There are many companies in Europe that are in your country or will ship, just do a Google search. You should search locally for, (engine builders, automotive machine shops, automotive engine builders); there are many car enthusiasts in France so there must be options. Also there are many places that will ship parts to you as they ship worldwide both for performance parts as well as complete engines. Most of the performance makers of pistons, cranks, etc. will make custom sizes so by boring you can then get a larger displacement and have more options, here are a couple:

https://www.serckmotorsport.co.uk/br...SABEgL3yvD_BwE
https://www.bar-tek-tuning.com/produ...t-pistons/?p=1

Also there are many people in the USA whom will ship worldwide, here is one that specializes in high performance Jaguar both in parts and full engines from mild to very high performance,
Team CJ custom forged pistons
Team CJ Jaguar Engine Stroker Kits
https://www.enginebuildermag.com/202...l-engine-work/

Pierre,
Some people are purists whom are more collectors that do not put much miles on their car as they are just for show, etc. They are thus opposed to anything being not stock. Improving the internals on any engine is where you get the most benefit and you can do so and keep the car a street car but with improved performance and longevity in the engine, especially when you have already taken the many hours to tear the car down as you have already. Remember stronger, lighter internals will greatly improve things as you are reducing the rotating mass/weight and those performance forged parts are much stronger and will last longer. You really should NOT use any of the old internal parts in my opinion as there are much better made, lighter, stronger, high performance parts you can rebuild the engine to provide a longer life and more efficient engine that will give you more power reliably.

 

Indeed & yet time & time again people mess it up.

 

Hi Primaz
I agree with your writing but my only problem is that my engine is a 2.4 litre and for this model the available choice of spare parts is alot more reduced compared to 3.4, 3,8 or 4.2 litre engines ... :-(
I have done more than 50000 km as daily driver with this car when I was student , sommer and winter, snow or icy salted roads and I can say it was reliable :-)
:-)

 

Pierre W
There is something wrong in the ring system. Where did you source the "new" rings.? Did they really know what they were selling!
Do you happen to have the old rings or bits of them as that would give you a guide to the original thickness of the rings.
I have never heard of pistons deforming to allow such "loose" tolerances as you quote for the rings. Some where, some thing is incorrect and I suspect the rings supplied are incorrect.
I can assure you we had some very "agricultural" fixes in my youth in Australia. The things we did to GMH Holden motors should not be repeated.
But we did not have ring problems even in loose worn out motors provided the rings fitted the piston groove. I have never seen this groove expand in heaps of engines I have rebuilt
I really urge you to consult with an accredited engine rebuilder as to the "state" of the engine and the correct size rings..
Piston rings come in all different sizes and thickness etc. They are not specifically made for "Jaguar"..
By the way don't let anyone touch your crankshaft. Unless it has had a severe oil pump failure or something similar it should be good for 300K+
Bon Soir
Bill Mac
MK1
MK2
S3XJ6
X300
15 previous Jags MK5 to X308

 

Another thought which would give you more power is just find a 4.2 or 3.8 Jaguar in line six to either rebuild or buy one already rebuilt.

Again for internals there are many companies that will make custom pistons, rings, cranks, valves, etc. As Bill stated rings are not just for Jaguars. It is common for engines to be bored larger so getting pistons, rings, etc. have many options.

 

Don't let old technology get in the way of practicality and usability.
Keeping things original as much as possible will work using old engine designs, but things have come such a long way with metallurgy that it doesn't make sense anymore not to use what's available nowadays.

Even more so on a car that has an outdated engine.
Jaguar did not do this so much, because their cars were not hand built, but it was common for Rolls Royce to install an updated engine in a car as things improved.
One can keep a matching numbers car "just that" in a Jaguar, changing out to forged pistons and modern ring designs will not devalue the car, in fact it will make it a more desirable car.
It will come more reliable, run cooler and last longer.

The new rings will be matched to the design of the new pistons with shorter skirts.
So will the wrist pins and the snap rings that hold the wrist pins in place.