While those can be an ok choice, those engines are more like 250 to 300 HP but I am sure you can modify them to get some more. TJ is in the US so the GM LS is a way better choice as it is only around 60 lbs more in weight with much more power, reliability and options for performance parts which is especially helpful for swaps. If he was in the UK that could be an option but in the UK a better swap to me would be the Nissan RB twin cam or the Toyota JZ twin cam as both of those will put down the 400-500 HP and have great reliability. My experience is that 400 HP is good and 500 HP would be awesome so if you are only getting around 300 HP it is nice but just not enough.

 

The LS small block aluminum block/head V8's are at that 420 lb weight level but provide easily much more power than the Damiler V8's ever could as those even with the 4.5 liter were not very powerful at all. The LS V8's will easily do 300,000 miles + reliably both stock and built. It is always best to use a powerplant that has proven reliability and power so if you have the funds to improve it you are not creating reliability issues.

My car is a Jaguar 3.8s and on the rear end all I did was strengthen the rear lower control arms (there is a weld it brace already designed for around $100) and did a little extra simple bracing of the IRS assembly. On suspension the rear is easy with QA1 adjustable coil overs, and the front I had some custom lower control arms made and used the same QA1 adjustable coil overs. Brakes I used the Fosseyway 6 piston kit which works with the stock setup and very good, and the rear I upgraded to early E type larger brakes. I also upgraded to 17" x 8.5" with 245 wide tires on all four corners. Those upgrades make the car handle way better than stock and easily handles the increased horsepower with ease. Thus it is not hard to make a few mods to make it an all purpose daily driven car for luxury when cruising at mild speeds, to mountain curves pushing the limits in any road. My old LS1 took posted curves at 1.5 to 2X times faster and I took it up to 130 mph. I do not see these cars being a top speed car trying to chase over 150 but with the increased power and some mods they can hold their own against today's expensive sport sedans from 0-130 mph with no issues.

I do not know how the solid rear MKII axle is or if you can swap a Jag IRS setup? but I believe that is possible as the Calum MKII has an IRS setup.

TJ sounds pretty experienced with mechanical work so that is a big plus as any swap faces challenges. TJ, just never give up as the end result will be so satisfying!

 

Glyn, you are spot on! I shared a lot here on the forums but being the first is often very frustrating and many others would give up. You have to have a lot of tenacity and more $$ when you do something first and TJ is on a budget so doing something unproven will easily blow his budget.

 

Primaz is actually the first one of these I've seen swapped with pictures and details, was years ago. (I've had this car for 10 years in storage now) now that I'm getting closer to actually starting on this, his writeup is a big reason I chose this route. Lol. I'm glad there are people who have modded these to have an LS, and there is some kind of support. I have seen a few on the web now that have swapped an LS in these girls. I have a long road ahead of me. But this car isn't going anywhere and will get done.

 

I wasn't for a moment suggesting a Damiler v8 be used, although I think they are a lovely engine and I was only saying the weight of the 2.5 unit gave the car better handling. The 4.5 was actually much more powerful than the 4.2 XK. They put one in a Mark 10 to evaluate it and found it would easily do 135 mph.

Of course a modern V8 is of course both lighter and more powerful. This side of the pond, there are some nice modern 6 cylinder units that would be worth considering.

 

The Jaguar version of the Duratec V6 appears to be the engine of choice for Mazda Miata V6 conversions; there is a good deal of support out there for this, particularly in the area of stand-alone EFI units and manifolding. Re-inventing the wheel is often frustrating and expensive...

 

Ah yes, the Mk 2 is a revamp of the mid 50s Mk1 and there were no motorways in Europe in those days except in Belgium and Germany. Many people were running side valve engines and 3 speed transmissions and screamed "mad sod" if anyone came through their village at more than 20 mph. Oh and tax laws that taxed an engine based on cylinder bore resulted in long stroke engines with heavy blocks. And of course the XK was made on tooling bought second hand from Standard so inherited that foundation.

I once had an X-type with the 2.1 Duratec V6 and it was a very sweet revvy motor, I can see it would have been a nice match in the MX5. I ran MX5s for many years but the engines were bomb proof even after 250k miles and the object was trouble free daily driver. If I had an engine failure I would have considered the Duratec.

I tried an XF with the 3.0 Duratec and I felt it was having a hard time under spirited driving. In the aluminium bodied XJ, the small V6 had a much easier time given the lower weight. So I opted for the V8 XF which was not quite so sweet but still a creamy smooth ride. I think the torque curve is more important than max power for heavier vehicles.

I think friends on this thread are looking for straight line drag performance, rather than euro style cross country fun. So the crate V8 is attractive.

I once had a Rover V8 engine spare and considered it for the Damiler V8. I liked the design of the Buick derived V8 and it's light weight. However, despite an extra 1000cc and running a 10.5 compression ratio it only produced a handful of extra horsepower and couldn't run above 5000 rpm for long periods. I would have had to change the rear axle ratio to get acceptable motorway cruising. The Damiler engine was comfortable beyond 6000. When I dismantled it, I could see why it was expensive to produce, beautiful light weight components. The Rover V8 was easy to work on and quick to assemble, but the Daimler V8 required careful assembly with fine tweaking of fits and clearances. After a careful rebuild it ran 150k miles with no problems before I sold it. The iron block made it quieter than the Rover unit.

The other things is that I had the radiator rebuilt to the tropical specification listed in the factory service manual. I never had any overheating issues and wish Jaguar had done that as standard on all their models - but the extra copper in the core was no doubt too expensive.

I know Jaguar made a 9.25 litre V8 for the military with quad cams and 4 valves per cylinder but they were never happy with the refinement and I heard most finished their lives in tractor pulling competitions. Now that would have been too heavy in a Mk 2!

 

For me I do want "Euro Style Cross Country Fun" but at a performance level of today's high dollar Euro sedans and that does require for the weight of the Jaguar sedan about 400-500 HP.

I do agree on your side of the pond, if I lived there the Toyota JZ or Nissan RB twin cam both produce very reliable big horsepower and will easily do 400-500 HP without much effort and be super reliable. In fact Retro Power in the UK has built one of the nicest MKII with the JZ twin cam. The problem for Jaguars is that quality Euro style modified Jaguars are really only done by Retro Power & Beacham, both big $$ companies with cars easily $175K to over $300K. The other issues are that they will not share their secrets of how they build them and unfortunately Jaguar owners often are against modifications which create a situation where you basically are on your own with no help or assistance. While the Toyota & Nissan create the power & are a straight 6 so it might seem easy but, I am sure there are many custom fabricated parts needed for the swap and maybe it is easier in the UK to find a tuner for those but here in the USA a GM LS has an enormous amount of vendors making parts specifically for swapping them into other cars and tuners are plentiful here for the LS.

Doug on this forum whom has built a couple of MKII with V8's was very helpful but with such little help you really need to think hard about doing something for the first time for this brand of automobiles. There is another forum, BritishV8 Forum: that can be very helpful but unless you are a master fabricator or if money is not much of a concern I find that being the first for Jaguar mods is not an easy task. To keep up with today's BMW, Mercedes, and other Euro performance sedans you need enough power to match their 0-60 and handling so for the Jag sedans 400+ will do it, 300 or less you will be under powered. Yes you do not want to put a heavier engine, but to be competitive you will need to have a little bit of an advantage on power to compensate for all of their other high tech suspension designs, etc. I know from real street driving that 400 HP with improved coil overs, lowering the car and wider tires the Jag can keep up with all of them and surpass some of today's euro performance sedans