Current – Bonneville “Bad Cat” Jaguar

The current TMR undertaking is, The BONNEVILLE  BAD CAT JAGUAR project, which is a long term, 4 to 5 year project, researching requirements and building a 1989 V12 XJS Jaguar into a fast running salt flats cat. This project came about from having an 89 XJS, in need of quite a bit of attention.  This will provide a test platform for several theories and strategies ranging from frame and cage design, suspension modifications, performance engine modification and more..
 While others, including Jaguar themselves recently, have taken Jaguars to the salt flats, many have simply used the Jaguar body, and transplanted some other power plant into it.  Obviously, with the exception of Jaguar themselves, this is a much simpler solution to attaining incredible speeds without dwarfing the national debt.  I on the other hand, have never been known for taking the easy way out.  In fact, I can get a bit of an attitude, and dig my heals in just to prove a point.  And with that..



What to do, what to do.. Then it came to me. What a perfect solution. I like Jaguars, I like speed, and I like to build cars and try new things. PERFECT! After all, I was already half way there right! Well as it turns out, more like 20% of the way might be more accurate. After 2 years of researching and trips to Bonneville, which is just outside Wendover Utah, for Speed Week and World of Speed to become familiar with the requirements, the environment, the people and the experience in general.  It did not take long to realize that if I wanted to make this happen, and get serious about going REALLY fast, it was going to take a lot more than building a roll cage. Not that I actually thought that was all there was to it, but, a dose of reality helps you get your focus on the task.


You might initially think, what is the big deal? The V12 cars run to 150mph already.  First off, 150 wont even get you entry onto the long course, which is 7 miles long.  At less than 175, you’re making your runs on the short course which is 3 miles in length. To compound the problem, there is slippage when running on the salt.  It’s not unsimilar to driving on snow or ice. How much slippage you ask? Well, that depends on the conditions present at the time.  Experienced participants have found that anywhere from 5 to 15 percent slippage occurs. As a general rule of thumb, plan for about 10% slippage.  So, what ever your target speed, add 10% to that speed, to determine what you must run at to hit your mark.  That said, the stock production V12 normally runs to 150 on the asphalt.  That only gets you 130 or so on the salt.  That means getting the car into the 170 range just to get the equivalent of its street speed.  Then, compound that by targeting well in excess of 200 mph, or faster still, take aim on an existing record, such as the /PRO (production) class of 234 (at time of writing), and you have got a serious challenge on your hands.  Remember that 10% slippage? Well, now we start trying to get a rear wheel speed of 275 mph in order to have a realistic shot at an actual speed of 234 mph. Ever considered doing a burn out at 200 mph? Well, that’s about how this equates. It’s not unheard of to hear drivers speaking of the sideways adventures at 200.


Just to make matters a little more interesting,  Lawton “Lanky” Foushee, former chief mechanic at Group 44 Inc. , advises the XJ-S has a habit of getting light in the back end around the 200 mph speed. THAT could make things very interesting.


If that is not enough, now things get REALLY challenging. First, in most performance environments, you can solve a lot of your performance challenges by simply reducing and/or shifting the weight of the car. This primarily impacts the acceleration and handling characteristics of the car. When dealing with top speed, it is not uncommon to ADD weight to the car. This all boils down to getting the engine performance, RPM, tire circumference, transmission and differential ratios worked out to get the car up to the required speed. While you are not running a drag race, so acceleration is not the big challenge, you still have to pay attention to it as well as while the salt flats are vast, the long course is only 7 miles in length. You need all that length to squeeze every last bit of speed out of the car.


Finally, try running down to your local speed shop and digging out your credit card to purchase your hearts desire to turn your engine into the ground pounding screamer you need to go fast. Oops.. There is a problem. While it might not be quite so challenging if your home base is across the pond in the UK, it is DEFINETLY an obstacle when you are on THIS side of the Atlantic. Creative solutions and custom made components are the order of the day and THAT eats a budget up quickly.


Here we are, back from Speed Week.   As always a great event, read about it under the ‘Images’ tab, and the challenges faced to attend..


