Abandoned XK Engine Projects

Recently discovered the XK100 article on the Old Site and interested in finding out about other unproduced XK related engine projects such as the 2-litre XK6 and the motorsport focused 3-litre XK6 (particularly whether the latter was based on the short-block or long-block version as well as why both engine were not produced)?

Also while the 105 hp 2-litre XK100 / XK4 was considered to be too low powered and unrefined as well as seemingly obsolete due to Jaguar’s rising image, how would Jaguar have fared had they produced the engine? And could a filtering down of the XK6 developments and tuning have been enough to remedy the relative lack of power and refinement of the 2-litre XK100 / XK4 engine for it to produce similar power to the 2-litre Alfa Romeo Twin-Cam or more?

Additionally given that Jaguar during the 1960s did look at a Coventry Climax V8 powered XJ Junior project of similar dimensions to the Alfa Romeo Giulia in order to challenge the Rover P6 and Triumph 2000/2500, could Jaguar have anticipated the growth of the UK 2-litre executive saloon segment before Rover and Triumph via a 2-litre Mk1/Mk2 variant or a related smaller saloon?

The 2 Litre Type XK100 engine was advertised, with a dedicated half page, showing all specifications in the large maroon XK120 brochure - at least into the 1952 model year. However, I suspect that this might have been an advertising ploy to present the image that Jaguar had more than one engine to offer.

Jaguar’s largest market was the USA. At that time, the American market was captivated by the new V8 engines, horse power, and displacement. Jaguar could not have seriously thought that it could compete in this market with a four cylinder engine in a premium priced automobile. If anything, Jaguar was looking to increase the horse power and displacement of its original 160 HP, 3.4 litre XK engine to better compete in the American market.

There were other engineering improvements Jaguar needed in the early 1950s that would likely have taken priority over further development of a wimpy 4 cylinder version of the XK engine, i.e., brakes and gearboxes to name two.

I often wonder the same…alas, no joy.

Obviously the 2-litre XK100 engine would be unsuitable for the US market (except possibility during the later fuel crises down the line), which is why info elsewhere mentions it being UK market only (with the possibly in retrospect of later penetrating certain European markets where large displacement engines above 2-litres are heavily taxed).

At the same time this was also the post-war period where carmakers looked at Big Fours typically derived from Inline-6s (like the early Big Healey) with the former in turn potentially being capable of spawning V8s via doubled-up 4-cylinder engines, notwithstanding Jaguar’s size and the costs involved at the time.

Not sure if Jaguar even investigated any V8 projects (XK-based or not) during that period aside from the rough V12-derived 60-degree V8 and the non-Jaguar Daimler V8, if Sir William Lyon’s autobiography is any indication regarding Edward Turner’s proposal during the war the latter V8 in some form could have potentially ended up being fully Jaguar from the outset (with a designer by the name of Leonardo Fioravanti even developing a Slant-4 version of the Daimler V8 for his thesis one time).


Did Jaguar have the production capacity at the time to produce a smaller saloon below the Mk1/MK2 prior to being acquired by BMC or would Jaguar at best have only been able to produce entry-level 2-litre XK100 powered versions of the Mk1/Mk2?

The XK100 has come up for discussion occasionally on the XK forum.

It was considered for the Mark 1, but they couldn’t solve the second order vibration problem without counter-rotating balance shafts, so the project went no farther.

They made a V8 in 1954. Again apparently found no customers.

Been awhile since I wrapped my head around issues like that: Found a reasonably-easy read on the subject.


Thanks for the info, shame the project never went further as a tuned road-going version of the 2-litre XK100 engine could have potentially put out a decent amount of power compared to later 2-litre Twin-Cam engines from other marques.

Regarding the Jaguar V8 engine. If Jaguar’s biggest market was the V8-loving US, why did they design a V8 primarily for military applications or could the V8 have also potentially formed the basis for a non-military version of the V8 at a more reasonable displacement to power Jaguar’s own cars (along similar lines to the Rolls-Royce FB60 Inline-6)?

Jaguar did have access in the 60s to the 4.5L V8 Daimler? engine, and fitted it along with V12 and XK engines to the MK10 prototype, the story is the V8 was so much faster they felt it was not possible to offer it without making the XK-powered version seem inadadequate

There were plans to stretch the Daimler V8 to 5-litres, interestingly it seems that the existing 4.5-litre Daimler V8’s true output actually a lot higher than the quoted 220 hp since the maximum power output on Daimler’s own dyno was 220 hp.

Though it is understandable why Jaguar never adopted the Daimler V8 as its own, they could have benefited from it and is certainly a better alternative than what BL had planned.

For an engine that didn’t get made, there sure are a bunch of them around.

The ads I have talk about the XK100 with the new four cylinder engine. The Ads appeared in Speed Age in the 50’s.

Jaguar had good experience with 4 cylinders in their line up. Their four cylinder production was considerable on their side of the pond.

Jaguar decided the sales would not only cannibalize the XK120’s numbers but would have stiff competition from the Austin Healey 100. It was also thought that the less than stellar performance of a 4-cylinder XK might hurt the reputation of the company and the 120.