RE: Jaguar XJ-S V12 | The Brave Pill
Discussion
Touring442 said:
The AJ6 was certainly a tough and reliable unit. They were capable of 200'000 miles and apart from the odd head gasket they had no real weak points as long as it was maintained. The old XK wouldn't do that and I doubt many V12's did either. Imagine the fuel cost!
The XK was ready for a rebuild at 100k, I've not heard of anyone actually wearing out a V12 though!stickleback123 said:
The XK was ready for a rebuild at 100k, I've not heard of anyone actually wearing out a V12 though!
I have 185k miles on my 94 6L V12. Here in the US, I find it very hard to find any 5.3's with over 100k miles. Likely because of the valves dropping from overheating.Touring442 said:
The AJ6 was certainly a tough and reliable unit. They were capable of 200'000 miles and apart from the odd head gasket they had no real weak points as long as it was maintained. The old XK wouldn't do that and I doubt many V12's did either. Imagine the fuel cost!
Had a head gasket go on my AJ6 XJS around 2,500 miles ago (its on over 197,000 miles now), and generally a great engine. Just had the injectors rebuilt too just to see if it made any difference. I've got a 6.5l V12 XJS (which was originally a 3.6) that has over 224,000 miles on the clock, but I'd have to check how many of those miles are the V12 ones.
stickleback123 said:
No offence intended by this, but only someone who has had no experience of the way a V12 delivers it's power would suggest a 6 pot of equivalent output as a replacement. While you could doubtless match the power output of the V12 very easily with a more modern I6 there is so, so much more to it than the headline figures
No offence taken! I have experience with most engine configurations, including V12's. Yes, they are lovely smooth things, but that wasn't my point. I was just imagining a more modern powerplant to give the car some more go. A well tuned 6 does follow with Jaguar designs. R400TVR said:
I was just imagining a more modern powerplant to give the car some more go. A well tuned 6 does follow with Jaguar designs.
People have been dropping Chevy v8s into jaguars for as long as jaguar v12s have been dropping valves. A good quality LS conversion looks like it was designed for the car. Service items are easy to get to and the engine sits further back which is said to improve balance
R400TVR said:
That looks nice! In an XJ saloon, the V8 would suit, but i don't think that the XJ-S is a V8 car. I know it's just me, but I reckon a six is still the best.
It’s weird isn’t it. That installation looks lovely and it almost certainly makes for a great car but even though they originally had thoughts of fitting the Rober V8 it just doesn’t feel right. alabbasi said:
R400TVR said:
I was just imagining a more modern powerplant to give the car some more go. A well tuned 6 does follow with Jaguar designs.
People have been dropping Chevy v8s into jaguars for as long as jaguar v12s have been dropping valves. A good quality LS conversion looks like it was designed for the car. Service items are easy to get to and the engine sits further back which is said to improve balance
[Img]http://www.jaguarspecialties.com/photos/LS1-2.jpg[/thumb]
R400TVR said:
That looks nice! In an XJ saloon, the V8 would suit, but i don't think that the XJ-S is a V8 car. I know it's just me, but I reckon a six is still the best.
Not as smooth for sure but it gives it the performance it should have had and costs next to zero to fix. More importantly, it's kept a bunch of otherwise nice cars from being dismantledalabbasi said:
Not as smooth for sure but it gives it the performance it should have had and costs next to zero to fix. More importantly, it's kept a bunch of otherwise nice cars from being dismantled
Unless you are on the Pistonheads side of the pond (UK/Europe), where a Chevy V8 is usually much dearer and rarer than a Jag V12. Hence why this conversion is pretty much non-existent.Olivera said:
alabbasi said:
Not as smooth for sure but it gives it the performance it should have had and costs next to zero to fix. More importantly, it's kept a bunch of otherwise nice cars from being dismantled
Unless you are on the Pistonheads side of the pond (UK/Europe), where a Chevy V8 is usually much dearer and rarer than a Jag V12. Hence why this conversion is pretty much non-existent.stickleback123 said:
Olivera said:
alabbasi said:
Not as smooth for sure but it gives it the performance it should have had and costs next to zero to fix. More importantly, it's kept a bunch of otherwise nice cars from being dismantled
Unless you are on the Pistonheads side of the pond (UK/Europe), where a Chevy V8 is usually much dearer and rarer than a Jag V12. Hence why this conversion is pretty much non-existent.In the US they have "cheap" gas, i.e. lower octane such as 87 or 85. Which is probably more akin to 2 Star petrol or maybe lower. Certainly way lower octane than we get here. Even more so as different octane ratings are used in the UK and USA too.
In the US they also cover a lot more long and extreme distances simply due to the size of the country and population density.
And I suspect there is a degree of higher abuse from non car enthusiasts. Most American built cars are very durable and simply don't need TLC to keep them running sweet. the V12 Jag probably liked a gentler touch by and large.
alabbasi said:
R400TVR said:
That looks nice! In an XJ saloon, the V8 would suit, but i don't think that the XJ-S is a V8 car. I know it's just me, but I reckon a six is still the best.
Not as smooth for sure but it gives it the performance it should have had and costs next to zero to fix. More importantly, it's kept a bunch of otherwise nice cars from being dismantled300bhp/ton said:
I suspect there are other mitigating reasons.
In the US they have "cheap" gas, i.e. lower octane such as 87 or 85. Which is probably more akin to 2 Star petrol or maybe lower. Certainly way lower octane than we get here. Even more so as different octane ratings are used in the UK and USA too.
