I don't see the point in changing an engine from the original to a more modern V8. Both will cost to either rebuild or buy the difference is a rebuilt engine means it is basically new as all the bearings are new, new pistons with a rebore and rings, new seals and gaskets, valves re ground, crank shaft ground and balanced. Possibly better then when new in the 60s and good for a 100k miles again which it will never do if kept as a classic/show second car.
For the same cost of a rebuild you can buy a secondhand more modern and more powerful V8 but do you really know the history/mileage of the engine and will it need a rebuild in a couple of years time itself. Add to this the hassle of mating the new engine up with the old gear box or the expense of fitting a new gear box, engine mounts, throttle linkages, choke, possibly updating the electrics for fuel injection, fuel pumps, linking the new headers to the old exhaust or having a new one made to fit. No doubt with a more powerful engine you will want or possibly need to update the brakes. Then on top of this you have the depreciation value of the car as you have altered it from the original.
Personally I would have the original sweet Turner V8 rebuilt by a specialist who will upgrade the engine with modern parts eliminating most of the original grumbles the engine had when designed. Who needs more power when the car already puts a grin on your face everytime you take it out. People admire the car not what is under the bonnet and how fast it can go. Want modern go buy a modern car.

 

It’s one of those discussions where I can’t disagree with anyone. I guess it’s up to the owner to decide what to do with his car and for the rest of us to respect it. And, of course, give our best advice, as always. There are some most impressive rest-mods on this forum, but it’s worth noting that they cost a lot of time. Doug Doreen started telling us about his XJR Mark 2 project in 2013, when he’d already started, and he got through shake down at the end of last year! Transplants are not simple. The first questions in engineering design are (1) will it geometrically fit together? (2) can it be physically be assembled (no screws to be tightened from the inside)? (3) how much will it cost? My own Mk2 project is a compromise, constrained by those three questions plus what the DVLA allows without the car losing its historic status. And, of course, at my age, the possibility of ever getting to drive the thing.

The space under the bonnet of a Mk2 is quite tight. Even transplanting the head and inlet manifold of a series 3 XJ into a Mk2 leads to a geometric clash of the manifold with the steering column that has to be resolved. I suspect geometric limitations were the main driver in the re-design of the exhaust manifolds of the Daimler V8 rather than any desire to restrict its performance. The same issues hit the Rover V8 when various BL groups tried to install it in other chassis. The fact is that Jaguar engineers did a lot of work to make the Daimler engine more robust and easier to manufacture and install. I can assure you that when you’ve done all that work, you don’t deliberately do anything to undermine it.

My impression is that Jaguar kept the engine alive to maintain some distinction of the Daimler marque, but, in the end, it wasn’t attractive financially. At the end of the 1960s Jaguar had two other prospective small V8s. One was the cut down V12, which, with a 60-degree V, never proved smooth enough. The other was to productionise the Coventry Climax F1 engine. I suspect it was the latter that Sir William planned to put into his little coupe that hit the buffers within BMC/BL.

Undoubtedly, Turner was an able engineer, but he and his designs may have suffered from his unrivalled position in BSA/Triumph. Certainly, it was the case in the later days of BSA-Triumph. Though Jaguar’s engineering team was extremely small by any standards, Heynes, Knight, Hassan, Bailey, Munday …. had the huge advantage of each other – all respected voices to criticise. That’s something no good or great engineer can do without.

 

Thanks for all the comments and the different views,
to me this is just another old car that I have wanted since I were younger and due to having familys and life in general have only now been able get one and tick it off the list. This car was bought cheaply due to not being used for 20+ years and will be put back on the road on a shoestring budget, (it does run and drive)
for the past ten years I have been scratching lots of itches mainly Triumph, (3 stags, 2 tr6, 2gt6, and 2000 saloon) not got any now though and have been looking for an xj6 for sometime, never thinking I could afford a jag mk2 I then started looking at these.
no engine swop for me I like the original to much and really do not see the point.
I will no doubt be asking lots of silly questions but this looks like a place with most of the answers.
Steve.

 

Following on Peter's comment. I think that up front a decision requires to be made as to whether you want to do a restomod like Clyde's Mk2 etc. or whether you want to maintain some originality. There is no right or wrong. It's personal preference. I'm pleased personally that you intend the original approach. There are many things that can be done in the modern era to ameliorate issues of the past. If you know the Triumph Stag well that troublesome engine can be rendered totally reliable today as can the MGA Twin Cam, Astons etc. etc.. It's also country specific. Modifying cars in SA, as an example, be they modern or classic immediately ruins their value. To me one of the great things about original classics is that they generally don't depreciate if looked after.

Totally unseen improvements can be made that keep things looking original. The Daimler V8 was even put through stringent NVH evaluation by the Jaguar engineering team.

There is no such thing as a silly question. Only an area where you don't have the experience. e.g. I'm not a gynecologist. Ask away. Collective experience here should find somebody that can answer you.


All this said. If it was a valuable car like an Aston Martin DB4 GT Zagato with so few built I would protest loudly at any sort of modification & consider it a sin. (19 originals built, 4 Sanction II and 2 Sanction III = 25 Total.)