XJR-S 6 litre engine + Weber V12 kit for E Type V12 Roadster

[carlv12]

Hello,

my name is Carlos from Valencia, Spain and I am 39 years old. I love Jaguars and hope you can help me:

I have the chance to buy a very fine XJR-S 6 litre with only 40.000
miles and I dream of fitting it with 6 Webers on my 1972 Jaguar E
Type V12 Roadster with 4 speed manual gearbox. I already have
uprated with AJ6 TT Super Sport exhaust, polybushes, Konis etc..

The XJR-S engine has a big parts-availability problem with Zytec etc..
AND: I already have 2 x Jaguat XJ-S V12 and 1 x Jaguar XJ 5.3 C. So
3 fuel injected cars are ok, for the E type I prefer a
more ''racing'' feeling, raw, loud, thirsty...

This XJR-S engine comes without the fuel injection components
and without the distributor, but for a very good price!!!. I
already have the sausage type air filters for the Weber-kit. I hope
that anyone has done this conversion (it does not matter if with
5.3 or 6.0 engine)

Here is Jay Leno's E Type V12 Roadster with WEBERS!!!!

http://www.jaylenosgarage.com/video/vid ... id=1088821

Who has experience or ideas for me concernung this modification. I
live in Valencia, Spain and here nobody has done this before...

I hope you can give me good advices
Thank you and best regards from Spain
Carlos
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[MarkE]

Hi Carlos and welcome.

I?m a huge fan of the XJR-s 6 litre car, and am considering a similar project with my S3?except I like the Zytec setup and injection! I?m down to three XJR-s cars now, but only discovered, as I was having the engine rebuilt on one of them, that the chassis rails were bent on the car. Too late, the engine was built, and the car put back on the road. But it?s the engine from that car that could be my donor for my S3.

I had an engine from an XJS built up for an E type project a couple of years ago, and spoke to a few folks about options. The guy I would suggest to help would be Rob Beere, who has built many such engines, and has a vast experience in racing a S3.

It really depends how far you want to go. The simple option is to bolt on a set of appropriately jetted Webers, but the top end of the V12 isn?t really suited to them in standard form. The 6 litre engine has a superb bottom end, with the TWR long throw crank and the Cosworth pistons?you don?t need to touch that bit. The heads are a bit of a compromise, as Jaguar were trying to squeeze as much ecomomy as they could from the HE engine, and the 6 litre uses identical heads to the standard (HE) XJS.

The heads need to be opened up on both inlet and exhaust side, and a decent set of exhaust manifolds used to better match the webers and improved ports. A racing distributor is required with adjustable dynamic advance, and now the webers can be jetted properly for the 6 litre engine. It will need a day on a dyno to set up properly, otherwise you?ll end up with another weber disaster, with spitting, frothing and flat spots. When set up properly, they are without doubt the best carburettors you can buy?.Ferrari used them for a long time!

The next stage, if you want to go this far, is for fast road cams and bigger valves?but it?s starting to get expensive! It depends what you want?ultimate BHP or more power with even more torque, and the last option is far nicer to drive on the road.

The only bits to swap from your S3 engine are the sump, oil pickup, oil filter housing and front cover / pulleys?.and original exhaust manifolds if you don?t go for the fabricated ones. The wiring all stays the same, but you?ll probably want a new electronic ignition system.

So, bottom line for the 6 litre / weber engine is that it?s not just a carb bolt on job?.the other bits have to match to get anything like the best out of the carbs, and if you don?t do that, you?ll end up with a frustrated and slightly strangled, but good sounding, engine!

Another simple job that will really transform your car is to get the steering rack re-valved, which will give a far more modern, weighted feel to the steering.

One thing to consider carefully is the use of polybushes. I?ve driven an E Type where the owner had just gone through the car changing all rubber bushes to the yellow plastic ones. For sure, the car felt much sharper, but it also felt very harsh, and after a few miles, uncomfortable. He thought that they really transformed the car, which they did because his old rubber parts were worn out. He went back to rubber after only 1000 miles or so, and they felt just as sharp (for road use) as the yellow ones, but he regained that Jaguar comfort and compliance.

