road-going development of the D-type. In addition, eight more were built by the Competitions shop in 1955, five for the works (XKD 504 to 508), two for Ecurie Ecosse (XKD 501 and 502), while XKD 503 went to Equipe National Belge. The last six D-types, XKD 601 to 606, were built in the Competitions Shop in early 1956. In total, 71 true D-types were produced, plus 16 XK SSs.
After the first six cars of 1954, all D-types were produced with bolt-on steel front subframes to facilitate repair. Factory cars from 1955 were fitted with the “long-nose” bonnet (adding 7½in. to the length of the car), with twin brake cooling ducts and a longer tail fin. All production (and other non-works) D-types had short-nose bonnets. (Short) tail fins were an option on the production cars. All factory cars from 1955 were fitted with “wide angle”, bi-valve cylinder heads, with exhaust valves inclined to 40 deg. And inlets at the standard 35 deg. angle to prevent valve overlap. Production cars had standard angle heads. Normal capacity was 3,442 c.c., but two 2.4-litre cars ran in the 1954 Tourist Trophy and 3-litre engines were also seen in D-types. Later works engines were of 3,781 c.c. with Lucas fuel injection; in 1957 works Sebring tune these produced 306 b.h.p. at 5,500 r.p.m. – C.R.