Apologies in advance though thought the following was relevant given the Jaguar Mark 2 formed the basis of the Daimler V8 engined variations.
Anyway beyond the 1954 military engine, the Daimler V8 and the unbuilt V12-based V8 is it known what other V8 engine projects Jaguar experimented with during this period (or even prior)?
Given Jaguar was looking to build upon its success it is surprising they never thought about developing an in-house V8 project aimed at the US.
Armstrong-Siddeley for example allegedly developed an 200+ hp 4.6 V8 (with Twin-Cams envisaged though not necessarily implemented) derived from a pair of Sapphire 234 engines (and also looked at a 2.7 4-cylinder derived from the 4-litre Star Sapphire 6-cylinder, which would have in turn potentially allowed for a 5.3 V8) prior to ceasing car production.
What prevented Jaguar from taking a similar approach to Armstrong-Siddeley in creating in-house 4.6-5.0 (roughly 4588-5040cc) V8s derived from the 3.4-3.8 XK6s via a pair of XK4s (or XK6s minus 2-cylinders)?
The one off XJ13 had a V-12 with cylinder heads that looked much like XK heads. It was so massive that it was impractical to fit this engine into a production car. I suspect a V8 version would also have been too wide for easy use. Hence the development of the single OHC V-12 that was made for many years in 5.3 and later 6.0 displacements. Engine technology moves forward all the time and this engine was replaced with the AJV8 that addressed many of the chronic oil leakage issues suffered by the V-12 over the decades. If Jaguar had, in the 1960s, wanted a V-8 there was always the Edward Turner designed 4.4 liter hemi head V-8 as used in the large Daimler Majestic Major car.
Would be content if a V8 (with some carry over from the XK6) was developed and could only be fitted into the larger models from say the Mark VII or VIII up to the Mark X, yet it would be a bonus if such a V8 could be fitted to other Jaguar models. Perhaps even later benefiting from developments with the experimental all-alloy 3.8 and 2.6-3.0 XK6 engines, prior to being replaced by the V12 (and a successful 90-degree V8 successor that still carried over much of the V12’s architecture).
Would like to believe there was a way for Jaguar to be less resistant to using the Daimler V8 beyond the Daimlerized Jaguar Mark 2s.
Have read of William Lyons and Edward Turner corresponding to each other during the war on a proposed motorcycle project that never became to be, which along with the prospect of Jaguar later acquiring say Triumph Motorcycles from Jack Sangster (in place of BSA) had the proposed plan been a success, together with Turner’s involvement with Jaguar in such a scenario would have potentially allowed him to develop a viable early precursor to the Daimler V8 that may or may not feature Twin-Cams.