Good luck with digging out more information, and keep us up to date with the news. I have a particular interest, but I need to get my S1 on the road and running well before starting any more projects!

[Heuer]

Mark

Are you saying the Webers are a no-no and EFI is the way to go on the V12? I am on thin ice here as I have no real experience of the S3 but I have always thought Webers are only a practical proposition (certainly on the S1) if you are racing or like the smell of petrol! I know Harry and you are really into the V12 engines so your thoughts will be of great value. Anyone else have a view? Want to dive in Harry?

[MarkE]

David, for me, a well sorted Jag V12 on webers would be the ultimate configuration. It?s not better than the injection solution, and in many respects it?s a darned sight worse. But it provides the raw, 60s V12 feel and sound that make the injection version seem a little tame.

A couple of things prevent me from going down the weber route. Firstly the cost to do properly is somewhere around ?10k, assuming getting a pro to do the work (and providing a good engine as the base). Secondly, the running cost, at 5mpg, would make popping down the shops a wallet denting experience. Realistically, you?d need to install a much larger fuel tank, as the range with the standard one would be somewhere in the region of 50 miles.

Lastly, and this is the one that hasn?t been cracked yet, is that under some circumstances, the webers can play up. The E Type engine bay is a very hot place, and the webers nestle in-between the V, the hottest place. With the shortest ram pipes fitted, they only just fit under the bonnet with fairly crude gauze filters. It?s essential to get cold air to the intakes, otherwise they really play up, so running a couple of 4 inch pipes under the bonnet to the nose is a must. This sorts it out for normal running, but in slow traffic, on a hot day, the webers can play up with lots of ?spitting back? through the air intake. That means flames, and potentially a scorched under-bonnet.

So even at best, there are compromises and times when the car would best be left at home. But the sound of a 6 litre on webers has to be one of the best sounds of any car!

[Heuer]

Secondly, the running cost, at 5mpg, would make popping down the shops a wallet denting experience. Realistically, you?d need to install a much larger fuel tank, as the range with the standard one would be somewhere in the region of 50 miles.

[carlv12]

Hello,

first of all I want to thank you all for the quick answers. I am an absolute Jaguar lover and before starting this idea I have interchanged opinions with Roger Bywater from AJ6, Rob Beere, Steven Mofatt and other experts in Germany. The basic conclusion is: EFI is smooth and near optimum, Webers are raw, loud and have hot spots etc. BUT:

I love coversions that do NOT affect the outer look or almost not, so for example my both XJ-S V12 have Dayton wire wheels, but DISHED with 7x15 and 7x16 on 235/60 R15 and 225/55 R16 and it looks fantastic. But alloy wheels are technically much better, lighter, no vibrations, easy to clean etc.. but the look and the feeling of wire wheels for me is great. If I want a perfect running car I buy a Nissan... you know what I mean.

But I want a cat with his own soul, his problems etc.

Having tha chance to buy a 40.000 miles 6 litre engine from XJR-S but without the faulty Zytec system I always liked the look and sound of Webers. I already have the sausage type air cleaners that are difficult to find. And air induction on XJ-S is also a problem because ot the heat. But at stop-and-go you never need 300 hp and when driving there are solutions like air ducts or similar even for the E Type.

Fuel consumption is not the problem for me, because I drive only 800-1000 miles/year.
Having already 3 smooth EFI Jaguars the Weber conversion is for me a challange, even more together with a 6 litre engine!!!!

My E Type is not at all normal, I have the 3.07 diff (3.54 is awful), the Rob Beere adjustable power steering kit, Konis (will change to coilover AVO that are adjustable from the outside), HBE anti roll bar front and REAR, stiffer torsion bars, AJ6 TT Super Sport exhaust (what a sound!!!), Rossini brake discs with green stuff pads (yes, the really ave less brake dust), wooden steering wheel, and much more things changed.

So I prefer the raw, loud, harsh feeling of the Webers and it is secondary if I get 300, 330 or 350 hp, it is always more then enough for me and my "old" car. To convert to EFi alsdo need a good donor engine and a lot og electrical parts like wirings, ECU etc.. or you buy a complete donor car...

