1979 Jaguar XJ-6 L
6-cyl. 4235cc/176hp EFI
With an experienced team and a lot of data.
Upon its introduction in 1968, the new Jaguar XJ-6 replaced all the sedans which preceded it. The signature 4.2-liter DOHC six-cylinder engine delivered 180 hp and was matched with anti-dive suspension, power rack-and-pinion steering, power disc brakes, and either an automatic or manual 4-speed transmission with overdrive. Inside there were leather seats, walnut fascias, and enough gauges for a small plane. An up-market sibling, the six-cylinder Daimler Sovereign, was introduced in 1969.
The XJ-6 was the last Jaguar designed by company founder William Lyons, and it was a fine balance of refinement, luxury, and performance. Handling was superb for a four-door sedan.
The first series XJ-12 (and its Daimler Double Six cousin) followed in 1972, using the SIII E-Type’s 5.3-liter motor. Air conditioning was standard, but no manual transmission was offered. Fuel injection replaced the quad carbs and boosted the V-12’s 244 hp to 285 hp in 1975 in the second series XJ-12, and the collectible two-door coupe was introduced the same year in both 6-cylinder and V-12 configurations. Neither was very popular with the buying public when new, so today these particular body styles are much sought after.
A final redesign to the initial XJ run occurred in 1979, courtesy of Pininfarina, who raised the Series III XJ-6 and XJ-12 roof at the rear and added a “kick” to the back fender. Additionally, quality control improved significantly during third series production. By 1987 the XJ-40 replaced the XJ-40, while the XJ-12 soldiered on until 1991. Daimler Double Six models were built alongside the Jaguars, with bespoke interior and vinyl roofs, and the very last V-12 was a Daimler Double Six in 1992.
Enthusiasts tend to gravitate towards the 4.2-liter six-cylinder today simply because they are much easier to work on. They are mostly reliable, too, although cars equipped with air conditioning tend to be more inclined to cylinder head gasket failures. Look for cars that have been regularly exercised.
The V-12 engine, on the other hand, is much more difficult to maintain. Overheating issues from mild to drastic can result from high underhood temperatures. Much like the V-12-powered Jaguar XJS, the biggest single problem to be aware of on an XJ-12 involves the fuel system, where fuel vaporizing and over-pressurizing fuel hoses can occur when the car is switched off after a hot drive, potentially leading to engine fires.
While it is a bit more persnickety, the Jaguar V-12 carries with it considerable cachet, and it is silky smooth when found in good tune, which makes it an appealing option. Good XJ-12s can be difficult to locate, though and rough cars should be only a last resort. The wisdom of buying the best car possible was never truer, and even very low mileage examples remain affordably priced.