Does anyone have any authenticated information/history about the infamous 4.5 litre Daimler hemi powered Mark X? The reason I ask is because I have what is purportedly the engine from this car, which came to me via a German owner who was going to put it in a Daimler 250, and who had acquired it from the late Ron Beaty of Forward Engineering. But the project foundered and I acquired the engine a few years ago. It has been professionally fully rebuilt and is sitting in my workshop awaiting a suitable home.

I had heard that the engine was not exactly left stock - bored out to 5 litres with a hot cam and forged high compression pistons - this may be 'urban legend' but perhaps someone can shed some light on this. According to Heiner Stertkamp in his authoritative book 'Jaguar', the Daimler powered Mk X reduced the 0-60 mph time from 11 seconds to 6 seconds and increased the top speed to 130 mph - at the expense of fuel consumption.

Does anyone know the chassis number of the original Mark X it was transplanted into and whether that car is still in existence?

 

Here are a couple of photos of the actual engine....

 

I would venture a guess that the V8 MK 10 no longer exists, if it ever did as a complete, production car. Paul Skilleter in "Jaguar Saloon Cars" on p. 316 has a photo of the car at MIRA being absolutely flogged around a curve. The car is identified as a prototype, carries the trade plate "321 DU" rather than a normal UK registration, and looks to be significantly unfinished (no bumpers, all trim omitted, etc). To me that suggests it was only a prototype, run with the V8 by the development boffins just for grins, and then embarassingly disposed of. But of course that is only my guess.

Have you enquired of the experts at:
The Jaguar Mk10 & 420G Owners Symposium

 

Embarrassing might be the right word. Apparently William Heynes "Lost his composure" when he learned how much quicker it was than the then 3.8 powered Mk X. This on the car from AROnline:

The second was a 4561cc V8 which produced 220bhp at 5500rpm and an impressive torque figure of 283lb ft at 3200rpm. This V8 was fitted to the Daimler Majestic Major which was in production from 1959 to 1968. Sales of the latter were low but it could match the Jaguar MkX for top speed and beat it on acceleration quite handsomely. The logical next step was to try and fit the 4.5-litre V8 into the Zenith bodyshell to create a Daimler version of the MkX, which was duly done. Physically the V8 fitted into the engine bay quite easily, and ex-development engineer Ron Beaty recalled how it performed.
‘It lopped six seconds off the 0-100mph time, and that was with square cut exhaust manifolds and an air cleaner you wouldn’t put on a lawnmower. It buzzed around MIRA all day at 133/134mph in the hands of anyone who happened to be about’.
Around this time Jaguar Technical Director William Heynes wrote to chairman Sir William Lyons on the subject of the larger Daimler V8: ‘There is no question that the horsepower can be brought up by redesign of the valve ports. At the same time I feel it is desirable to increase the capacity of the engine. I have therefore arranged with Daimler to revise the design to bring the capacity up to five-litres which, with revised valve ports, should produce 280/290bhp at 5000rpm with a 30% increase in maximum torque over the Jaguar 3.8 engine. The unit in this condition would give a satisfactory alternative unit for the Zenith (MkX) and also a satisfying performance in the big Daimler saloon’.
In the event the company decided not to proceed with a Daimler V8 version of the Zenith saloon. The official reason was that the the Daimler production line was not tooled up for quantity production, but it had no trouble supplying demand for the smaller 2.5-litre V8. Perhaps the real reason was one of prestige. A 5-litre Daimler Zenith would have embarrased the XK engined Jaguars in the performance stakes, Jaguar’s engine designers also had a blind prejudice against the V8 configuration, which they thought could not match six and twelve cylinder for refinement and they thought they could design a superior V12 engine.

 

That engine is totally news to me , what a shame they didn't sell it .I reckon this could have brought more feathers to Jaguar hat had they acted bravely