Discussion
Superb shot of what looks to be a powder blue ? Early 1970 2.8 model.
I saw a p blue one on Sunday, first XJ 6 I've seen in that colour for a long time and it's bought some great / but sad memories flooding back.
In 79, a Late pal Darren, had the use of his Trader Dads, lovely green J reg 2.8 Litre example and on a Thursday morning, for his day release course, another student plus me in the back, would be subjected to a "quick" blast to Loughton college in it. I can still remember being shocked at how fast it was, when he used to boot it down Rangers Rd ( which used to be a fast stretch of road in Epping Forest ) and particularly when I had a tear up with him one day, on my tweaked Kawasaki H1F 500. I wanted to buy it, but i was broke back then. Sadly after a few months he blew the Jags engine up.
R.I.P. Darren.
Edited by neutral 3 on Tuesday 7th May 11:50
Edited by neutral 3 on Tuesday 7th May 11:50
Edited by neutral 3 on Tuesday 7th May 18:40
I regret selling my October '73 built SWB 4.2 manual with overdrive two and a half years ago, for an early '70s Jag it was remarkably solid and rot free. I spent about £3k refreshing the exhaust, cooling system, suspension, ignition etc and it rode like nothing else I've ever driven or been a passenger in. I sold it to buy another bloody Mini which is also now gone, silly me. The Jag is now in Norway, it was bought my a TV producer who wanted an early Series 2 to compliment his near identical Series 1. In some ways I regret it even more than selling my last P5B Coupe which I loved to bits and really bonded with...
P5BNij said:
I regret selling my October '73 built SWB 4.2 manual with overdrive two and a half years ago, for an early '70s Jag it was remarkably solid and rot free. I spent about £3k refreshing the exhaust, cooling system, suspension, ignition etc and it rode like nothing else I've ever driven or been a passenger in. I sold it to buy another bloody Mini which is also now gone, silly me. The Jag is now in Norway, it was bought my a TV producer who wanted an early Series 2 to compliment his near identical Series 1. In some ways I regret it even more than selling my last P5B Coupe which I loved to bits and really bonded with...
Regency red. What a shame you sold it. It does look a lovely example. I do know of a really nice / original regency red / biscuit S.1 that may be for sale.
Thinking back, that brg one that my pal used to hoon about in, was a manual / over drive car.
neutral 3 said:
Mike-tf3n0 said:
The 2.8s used to do that, it was a pre ignition problem if I recall.
Piston holers! Daren's Late Dad had a garage in Highams Park and I remember him saying that when he pulled the head off, several pistons were holed!The problem didn't occure on the 4.2s as they had longer strokes, shorter dwell times and (AIUI) flat-topped pistons. The problem wasn't picked up in testing because Jaguar did nearly all their test miles at high speeds and high loads, thinking that that would be the most punishing regime for the engines. The 2.8 passed those tests easily, but the classic failure mode in the early 1970s was an XK6 which had been bumbling around town for a few days (and thus building up a nice layer of lead and soot on the piston crowns) having sudden and catastrophic engine failure as it accelerated down a motorway sliproad for the first time in a while. Hard acceleration got the combustion temperatures up and created the pre-ignition problem. If the hard acceleration was brief enough the engine would survive and the deposits would be burnt off in high-speed/low-load cruising. But prolonged hard acceleration would keep the piston temperatures high enough for long enough for the 'hot spots' to develop and burn out the crown.
I believe the fix was fitting flat-top pistons and altering the ignition advance mechanism for the 2.8s to reduce the advance of the ignition under high vacuum conditions. I suspect it wouldn't be so much of a problem in these days of lead-free petrol, either.
Here's a Series 1 XJ6 I was fortunate enough to drive last year - suitably enough it started life as a 2.8, had two engine failures (one under warranty). When the second 2.8 engine expired the owner paid a Jaguar main dealer to convert it to 4.2, plus the brake/transmission changes from 2.8 to 4.2 so it became, as close as makes any difference, a 'genuine' 4.2 manual o/d.
Lovely, lovely thing, even by the standards of Series 1 XJ6s which are one of my absolute favourite cars.
2xChevrons said:
The 2.8 problem was carbon/lead deposit buildup on the piston crowns in low-speed, low-load operation, coupled to the relatively high dwell time at TDC (where the piston is essentially stationary as it reverses direction at the top of its stroke) due to the 2.8's short stroke. I believe the 2.8s also had a convex piston crown to bump up the compression ratio. So you had an engine with a piston crown which was close to the spark plug and spent a lot of time at TDC. This meant that any hot spots created by carbon/lead buildup on the piston crown were better-placed to pre-ignite the mixture, which caused shock-damage to the piston crown and made the pre-existing hot-spots to overheat and burn a hole in the piston.