In the US they also cover a lot more long and extreme distances simply due to the size of the country and population density.
And I suspect there is a degree of higher abuse from non car enthusiasts. Most American built cars are very durable and simply don't need TLC to keep them running sweet. the V12 Jag probably liked a gentler touch by and large.
None of this is true. In the US they have "cheap" gas, i.e. lower octane such as 87 or 85. Which is probably more akin to 2 Star petrol or maybe lower. Certainly way lower octane than we get here. Even more so as different octane ratings are used in the UK and USA too.
In the US they also cover a lot more long and extreme distances simply due to the size of the country and population density.
And I suspect there is a degree of higher abuse from non car enthusiasts. Most American built cars are very durable and simply don't need TLC to keep them running sweet. the V12 Jag probably liked a gentler touch by and large.
Octane levels in the US vs UK is about the same. The ratings are different.
The average mileage for most cars is 12000/year which is about the same as the UK, this does not make a difference as the V12 typically fails within 50k miles. There are plenty of car enthusiasts in the US, as represented by most car forums which are dominated by US members
I think that heat is a big factor, also the fact that cars will more likely rust away in the UK before the engines fail, vs the US where many of these cars are still rust free. The other factor is labor costs. Jaguar specialists charge $125/hr or more and most XJ's cost under $10k. It's hard to justify the cost of long labor hours needed to maintain these cars when an LS engine / 4 speed swap will cost considerably less.
There are a couple of very good conversion kits available, the engines are readily available here in the US and once swapped, you have a drive train that's capable of 300+hp (or much more) with super cheap servicing costs and the ability to get 30+mpg when installed with a 4 speed overdrive transmission.
I currently own 3 V12 Jags and a 6 cylinder. While I'm enthusiastic about the V12. I'm also a pragmatist. After reading some of the posts here. I'm wondering how many who posted have actually owned a V12 Jaguar.
Edited by alabbasi on Tuesday 17th September 23:57
DonkeyApple said:
An LS3 with a soft cam and a high quality management system can be a very smooth engine. I’d wager maybe even smoother than the average person could tune the carbs on an old V12.
Smooth, sure. Not V12 smooth. I know a couple of people who converted to an LS engine using the GM ECU. They said it was super simple as the ECU is pretty much self contained and did not require an aftermarket controller.Edited by alabbasi on Tuesday 17th September 23:59
alabbasi said:
None of this is true.
But it is 
alabbasi said:
Octane levels in the US vs UK is about the same. The ratings are different.
Yes I mentioned this. But in the UK the lowest grade is 95 RON which is about equal to 91 octane in the USA. We also have 97, 98 and 99 RON at the pump. Which are going to be more equal to 93 thru 95 octane ratings in the USA.But you guys also get lower grades such as 87 or 86 octane depending on State. This would be equivalent to something like 91 RON here. And we have no such thing.
It really isn't inconceivable that in the USA, some V12 owners have used this lower fuel grade, which in turn could be a contributing factor to why you see failures that aren't generally seen in the UK or Europe with the same engine.
alabbasi said:
The average mileage for most cars is 12000/year which is about the same as the UK/quote]
It might be similar, but in the UK most people doing high miles won't be doing it in a big engine vehicle. But in the USA it is more common. I suspect if you compare cars such as the XJS from the USA with those in the UK, as a trend the US cars are likely to have covered greater distances.
It might be similar, but in the UK most people doing high miles won't be doing it in a big engine vehicle. But in the USA it is more common. I suspect if you compare cars such as the XJS from the USA with those in the UK, as a trend the US cars are likely to have covered greater distances.
alabbasi said:
There are plenty of car enthusiasts in the US
Never said there wasn't. But by the numbers there are also a great many non enthusiasts too. People who just expect a car to work.alabbasi said:
I think that heat is a big factor
It might be, some parts of the US are hot. But not all parts. And some parts of Europe are also hot too. It is something to consider, but it isn't a unique factor only for the US climate.alabbasi said:
The other factor is labor costs. Jaguar specialists charge $125/hr or more and most XJ's cost under $10k.
The same is true in the UK, only in £ not $. I don't see how it is a factor.alabbasi said:
I'm wondering how many who posted have actually owned a V12 Jaguar.
1982 XJ-S HE. And my dad had a 1993 6.0 XJ. Apart from a couple of burst water hoses on the XJ-S not a single engine issue at all. In fact both cars were very reliable all things considered. And both owned for a good number of years. I was also a member of a couple of Jaguar owners groups/clubs back in the day. And burnt valves on a V12 is a new one on me.alabbasi said:
300bhp/ton said:
burnt valves on a V12 is a new one on me.
Valve seats dropping on these engines is common knowledge even if you don't know about it. I'm sure that if you ask around, somebody more knowledgeable will tell you about it. Its like the issues you guys get with the Rover V8 too. Apparently in the USA they are known for blowing head gaskets. But it just isn't a thing here. Oil leaks, worn cam/followers, dodgy EFI and an occasional slipped liner. But not head gaskets.
Was watching the TFL Truck last night on YouTube. One of the presenters has bought a 4.6 D2 and constantly moans about it running hot and HG issues. Interestingly when they were doing an mpg test vs a Suzuki and a Jeep. They note he runs it on 86 octane fuel, to which his son & co-presenter notes it should be run on premium.
Of course this is only circumstantial evidence and not indicative proof. But it is interesting non the less. In the UK as we don't get this grade of fuel it is 100% impossible to put vehicles in the same conditions.
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