Here Kitty, Kitty 

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Background San Diego, 2003.   Those of you who know me know I really, really, really like cars.  More than that, I like cars with personality, panache, and especially performance.  If I were independently wealthy I'd have a collection to rival Leno's and Custler's.  Since I'm not, my collection has had to come one at a time.  Over the years I've had some neat machines starting with a '52 Chevy Sport Coupe with a Jimmy 270 engine in High School, (and not counting the 4-wheelers that are fodder for another feature sometime) I've had two Austin-Healeys, two Porsches, a '65 '289' Mustang, a '63 Thunderbird, a Fiat 1800 Spyder, a BMW L7, and most recently the Jaguar Series III Vanden Plas (below, named "Bagheera") which I've had now for several years since it starred in the children's movie I produced called Moosie..

Series III Van Den PlasEach of those vehicles was special in its own way.  The Healeys (especially a Bug-Eye Sprite I raced in H-Production in my college years)  have the nod for the ultimate in pure unadulterated fun rides; the Porsches were high powered slot cars that handled like nothing else I've ever driven; and the BMW was probably the best engineered car I've ever been around.  But of them all, the Jaguar quickly became my overall favorite: sleek, classy, the look of luxury with the feel of a typical English sports car that handled like silk.  

And, despite all of the negative stuff you always hear about Jaguar reliability, growler this car has been very stable.  It did, unfortunately, come with a small problem:  the rear seal  dripped oil directly onto the tail pipe.  The engine itself didn't burn any oil and actually seems to run fine, but the hot oil dripping from the seal on to the tailpipe smoked like Holmes puffing on his beloved Meerschaum.  At a stop sign it is mildly embarrassing as the smoke billows out from under the car and nearby drivers ask if I'm on fire while neighbors come running with their fire extinguishers. 

But on the highway the sleek black cat was in its element.  Strong, highly controlled, and a sedan--oops, that's "saloon" to you folks in the UK--faster than any law outside the autobahn and Montana, the Jag is a dream to drive.  Besides, it was English so of COURSE it leaked oil.  They say the reason the English don't make watches is they couldn't stand the oil dripping down their wrists.  Others insisted that a "JAG-you-are" does NOT leak oil, it is, like other cats, merely marking its territory.  And mine was marking a LOT of territory!

But alas, the leak had taken a turn for the worse,  probably from the long runs to Palomar College and now to Mira Costa College from San Diego.  Something was going to have to be done.

Options Well, the available options were not wonderful.   Despite being what I think is the best looking sedan Jaguar ever built, it's depreciation finally had hit bottom with a common value at an amount considerably less than the cost of rebuilding the engine. The good news was that the value is now slowly on the rise, but the bad news is that it will not be overnight.  And I need the car repaired before it ends up really blowing itself up or getting me stopped by the EPA.  However, most importantly, I need something reliable for the long miles I spend on the road.

Alan Curtis, the owner of Exclusive Jaguar in San Diego, is simply incredible.  He runs a great, reliable service shop, and besides being an incredible artist with Jaguar service, is something even more extraordinary: a scrupulously honest mechanic.  Although he was a dealer's service manager before opening his own shop, he is a racer and performance enthusiast without the purist's attitude.  I couldn't possibly recommend him or his shop highly enough to express how I feel about it without making it sound like he must be a member of the family. 

He has both a great sense of humor (in that bitingly satirical Brit fashion) and is endlessly patient. And to cap it all off, he's a performance guy with a background in racing.  He had to be patient in order to tolerate the pestering I gave him in my search for finding a solution. After listing to my wants, he provided me with a number of options.  (1) rebuild the Jaguar engine in the Vanden Plas,  (2) replace that engine with a Chevy 305 or 350 V8, (which are common replacement for Jag engines).  

Oh man!  ALL of those options cost significantly more than the value of the car, even after the work. Bummer.  And as it sat, in its plume of smoke, it had virtually NO value to a buyer other than a parts yard.  This was not going well and not helped by a personal treasury supported only by part-time teaching.  

While trying to figure out what to do I was just wandering through his lot when I saw it...Sitting gathering dust and street grime amongst other vehicles on his lot was something that caught my eye: a Jaguar of a type I'd not seen before, only read about. It was an XJ-SC Cabriolet.  A fairly rare and, to me, beautiful, version of the XJ-S model with a Targa-styled top.   Actually,  the XJ-S has been the most produced and sold sports car in Jaguar history---more of a Grand Tourer than pure sports car--- with over 100,000 sold.  But there were only 5,014 XJ-SCs  produced between 1983 and 1988 (according to John Bleasdale who keeps the Cabriolet Registry) and of those, well under 2000 were imported to the US. That makes it a somewhat uncommon car.  