That said, feeling a little (lot) light in the pocket, but, rejuvenated and inspired from all the great vehicles, I’m motivated to get back at the car.  With a little luck (like the lottery), I’m hoping to get the safety requirements out of the way and perhaps get those licensing runs out of the way this year yet at World of Speed in September (not likely), or, more likely, at the World Finals in October.  So, I’ve got to get that roof panel finished off, get the windshield out, and get to work on the roll cage.  That’s what is in the weeks ahead.


I’ll do the best I can to get regular updates on progress.  It’s a real challenge fitting all these things into a day.  I haven’t even finished getting all the photos up from Speed Week, and only half way through the story of the trip.  Have yet to start on the information of the ‘Rest Stops and Interest points..
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  1. David says:

    Hi all,
    Reading this page, Very interesting.
    I have a 1980 XJ-S that I’m rebuilding/modifying. Low millage and 10:1 pre-HE. Soon it will be finished but I am always looking for information and suitable parts. I also have a V12 HE motor spare, etc. I would be interested in knowing. If anyone can help in, is casting details for various different heads. Either a listing or point me in the rite direction of where to find this info. I would dream to have a set of group 44 heads and as I bought this car partly restored, I would like to confirm correctness of parts or confirmation of performance parts already installed?

    My car now has a TKO600 5 speed fitted, Alloy flywheel. A 3.31:1 diff. Custom extractors (from Spitari Engineering), awaiting performance exhaust. Upgraded distributor (HE Type). Enlarged throttle Body’s, upgraded Fuel lines. Thermo fans and soon upgrading the ECU. To those in the know, when completed what would the expected HP be? and what other affordable modifications could be suggested for this setup. It is a road registered car, To be used for club events and occasional track days. Any help would be appreciated.

    • TMR says:

      Hi David..
      Sounds like an interesting project. Like anyone that has undertaken a Jaguar performance build, you soon find there is no single go to source for your performance needs.. More of a find, or create what you can, make sure you bring your wallet..
      You should maintain a photo log. Would be happy to post your story online here for you..
      Good Luck..

  2. Jorge Garcia says:

    Hi Tom,
    I recently purchased a 1986 XJS V12 coupe as part of a package deal with another car and two engines. I didn’t necessarily wanted the XJS but the whole thing was so cheap I couldn’t pass it up. I came across your site while searching the web for info on the XJS. I like what you are doing and the emphasis on “cheap” was also a major attraction.
    I’d like to build a Jaguar “nasty boy” with emphasis on performance and deal with cosmetics at a later date if ever. This would be a street and track day car not a daily driver. The one luxury I have to have is air conditioning, it gets very hot here in Texas.
    What would you recommend as far a an engine build, how much hp/tqe can I expect? At the moment I am thinking of a 3.54 ratio rear end, a conversion to a manual transmission, tubular headers, no cats, free flowing exhaust. I like your TWM induction with individual TB but at $500 per TB it’s too pricey for my budget.
    Thank you for your help.

    • TMR says:

      Welcome Jeorge
      No great surprise, you will get a lot of different opinions on where to spend your money, and where the best bang for the buck is. So much does indeed depend on your budget, and what your end result target is. Intending this to be more of a weekend warrior car, that opens a lot of doors you might not otherwise have. By that, I mean you can remove things to reduce weight.. Big advantage in the acceleration end of things.

      While the Jaguar in general, but more specifically the V12 and the XJS make a great combination, but, they are refined and luxurious. Within reason, no matter what you do to an HE engine, you will be limited by the head design. That said, I would suggest getting your ratios set up to suit your application.
      Getting into a 6 speed would certainly improve life dramatically and may be that single item to target. I believe Keisler Engineering offers conversions to provide everything in one package. Clearly, you can go through the effort, and put it all together yourself. But, one mistake and you are in a financial hole..

      Intake and exhaust are ALWAYS an issue. Getting into a dual throttle body set up, can make a big difference, and depending on your abilities, can possibly be done by you. At the least, a local machine shop can handle it for you.
      Opening up the exhaust would be the other side of this equation. If not required for street use, that is even better as you can eliminate all the other crud and just set up headers and side pipes.