I hope we can discuss much more about this...
Regards
Carlos

[MarkE]

A chum of mine built a XJ Coupe V12 race car a few years ago, with a TWR 6litre engine as the base, and running webers. He found that in a race it used fuel in equal measure to distance....1mile...1 gallon. It didn't half go though!

[Heuer]

Carlos sent me these pictures of his cars - fantastic collection and clearly no concern for fuel consumption!

[MarkE]

Carlos must be a fully paid up member of Greenpeace, as am I.

Just a quick note on the Zytec, Carlos. The system employed on the 6 litre XJR-s is no more troublesome than the standard 5.3 systems, in it?s different guises. The ECU is bullet proof, but like any ECUs of the era, it can be damaged with power spikes?usually caused by some ham-fisted dumb owner trying to improve things!

The biggest issue with the system is the Lucas connections, especially at the resistor packs that sit just behind the headlamp and cold start sensor at the front of the engine. The standard XJS has one resistor pack, and the 6 litre has two, with the lousiest pin connectors you can imagine. This area of the car gets damp, and the pin connectors fail, leading to the engine misfiring and feeling like it has run out of petrol. Many Jag ?experts? misinterpret this as a distributor or ECU problem, and quite a few cars have been scrapped because of this.

I found this out early on in the ownership of an XJR-s, as my first car failed. It took 30 minutes to clean up the connectors, and a few others that lurk around the front of the car, and it?s run perfectly since.

If all else fails, the standard 5.3 ECU, distributor and resistor packs can be substituted with very little impact on performance. Better still, the last V12s made were all 6 litre, and their electrical bits can also be substituted with no impact.

Right now, there is a huge slump in the prices of V12 XJS and XJ12 cars of all sorts. They are usually rusty with loads of other problems?but nearly always, they have perfect engines. It?s very hard to ruin a V12. Tatty XJR-s 6 litres can be bought for ?1000, and the last-of-the-line 6 litre XJs for even less. It?s a good time to stock up if you have the space. I?m sure we?ll look back in 10 years time wishing we had!!

[carlv12]

Hello,

I have ordered the Weber kit and alreay bought the XJR-S engine!!!!!

Then converting my 4 speed manual E Type V12 to the 6 litre XJR-S engine + Webers, I must consider the following modification points, right?

1) the oil sump from E Type or even more modifications?
2) water pump from XJR-S or E Type?
3) oil filter from XJR-S?
4) spark plugs from XJR-S or E Type?
5) a high pressure recirculating fuel pump or the regular E Type one (part number or which one to buy?)
6) modifications to the bellhousing attchments?

Thank you and best regards from Valencia.
Carlos

[carlv12]

Hello again,

finally I cannot use the 6 litre XJR-S engine, due to internal engine problems. I am rebuilding my original 5.3 E Type V12 engine using new pistons + liners, valves, water pump, studs, etc.

Now I need your expert-advice:
I already have the 6 carb. Weber kit (WITH choke) + the sausage type air filters and know that I must reduce the engine height (engine mounts), I must reduce engine heat to the carbs, use a recirculating pump to avoid fuel inside the carbs when hot and isolating shims etc.

My mechanic thinks that the linkage will be a problem, that accelerating will be hursher. What can we do to get the smoothest possible paccelerator pedal feeling. I understand that the Weber's are not a EFI, but I just do not want to have only a rece car that is impossible to drive in the city. I can live with a hursher response, but not radical.
I thank you for all ideas, but please don't tell me NOT to fit the Weber's...

Regards from Valencia
Carlos

[PeterCrespin]

Hello again,

I already have the 6 carb. Weber kit (WITH choke) + the sausage type air filters and know that I must reduce the engine height (engine mounts), I must reduce engine heat to the carbs, use a recirculating pump to avoid fuel inside the carbs when hot and isolating shims etc.

My mechanic thinks that the linkage will be a problem, that accelerating will be hursher. What can we do to get the smoothest possible paccelerator pedal feeling.