So what does that have to do with me?  Well, this car's V12 engine was blown with a cracked head.  However, its owner was in dire straits and could not afford to have it fixed.  Worse (for him), he really REALLY needed to sell the body and would let it go for a ridiculously low amount.  I couldn't buy a well used Yugo for that amount.  Oh man... I loved it!  But it needed an engine. I wasn't keen on the cool image of pushing it around the highway. 

Then, after some searching, Alan came across a '95 300+ hp LT1 350 cid (5.7 liter) GM engine with matching 4L60E transmission at a good cost.  Seems some kid trashed his hot  muscle car which had far more power than his driving skill could handle; a pretty common deal in this area.    

In total, and counting labor, they were within spitting distance of the cost to rebuild my sedan.  Well... c'mon now, this is just too much for an old performance car nut.  So I told him to go for it.  The finished car would be far less than I would have to pay for a mediocre car with zero personality and no performance.   So, in October of 2001, I told him to go for it.  

Assembly The deal was, he could work on it on his own time and not take time away from other "paying" customers and for that I would get a heck of a good deal on the labor.  So the Engine was ordered in and soon the broken V12 was out and the hot LT1 was hanging from a cradle and being fitted into the waiting body. 

Alan set about custom fabricating and fitting all of the parts needed for the conversion.  One small problem turned into a boon for us.  The engine fit like a glove which was a problem for the exhaust system.  This engine was the dual exhaust version of the LT1 and there was not sufficient room to slip the exhaust manifolds down alongside the engine without some creative sheet metal work which we did not want to do if at all possible.   So, after several options were tried, none of which fit quite right or, if they fit, looked quite right,  a set of new Corvette "rams horn" manifolds were tried.  They not only fit, they resulted in a small but unexpected horsepower gain.    

But this important breathing system was even more improvedXJSC Tail Pipe by the fabrication of a totally new "aluminized" exhaust system running through hi-flow cats and twin Flowmaster Series 50 mufflers, then out through the rear suspension (instead of the original pipe's convoluted bends required to go up and over then back down for the tail pieces) that was clean with very little bending and all of that at less than 45 degree angles.  The shot to the right shows it passing through the rear suspension and half-shafts and is looking forward from the left-rear of the car.  


Of course, this ability to get rid of air was now so well done that it was only reasonable to think about getting more air into it which would, of course, up the power.  But more about that later...

So, the work progressed and it was pretty frustrating to see it just sitting there.  I could hardly wait to get it on the road and bugged Alan constantly with the mantra, "So, can we fire it up and take it for a spin?".  This would have been a GREAT car in the mountains in Colorado. 

The goal was to create an installation that was as good or better than the factory would have done it.  It was not to look like a chop shop special or a plumber's nightmare. In fact the goal was that if a viewer did not know what they were looking at, it would look like an engine installed at the factory.   And Alan accomplished that beyond my wildest expectations.  A good example is the completely customized SPAL dual electric fan setup in the picture above on the right (taken during phase one).  The entire mounting shroud is fabricated out of sheet aluminum and designed to force incoming air from the front grills through the radiator and when speed diminishes to use these two fans to draw it in. 

Next, below, is a photo of the engine in basic "Phase 1" configuration  for the preliminary testing period. (You are looking into the engine bay from the driver's side (left side here in the colonies.)  The engine, which is nearly 300 lbs lighter than the Jaguar V12, also sits lower and farther back.  (This allowed the radiator to also be moved to the rear about two inches and still leave room in front of the engine for access.) The result is both improved power to weight figures (the original power to weight (HP to lbs) ratio is .07:1and the finished one is .13:1) and also better weight distribution for more neutral steering.

Now I confess I lobbied Alan hard to just go ahead and put it all together in finished form but he refused, saying we needed to test the basic engine first to make sure it was all OK and up to snuff before he added the supercharger for phase 2.  I knew he was right but it was frustrating to see the Vortech sitting off to the side and NOT in my engine bay.

Supercharger?  Did he say, "Supercharger?"  Hang on, we'll get to that...


Finally in mid-April of 2002, nearly six months after the go-ahead was given, the car is in my hands for its preliminary tests. And a beauty it is! 

Because it is a swapped engine, it had to go before an emissions "referee" here in The People's Republic of California before it could be properly licensed.  So the plan was to drive  it a couple of weeks to work out any bugs then get it smogged.  Sure sounded easy...  Ha!