      In order to reap the most benefit from ANY modification, you should be getting a performance ECU. The name that comes to mind is AJ6 Engineering from the UK, who have probably the number 1 reputation for this type of thing, and have offerings of other performance equipment for the V12.

      There will always be small things, like modifying the air boxes, or getting more fresh air in to it..
      And, at the other end, is throwing a complete build up of the engine that can run you $10 to $35g depending what all you try to do and add.
      Unless you want to get into a head swap, apart from bolt ons (headers and intake) I’d suggest the most you consider with the engine is a set up cams.. Past that, you really have to dig into the finances..

      In short, if you want to have some fun, don’t break the bank..

      Keep us informed of your progress.. Take pictures..
      If you get to the point of undertaking any aspect, keep good notes and I’ll be happy to set up a user project area for you..
      Everyone would love to follow along..

      Cheers Brother..

  3. Don Miles says:

    Please give me a ring, home is 0044 1494 729241, but maybe better is 0044 7949 944523 as I am putting lots of man hours in on 006 at the moment.

  4. Gerald says:

    Read with much interest your article on the racing V-12 Jaguar.

    Of particular interest to me is the bell housing and throwout bearing. I’m putting a 1994 6 liter in my V-12 E-Type and am going to use the original Jag 4 speed (already have a 2.88 rearend). I was going to redrill the block to accept the old bell housing, but your idea seems better. I assume you used a Chevy trans, but will the Lakewood also work with the Jag trans? Will the hydraulic throwout work on the Jag bearing collar? How do you bleed the hydraulic bearing when it’s inside a scattershield?


    Gerald Nuijen

    • TMR says:

      Hi Gerald..
      Sorry for the extended (severe) delay in replying. I’ve been having trouble with virus here..
      and, started a new company..
      All that aside….
      I’ve been hearing rumours, there may be a scatter shield available from Lakewood, already drilled to match the 6.0. Have not confirmed.. In my case, yes, using a Chevy tranny, Either way, check the dimensions before hand. Modifications a be required, but likely minimal.. The throw out bearing is available in lots of variations. Should be able to find a match I would think. Bleeding is usually done through the opening where the fork would go. Worst case, you would have to drill a hole in order to access.

      Again, my apologies for the delay..

  5. I still have them. I have the special made followers as well that allow the cam blocks to be bored slightly allowing for even larger lift cans. I was told that these were very expensive although very specific in use desirability.

    I see no need for these any longer as I sold my car and think I have passsed that point in my life where I see ever using them again.

    Contact me if interested

  6. Unless you have a non-overdrive 5 or 6 speed Chances are reasonably decent that you won’t get any benefit with a taller (2:46) rear end. Combination of frontal area and drag will overcome the power available from the engine as you discussed.. Remember at the Altitude of Bonneville you will have an extremely tough time making much over 350 horsepower.. There is a cheap way to gain the compression you’ll need for that altitude.Use the 7.8-1 compression pistons from a 5.3. (commonly used in all the early flathead engines in sedans and XJ-S) If you mill valve reliefs in the squish area of the piston you should be in that 13-1 region plus you can use stock (used) pistons which should cost you nothing . {The early XK-E V12 used 9.0-1 pistons which could get you in that 17-1 compression area which with alcohol works great at Bonneville But don’t try that combination at sea level}

    I’d suggest you don’t waste money on aftermarket rods.. The factory ran the stock rods up to 8400 RPM before the stock valve springs floated.

    Power with the ISKY XM2 cam drops off above 5000 rpm .. so for Bonneville I’d use their V1999 grind. Actually I have a few profiles that work better that I intend to get Bruce Crower at Crower cams to grind for me.. If you want I send you the specs and power Torque output numbers..I’ve never tried to get ISKY to grind custom specs so I don’t know if they will.. With Bruce Crower I simply explain what I want and he’ll grind any profile I ask him to on my cams..

