www.jec.org.uk

As I'm fairly new to this and one of the cars is older than me, what is the fuss about pre HE. I have a 1976 Xj-s 5.3 and apart from the large amount of rubber bumpers, they very similar to the later models.
apologies if I have offended anyone.........

None taken, we all started somewhere, in my own case nearly twenty years ago.......

Pre and post HE refers to the implementation of Michael May's "Fireball" cylinder heads (High Efficiency = HE) on the XJ-S which reduced fuel consumption from Oh My Gawd to Ouch! This came in in 1981 and hence cars are referred to as Pre or Post HE.

I can highly recommend our own Nigel Thorley's book, "You and your Jaguar XJS", Haynes Publishing, as an essential read, especially if you are unfamiliar with the history and development of this fantastic car.

Best
TonyS

The XJS got off to a bad start in 1975 as it was considered to be a softer and inferior replacement for the E-type with rather strange body styling, but it had impeccable provenance having been designed aerodynamically by Malcolm Sayer with a more efficient body than the E-type, and also being the last car with which Sir William was involved before his retirement.

The V12 engine was a great piece of engineering which gave the car serious performance, but its thirst was wicked and reports of 10 to the gallon were not unusual. As the years rolled on and the political situation became more uncertain it was decided that something had to be done to make the car what we would now call 'more PC', so a new cylinder head with more efficient gas flow and new combustion chamber shape was designed by May which improved the mpg, but not dramatically as it only went to the mid teens after all the work. Nevertheless it became known as the High Efficiency (or HE) head. That was in 1981, so cars before then are known as 'pre HE'.

Hope that explains it. Get yourself the booklet 'History of the Jaguar XJ-S' from Heritage Trust and have a proper read about the whole scene.

As others have said, the HE part refers to new, more efficient cylinder heads which gave better efficiency and allowed a change of differential ratio to 2.88:1 which made the car more long legged and improved mpg from ruinous guzzler to just a heavy drinker!
At the same time there were a large number of interior and exterior changes aimed at making the XJ-S more of a traditional Jag. So things like chrome bumpers, starfish alloys and wooden dash inserts were added.
It was also around this time that John Egan took the Jaguar helm and led a big drive to improve quality and reliability.
If you'd like to read up on the history of the XJ-S then there are several excellent books available from Paul Skilleter, Brian Long and, as mentioned, Nigel Thorley.
Hope that helps

Neddie,

As others have mentions, Nigel's book is a comprehensive great read. If you want a 2-minute read on XJS history have a look at the "Model Info" page in the XJS Forum pages on the website.

Somewhat paradoxically to the efficiency of the HE-head, the most powerful 5.3 engines are deemed to be the P-digital equipped cars of 1980 using the old cylinder heads.

I have just restored a 77 pre he with manual gearbox. Apparantly the rarest of all xj-s`only 300 odd built. The big difference as well as head design is the fuel injection system which is based on Bosch D-Jetronic and the Lucas ignition also known as "The Prince of Darkness" Mine is still on the three wire reed switch trigger board, even rarer apparently.
I have driven both he and pre he and think the he is better around town (auto though) the manual box is a bit clunky and not up for quick changes however you can leave it in top right down to 500 revs and it will pull away quite happily.
My speedo cable is busted and the fuel sender is seized so i use a satnav and keep the tank full. I worked to fuel cons to be around 16mpg.
He seems to deliver its power throughout the range but not too keen on 5200 + revs whereas the pre he does hee haw until around 2800 revs, until then it feels like huge turbo lag when up comes the nose and your off, keep it between 3000 and 6000 revs and it really motors, quite a bit quicker than the HE.
Mine is shot as far as handling goes, a combination of original bushes/shocks on the front, new bushes and hard shocks on the rear (too hard imo) and ancient Avon Turbospeeds that are as hard as a hoors heart mean its been straght line stuff, none of this cornering at speed business until it has had all the rubbery bits replaced.
I am firmly a pre he convert Apparently i`m PRE HEstoric.
Have a read of my thread a bit further down "pre he man xjs"