Avoid 4.2 pre Series 3 XJ6 engines?

Ok, well I am just going to throw it out there…

Upon reading all I could find on the subject, and having owned Jaguars of the time period Post 66 and pre 1981 when the bore repair was done curing the cracking issue btw bores of the 4.2 on the Series 3 XJ6.

Should they be avoided? Are they considered lemons therefore? Better to replace block/engine with a Series 3 XJ?

Are cracks (as I seem to read elsewhere) inevitable necessitating top hat liners?

Are those around today running well to be considered survivors, cast and cooled properly (an apparent Leyland issue) etc…?

As that is something I really would not want to deal with down the line.

I just had to ask. I always considered the XK bulletproof until recent reading.


all the post '68 motors have long studs which are not great on 30+ yr old motor, they can rust thru near the base (and snap), bore wear also an issue at this age, al head/iron block junction is not ideal either,
pre-S3 motors are supposed to be LESS crack prone I believe


Yes, I’m aware of the stud issues, that doesn’t concern me so as it can be remedied with proper attention after replacement.

However the cracks between bores of the pre S3 (post 68_)motors is well documented.

I won’t get into details as it is well documented, but it all has left me a bit confused really.
While forums aren’t the best place for such questions as one gets usually a multitude of completely contradicting answers, I had to ask.

I suppose I am looking for something definitive.
I’ve read of Leyland casting issues that may be the result of such cracks, that is a design flaw, etc. remedied only with “top hat” liners.

Or are they a result of overheating only?

Anyway, must be a dumb question, no responses.

Best wishes with your project. Be careful

some substantial reading matter on this topic

as you mentioned though, there is not complete agreement on the topic


Yep…read that through a few times now.
Thank you though…

Ah hell, I’ll read it again.

Edit: Ah well, upon researching more i get it…and see why you stated the 7L was less crack prone as it was apparently more robust.
Important to note, the 8L referred to as also problematic is pre series 3 update.

Funny, all these years i never knew, never had a problem.

These are outstanding articles on subject, including photo of rebuild process I’d never found before.

Top hat liners are the solution …sigh. The sh*t we do for cars.
Not as expensive as imagined though…
The aj6 was a big improvement although not nearly as charismatic or pretty.

Excuse me, to most here must seem like I’m reinventing the wheel.

Kind regards