  7. One other option would be to use the 6 speed transmission of the Corvette etc.. it’s a double overdrive which will get you to the same place.. Don’t forget to bring several diameter tires as well to do a cheap “quick change” based on whatever air density you run into. Stock tire diameter is about 27 inches and there are racing tires all the way up to 28.5 diameter in 15 inch sizes plus more in 18″&20″ rim sizes.. Just use Corvette rims for a cheap source of wheels..

    • TMR says:

      I’m only using the 4 speed, because I had it. I would LOVE to run the 6 speed.. But, unless someone wants to donate one, it’s unlikely I’ll have one for a while..
      Revenue Canada decided they needed my money more than I did.. THAT, has thrown a serious damper on things.
      Goodyear has some high speed tires into the 30″ range… That, and a little luck finding a high set of grears for the Dana rear, should get me into the right range..

      Still do hope to eventually add the 6 gear to allow a little more time to squeeze the top end..

  8. frenchy Dampier says:

    Why the XJ-S? While does have slightly lower CD than the XK-E It has a whole lot more frontal area. My thinking is to use an XK-E series one with a V12 stuffed into it.. Nah! The V12 won’t fit except you don’t need to use a XK-E frame.
    Take a XJ-S front and rear suspension (they just unbolt).. narrow them up to the 50 inch wide track of the series 1&2 XK-E using thin wall square tube like an XK-E make a frame that will connect the front and rear suspension and hold the V12 Using fiberglass front and rear body shells will get you a very low cost “XK-E” that you can design from the ground up for low drag.. It’s just as production as Gentilozzi’s Jag even more so since it uses a Jaguar engine rather than the Ford Engine in Gentilozzi’s car..

    You could either narrow up the stock jaguar Jteering rack or better yet replace it with a MGB steering rack.. (which also has a 50 inch track width).[just flip it for the rear steer of the XK-S {RHD} or swap spindles side to side to get front steer and leave the rack RHD] The lower arms for suspension can be easily narrowed up by any decent welder while you have your choice of using the series 1&2 dog bones (axles) or have short drive shafts made.

    • TMR says:

      I had the XJ-S just sitting.. No sense wasting a car.. It was too rusty for my liking to do much else with.. Mind you, there is no reason why the power train can’t be flipped at any time into something else.. I’ve actually been giving thought to a stream liner with the V12.. It would be interesting to see what a greasy shape would allow it to do..

      Age old battle $$$$

  9. Gene says:

    I have aquired a set of the heads you mention that were commissioned by group 44, and Lanky Foushee. Any idea of what these are worth, or anyone that may be interested in them? They are bare, never built. They have the larger cam followers with them, as Lanky said that they were very cost prohibitive one off made.

    • TMR says:

      Hi Gene..
      You’re a lucky devil to have those.. There are many that would give their eye teeth for them. All you have to do is find that person..
      While there is no price guide, being very much ‘what you can get’.. If a complete set of ready to run heads, I’d think bidding would start at $1000 perhaps and go from there based on demand, perhaps making 2 or 3 g.. But, not complete/built, it’s any ones guess.
      There is no getting around it, these are THE heads to make power with, Just need the buyer..

      I’d think Jag Lovers would be one of the best places to try and move them. Who knows, maybe this post might get some attention for you..

    • TMR says:

      Gene, I just thought of something..
      You might want to touch base with Steve Moore, the current owner of the Group 44 XJS.
      He may be interested, or know of someone that is..

      Tell you what, I’ll drop him a note with your email..

    • Hello Gene,

      Please contact me so we could discuss possible purchase?

      • TMR says:

        Contacted Gene.. Here’s the situation.. Drop him a line..

        Gene Holtzclaw says:

        September 25, 2012 at 8:26 pm (Edit)

        I still have them. I have the special made followers as well that allow the cam blocks to be bored slightly allowing for even larger lift cans. I was told that these were very expensive although very specific in use desirability.

        I see no need for these any longer as I sold my car and think I have passsed that point in my life where I see ever using them again.

        Contact me if interested

    • Bob says:

      Hi Tom,

      I’m the captain of a new race team in Ontario. We have an XJS we intend to get serious about. The car has been seriously lightened, cut and set up. We have a 5.3 in the car and are ready to get some serious power out of the v12. Are the heads still for sale.