Emissions Idiocy Well we ARE in Kalif... uh... California.  Here there are a set of arcane rules about engine conversions that rival the tax code for inexplicable complexity with minimal, if any, gain.  The engine must be the same or newer age than the body and it must have all of the restrictive stuff on it applicable to the engine's vintage.  We were off to a good start then by putting the 1995 engine in the 1988 body.  But there was a small twist we did not expect.  The federal emissions specifications prior to 95 were "OBD I" and were originally supposed to be replaced by new standards ("OBD II") in 1995.  But it didn't happen uniformly with all models and engines.  For GM cars, as an example, 40% of GM engines were changed leaving 60%, including the LT1 (which went in the hottest versions of the Corvette and F-Body cars) which remained OBD1 until 1996 when the conversions were completed.

However this bit of information has not made it into the California smog referee's database.  It says ALL 1995 cars were OBD II and need the new 16-pin connectors of that spec.  This is not a problem for normal cars since they were approved at the factory and in their original bodies are only tail-pipe tested.  But with the swap, the referee looked in their database for the needed stuff, compared it to my car... and promptly failed it.  No amount of discussion would convince him.  So, another trip through the line at the DMV produced another extension on the temporary permit and we made arrangements with a local Chevy dealer to inspect the engine and document that it was properly set-up for its vintage.  Didn't matter to California...the computer said otherwise.

So, of course that didn't work either.  I was prepared to lie about it but the first referee already had me in the database as a 95.  I tried to explain the situation to him and to his credit he agreed to call and look through other books. While he was doing that two auto instructors from Southwestern college came over to look at the engine and were there when he returned.  He said to me, Nope, it is an OBD II.  And in unison the instructors said, "No it's not, its an OBD I."  He was dumbstruck as the instructors explained, almost verbatim, what I had just told him.  So what did he do?  Did he have the data corrected?  He did not.  He typed in numbers for a 94 and it accepted the plug and passed.  hopefully for future emissions checks all will be well since it will now read on the State computer as data that will be accepted.  What a crock of ...  oops, I can't say that on a family show.


Supercharger Finally... FINALLY the car was ready for the final touch, a Vortech V1-S supercharger.  Intake systemThe engine was pre-planned for this installation and already had a custom cold-air ram intake system in place with high volume K&N-type filter and a space left along side the engine.  This particular centrifugal supercharger was chosen because I did not want to add a scoop to the hood and destroy the lines of the car or give away it's "secret" so blatantly.  Below you can see it nestled under the intake plumbing down alongside the engine.  

VortechCentrifugal blowers are not the most efficient, I admit, but certainly it was acceptable for this installation and my road needs.  Much more boost and the engine would be under constant strain with reduced reliability, a negative to me even with more power.  Another 134 HP on top of the now existing 330-335 HP was surely more than enough to propel me down the road as I wanted. If this were Europe where high sped driving was more common and emissions restrictions less onerous it might be different.  But even so, this will smoke tires easily and rapidly exceed speeds where the car is aerodynamically stable and, in any case, it is quite competent to go well above the normal XJ-S's top speed of around 150-160.  How good is good enough?

Crane Hr6 moduleOf course nothing is as simple as it seems.  The increased air volume/density needed more fuel and then more spark to ignite it. Ignition was supplied with a new CraneCams multi spark ignition system including Hi6R module, hot coil, and dash mounted retard switch. The engine bay was starting to get crowded again so the module was mounted to the fan shroud above the fans at the front of the engine.

Fuel regulatorsThe fuel problem was solved with a secondary fuel pressure regulator that would supply the additional fuel when needed as boost rose at higher RPMs. Normally this is mounted to the valve covers but that looked a bit clunky so Alan made a mount to attach it to the back of the engine bay on the firewall.  That got it out of the way and left better access to other components as well.

Of course all that power ought to look good in the bay too.  engine bay after blowerIn addition to being a factory quality install, I also wanted the engine bay to sparkle and be as eye catching as the rest of the car.  I did not want it to be ostentatious and tacky, but I did want it to be pretty to look at.  Due to my old hot-rodder days that meant some chrome and/or polished surfaces.  Not a lot--not every nook and cranny--but some of the shiny stuff to reflect light and highlights.  

I know I tend to anthropomorphize my cars; naming them and such to, as my uncle used to say, build good medicine with your tools.  But with that comes the sense that when a car looks good and is clean and cared for it is happier and runs better.  Its metal heart beats stronger in a flashy, clean suit.  "Nonsense," you say?  Yeah, well, ask any hot-rodder or racer or just plain car nut.  They'll tell you it's true...