The linkage is just a mechanical thing - no mystery and you can do it any way you like that gives you the travel and mechanical advantage you want for either quick-action or slower action opening. Surely the kit came with some linkage parts to get you started? If not, they are available from SC Parts amongst others.

As for clearance, every millimetre counts - especially at the front edge of the front carbs. Good airflow conventionally requires the nearest surface opposite a ram pipe opening to be no closer than 1.5 times the diameter of the tract. Obviously this is totally out of the question unless you get a horrible bonnet scoop. I only mention it to show you how bad the situation is and therefore to encourage you to take every possible step to get the situation as 'least bad' as possible and add every available millimetre to this gap.

As well as dropping the engine a fraction, you can shim the bonnet up a fraction. The more you raise it the more out of line the lower side edges will be along the sills and the more wedge-shaped the vertical panel gap will be on each side at the back of the bonnet. However, it is worth at the very least shimming to the maximum possible to get clearance with panel gaps you can accept. If it were my car I would consider shimming as much as maybe 10-15 mm vertically with longer bolts and opening up the hinge holes as required, then doing any necessary body work to the back of the bonnet to sort out the panel gaps. You would hardly notice this extra height on the car. If you did, you could split the difference by dropping the front suspension maybe 5mm?

This all seems a lot of work, but remember if you only have 10 mm clearance at the front carb (maybe less) it is a 100+% increase over what you had.

As for cool air, the solution to this will spoil some of the aesthetic appeal of the Webers. You need to put an alloy or maybe stainless or carbon fibre sheet over the whole vee, between the carb throats and the bellmouths, to keep the heat away from the engine intakes. You could insulate the lower invisible surface even. Then feed the space above that sheet with cold air, via existing or new trunking from above and in front of the radiator. I'd also arrange a feed into the front of the vee, especially if you have air conditioning, to keep heat under control there. Obviously the ignition amp, if present, would be best moved to the picture frame.

If you curl the edges of the new bottom plate upwards and put a rubber edge seal around the shaped perimeter, you can make a wide flat semi-sealed 'air plenum' using the skin of the bonnet as the top surface. Provided you fed lots of cold air into this narrow flat 'box' you could minimise the heat intake issues. I wouldn't bother trying for a 'raim air' effect, just get lots of cool stuff in there.

But really, you are trying to make the best of a bad job and there isn't room to do the job right. Still, if your objective is a snarling spitting V12 with 'soul' then you should be OK :-)

[PeterCrespin]

Forgot to mention...sticking with the 5.3 is good news for your manual transmission plan.

The 5.3 uses the standard V12 bell housing, whereas the 6.0L had a different bolt pattern to suit the GM 4L80E auto box. As it happens, the old bosses are still present on the 6.0L but are undrilled. Still, it's easier to get a manual on the back of your 5.3 than a 6.0L so that aspect at least will be simpler now. Enjoy the car.

[Woolfi]

I have done a conversion to a 6,0 motor in my EV12. The motor is working great and has much more power than the 5,3.
O sunday we had a sunny warm day and I have done a acceleration-contest with a 400 hp Maserati Quattroporte of a friend. We started with 50 mph and stopped at 100 mph. For my big surprise the Maserati was not quicker than my EV12. The car accelerated side by side and the Maserati was not able to pass my car. The wight of the Maserati is roundabout 1850 kg without driver. I calculated, that my EV12 with 6,0 L motor and 4 Strombergs must have roundabout 320 horsepower compared with the Maserati.
This is not a typical hunters fairy tale. For a simple conversion with 4 strombergs the car is running great.
Kind regards Wolfgang Gatza

[carlv12]

Hello experts,

what do you usually do with the oil breather when fitting the 6 Weber's? Is it possible to fit a conduct to an external oil deposit? Because it's impossible to fit it into the air filters, because the oil will destroy the foam of the air filters.

Thank you and best regards from Valencia

Carlos

[Heuer]

Carlos

One my S1 with an ITG fiter I vent to the ground although you could make up a catcher tank if you have an environment conscience.