The problem didn't occure on the 4.2s as they had longer strokes, shorter dwell times and (AIUI) flat-topped pistons. The problem wasn't picked up in testing because Jaguar did nearly all their test miles at high speeds and high loads, thinking that that would be the most punishing regime for the engines. The 2.8 passed those tests easily, but the classic failure mode in the early 1970s was an XK6 which had been bumbling around town for a few days (and thus building up a nice layer of lead and soot on the piston crowns) having sudden and catastrophic engine failure as it accelerated down a motorway sliproad for the first time in a while. Hard acceleration got the combustion temperatures up and created the pre-ignition problem. If the hard acceleration was brief enough the engine would survive and the deposits would be burnt off in high-speed/low-load cruising. But prolonged hard acceleration would keep the piston temperatures high enough for long enough for the 'hot spots' to develop and burn out the crown.
I believe the fix was fitting flat-top pistons and altering the ignition advance mechanism for the 2.8s to reduce the advance of the ignition under high vacuum conditions. I suspect it wouldn't be so much of a problem in these days of lead-free petrol, either.
Here's a Series 1 XJ6 I was fortunate enough to drive last year - suitably enough it started life as a 2.8, had two engine failures (one under warranty). When the second 2.8 engine expired the owner paid a Jaguar main dealer to convert it to 4.2, plus the brake/transmission changes from 2.8 to 4.2 so it became, as close as makes any difference, a 'genuine' 4.2 manual o/d.
Lovely, lovely thing, even by the standards of Series 1 XJ6s which are one of my absolute favourite cars.
Absolute 100% accurate explanation of 2.8 piston holing causes. Jaguar released a service bulletin stating to reduce the static ignition timing from 12 degree BTDC to 6 BTDC, Mines one of the last 2.8's built so will have the modified pistons, It's only done 57K miles, The 2.8 really is a sweet XK, Turbine smooth, Shame it lacks a bit in the power and torque department!The problem didn't occure on the 4.2s as they had longer strokes, shorter dwell times and (AIUI) flat-topped pistons. The problem wasn't picked up in testing because Jaguar did nearly all their test miles at high speeds and high loads, thinking that that would be the most punishing regime for the engines. The 2.8 passed those tests easily, but the classic failure mode in the early 1970s was an XK6 which had been bumbling around town for a few days (and thus building up a nice layer of lead and soot on the piston crowns) having sudden and catastrophic engine failure as it accelerated down a motorway sliproad for the first time in a while. Hard acceleration got the combustion temperatures up and created the pre-ignition problem. If the hard acceleration was brief enough the engine would survive and the deposits would be burnt off in high-speed/low-load cruising. But prolonged hard acceleration would keep the piston temperatures high enough for long enough for the 'hot spots' to develop and burn out the crown.
I believe the fix was fitting flat-top pistons and altering the ignition advance mechanism for the 2.8s to reduce the advance of the ignition under high vacuum conditions. I suspect it wouldn't be so much of a problem in these days of lead-free petrol, either.
Here's a Series 1 XJ6 I was fortunate enough to drive last year - suitably enough it started life as a 2.8, had two engine failures (one under warranty). When the second 2.8 engine expired the owner paid a Jaguar main dealer to convert it to 4.2, plus the brake/transmission changes from 2.8 to 4.2 so it became, as close as makes any difference, a 'genuine' 4.2 manual o/d.
Lovely, lovely thing, even by the standards of Series 1 XJ6s which are one of my absolute favourite cars.
The original XJ was Jaguar's high water mark for sure. How long did it take Mercedes to actually build a better luxury car?
They're still so undervalued, and I'd walk past a row of E Types to admire a nice Series 1 XJ6. It was absolutely right from every angle, not an ounce of fat on it. Compare it with the horror show they make now. What were they thinking?
A Regency red XJC for me, c/w chrome steels and the mandatory black vinyl roof. Jaguar's prettiest car IMO.
They're still so undervalued, and I'd walk past a row of E Types to admire a nice Series 1 XJ6. It was absolutely right from every angle, not an ounce of fat on it. Compare it with the horror show they make now. What were they thinking?
A Regency red XJC for me, c/w chrome steels and the mandatory black vinyl roof. Jaguar's prettiest car IMO.
My Dad gave me his 1973 tourqois Blue 2.8 XJS swb, auto as my first car. Lovely car, had a light biscuit? leather interior. Aways amused my mates when I turned up in it, petrol costs were eye watering, £70 to fill the two 11 gallon tanks!!! As I was living at home rent free at the time it wasn't such an issue. Engine let go on the way to Henley after some spirited driving!!! Replaced it with a used 4.2 engine and box, had excellent acceleration due to the wrong rear axle being on it!!! Sadly failed its MOT a few years later and we sold it for scrap as they were worth a few hundred pounds!!!! The inherited my dads 76 4.2 which wasa rust bucket and so badly made by comparison. The swb 2.8 XJS were a very pretty car, perfect proportions!!!
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