For some larger and more detailed pictures of the engine, CLICK HERE.


Specifications So what manner of beast do we have here?  Well, here are the general specs on the finished car...


  • 1988 Jaguar XJ-SC Cabriolet (Cabriolet build # 3409)
    (I have both the hard and soft rear "half" tops for it) 
  • Color: "Silver Birch" (sort of a metallic "champagne" color).
    Tops are both a chocolate brown.  Interior is  "Biscuit."
  • Road Wheels are American Racing 3-piece Alloy
  • Tires are Dunlop Sport 5000 225/60-15 "V" rated.
  • Weight as finished: (half-full fuel tank, spare, no passengers or cargo, with hard rear top fitted and panels in place it weighs in at approximately 3,675 lbs.


  • 1995 GM LT1 350 CID (5.7 Liter) w/ aluminum heads.
  • Custom rammed-air cold air intake with K&N high-flow filter. 
  • Vortech V1 Supercharger.
  • Corvette  "rams horn" manifold
  • Crane Hi6R multispark ignition, coil, retard switch 
  • Twin Flowmaster Series 50 mufflers, high-flow cats, and custom 2.25" aluminized exhaust plumbing.
  • Cooling:  SPAL twin high performance 11" electric fans,  Modified Jaguar V12 radiator with relocated ports set back 2 inches..


  • GM 4L-60E 4-Speed Automatic with Torque Converter.   
    Final ratio is 0.73:1


  • Jaguar stock,  2.88:1 final drive

(For more detailed pictures Click Here)

The result of all this is an extremely elegant car that handles like a dream thanks to a far better weight distribution and with at least 450 bhp that redlines at around 6,000 rpm but only reads 1,750 rpm at 70 mph in high gear (2050 @ 80 mph and 2700 @ 100 mph).  


       XJ-SC Poster
Photo by David King, taken at Clark's Lake, Anza-Borrego, California


So, how fast is it? Well, there's the math and then the clock.  Let's do the math first.

Actually, the math is complicated and requires knowledge not only of the available horsepower at various (and higher) RPMs but also of the car's coefficient of drag, the frontal area, the tires' diameter, and the tranny and rear end gearing, etc. to determine what the gearing allows and then whether or not there is sufficient power to overcome the nearly exponentially increasing wind resistance at elevated speeds.  That's what computers are for and the result is a calculated potential speed of 197 mph at 5300 RPM  though there is nearly another 1000 RPM before my arbitrary redline. It will require about 438 HP to do that, which it has. However, it takes more than the 450-475 HP it has available in order to hit 215. Discounting the issue of stability it should easily knock on the door of 200mph.

 So it is clearly not enough for serious racing where speeds routinely top 200 by wide margins these days.  But it's not likely to have to impede the flow of traffic anywhere but Le Mans.

A fellow member of the Jag-Lovers web site has a gorgeous blown XJ-S V12 with around 700 HP which should dust me off easily.  But you can see him coming with a large hood scoop that, to me, both gives away the secret and breaks up the lines of the car.  And, in any case, this is far more than I thought was needed or was practical for the daily commute or most road trips anywhere short of the autobahn.  It is also far from the stealth fighter I wanted for myself (though I confess I'd love to drive his to see what it felt like in comparison).  And, if I decide to see if I can start a world class collection of traffic tickets, a head rework is readily available from a company named TPIS for the LT1 giving another 150 HP, not to mention NOS worth another 100-150 HP, and I still don't have to mess up the car's elegant design.  Actually I'll probably just add either an intercooler or water/alcohol injection and call it workable.

Even with its 450+ HP though, my car is definitely not a drag racing car.  The calculated 1/4 mile times for this 3,700 lb car and 450HP with good gripping tires (but not slicks) would be in the mid to upper-12s.  That is based on times resulting from its pre-supercharger "phase 1" condition where in un-blown trim it ran an average of 14.48 seconds at an average of 96.6 mph at the Carlsbad Speedway after several runs.

On a timing run in the desert after the supercharger was in, we recorded 0-60 times on three runs of... 

1. 3.4 Seconds
2. 3.8 Seconds
3. 3.2 Seconds

The runs were made without power braking and from a solid stop, foot on the brake (because idle speed will get me going about 25-30) then just rolling the throttle to the floor.  I had a full tank of gas, spare, etc. all on board plus my friend at about 180 lbs. I was watching the road and my friend with a digital stopwatch had his head close to mine watching my speedo which was re-calibrated during the buildup due to the change in pulses from the V12. We would count down in synch to me hitting the gas.  It's not scientific but it does give an idea of the car's potential.