      Best regards


      • TMR says:

        Hi Bob..
        Spoke with Gene, and here’s his situation..

        Gene Holtzclaw says:

        September 25, 2012 at 8:26 pm (Edit)

        I still have them. I have the special made followers as well that allow the cam blocks to be bored slightly allowing for even larger lift cans. I was told that these were very expensive although very specific in use desirability.

        I see no need for these any longer as I sold my car and think I have passsed that point in my life where I see ever using them again.

        Contact me if interested

    • Don Miles says:

      Can I have the heads please, I run an XJR5 006 which I have raced for the last 12 years, need a spare engine as to remain competitive I have had to up the power at the cost of reliability. This is the most raced XJR in the world, the Miami GP winner and the only XJR5 raced in serious competition for the last 12 years. Need to know the numbers on the heads, should be on the front outside of both A & B , on the A by the removable cam chain tensioning bung, May start CA- and then 3 numbers.
      Know exactly what the heads are and whats needed to complete a pair so I wont be a future pain in the butt and they will be going to the right kind of place too.
      |Regards Don Miles, if you want to see the car just search Don Miles Jaguar or XJR5 006

  10. Michael says:

    Hello Tom ,

    How is your V12 engine project going is the engine running ?

    Best regards michael .

    • TMR says:

      Hi Michael. Good to hear from you.
      Well, true to form, may things in my life have delayed the project for me.
      However, the engine has been running to about the 170mph with 2.45 gearing and dual throttle intakes, with more left in her. Likely 180ish..
      Now the new injection system installed, but haven’t got the new TEC3 electronics set up yet. Then, need to find a lower set of gears for the Dana rear..

      • Michael says:

        Good to hear that its running already hope that the new injection system will work fine and not to much trouble to modify everything again .

        Where are you located in Canada ? I am from Belgium, but this summer I come for 3 weeks to Canada to visit my dad that lives in Pickering near toronto .

        Best regards michael .

        • TMR says:

          Located in Saskatoon Saskatchewan. Quite a way from Pickering..
          I noticed that I mis spoke when I mentioned the gear ratio.. I am hoping to FIND a set of 2.45 (ish) for the Dana.. Currently have the stock 2.76 (if memory serves)
          With a boost in tire diameter, I should have an end result over all ratio to get me there..

  11. TMR says:

    Hi Steve. Thanks for dropping in, and for leaving a couple thoughts. Very nice to hear some ‘facts’ about the car. I have many pictures of the 44 car around the shop, and use them for reference regularly. Plus, as a source of motivation when I get in a rut. Kind of falling behind on updating the project page, and on the project it’s self. Summer is too short here, so other ‘outdoor’ activities and projects take priority. Just acquired an acreage as I have run out of space in current location. Trucks, trailers and cars taking more space than I have. So, that will create additional demand on both financial and time resources. Fall is approaching, so should be able to get back at the car soon. Still hoping to get down this next season and atleast get the basics out of the way.

    It would be great if you stop in now and tehn to let us know when you have the car out for a run at an event..

    Thanks again

  12. Steve Moore says:

    Good luck with the project Tom, we are the current owners of the Worlds Fastest XJS. It is the Group 44 XJS Trans Am / IMSA race car that was clocked at 194mph on the banking at Daytona in 1982. Bill Adam mentioned that she did get light in the rear end but would hold when set going around the banking.

  13. I just want you to know I posted at so my friends can see it too. I used Tom Mackie Racing » Current – Bonneville “Bad Kitty” Jaguar as the entry title in my bookmark, as I figured it would be a great way to spread the word about this cool post. Please email me back at if there is anything else I can do to help.

  14. admin says:

    A few years back, when I first planned this project, I mentioned to Jaguar Canada my interest in putting a Jaguar on the flats asking for their involvemet. I was never given a reply. Perhaps this is why. Paul Gentilozzi of Rocketsports Racing, fielded a Jaguar XFR and claimed the record for the fastest Production Jaguar @ 225 mph on the Bonneville salt flats.

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