That may be far from impressive to any serious drag fan.  It's better than most stock vehicles on the street by quite a bit but what's the point?  More tickets and initiating some disaster?  Besides, the Vipers and the new Vettes have similar power, manual trannies, better low-end gearing, and quite a bit less weight so would probably do better. 

But not very much else in stock trim that lists for under $100,000.00 would stay with it on the open road, certainly not as it approached top speed!   

Of course I realize that without the coupe's aerodynamics (coming from the "flying buttresses") or a functioning wing/spoiler to hold it down the car would not be well connected to the road at such a speed and consequently quite dangerous, but it gives an idea of the potential. From a safe, functional point of view it is easily a 180 MPH car.

However, since it was designed and created as an efficient freeway flyer, whatever it's potential on paper, or times at the strip, it does what we designed it to do beautifully.  A trip to Colorado for the retirement dinner of a good friend proved just how great it was.  It cruised all night in triple digits and never skipped a beat. 


Fuel Efficiency

BTW, gas mileage is interesting too.  The first tank, of course, I had my foot in it all the time (I mean who could resist?) and only got about 243 miles and about 15.8 mpg.  On it's second tank of gas, I added some Octane Booster and then spent approximately 40% in city driving, 25% on the freeway at speed, and the rest in the local mountains on a twisty road drive to Julian, CA while location scouting for a workshop.  It got an average of 21.4 MPG for the tank!  I did make an effort to drive smoothly but not necessarily slowly and was, by no means, trying to do an "economy" run. 

Another variable in addition to driving style was the use of an Octane Booster. I've now done some tests and it is clear that the car gets noticeably better mileage with similar driving when I put in the booster.  This only raised the 91 Octane pump gas a few points and really could not be felt as a power difference at all.  But it tended to keep the car's knock-sensor from automatically retarding the spark.  At least that is the only rationale that seems logical since with my tall gearing I'm on the verge of lugging the engine at 1500-1750 RPM when in high gear doing 60-70MPH which is a large portion of my driving back and forth to school.  That deserves some further testing.  My speculation is that it would have little effect on a car with more normal gearing. 

Then the blower went on and I had no idea what would happen though I expected the mileage to drop a little.  To my surprise, it actually improved a little.  My best tank in unblown trim had been 24.3 mpg where I had carefully driven it in the 60-70 mph range on mostly highway.  But on a cross country trip after the blower was established, consistently on runs where I kept the speed in the 70-90 range I got 26+ mpg as long as I put in the octane booster, without it I dropped to 17 mpg. I also dropped to a 16.9 mpg average tank on one stretch where accept for acceleration and deceleration from one gas station to the next, for over 250 miles I drove at speeds rarely dropping below 110 and often much faster.  My overall average to date has been 22 mpg.

I can live with that!

Subjective Evaluation Well, I'm clearly biased, having thought this out in advance and, with Alan's input and guidance, selected components with an end goal in mind.  But I have to say, the car is everything I ever dreamed it might be... and then some.  For my tastes, I've never seen its equal in terms of a combination of elegant looks, incredible road manners, and truly mind-boggling power (for a daily driver street machine).

It is a truly elegant automobile from every possible angle.  And it is a head turner.  Of course the FlowMasters and the custom exhaust also get some attention with a truly unique sound: not a muscle car roar, but a mellow and very  throaty growl unlike virtually any modern car.  In fact the only thing I can think of in terms of sound quality that is close was the sound of early straight 8 racing machines.  

The car can be relatively docile if you just keep your foot out of it.  Though the truth is that it is hard to keep it below city speed limits without driving in a lower gear or riding the brakes.  On the level, the idle speed with no throttle AT ALL is nearly the street speed limit.  The car is quite content to just motor around if you insist.  

But pulling on to the freeway and giving it a little throttle transforms it into a completely different car.  It really just "settles in" at around 90 where it gets smooth, quiet, and seems extremely happy to stay for hours on end and at pretty reasonable gas mileage (see above).

Put your foot in it though and the "gloves come off," the exhaust takes on an aggressive but still not raucous tone.  At around 2200 RPM under acceleration it suddenly sounds like someone opened up another set of pipes. It's ready to rumble. A real stealth fighter--which is exactly what I wanted: a supercar heart in the dress of a personal luxury machine.  A Velvet Rocket.

Did I mention that I LOVE THIS CAR?

XJSC overlooking Anza Borrego SP 

I designed the plaque below to put in the cabin somewhere.  I'd like to have it made from brass and maybe go on the console.  At the moment it is a decal I placed in the Glove Box.

Design for Car Plaque


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