Replacement Heads

Has anyone had an experience with replacement heads for the XK engine? I’ve seen some businesses claiming increased BHP with their heads?

Bit like most things , depends on how much cash you want to spend ,
Straight port head is better then the standard , and I guess the big valve head off a XJ6 series 3 is better then the standard straight port .
Then you can have the ports polished , higher lift cams and so on !

Do you mean crosthwaithe-gardiner madness or polished S3 heads for which the book ‚Powertuning the XK Engine‘ has good Information and which will be cheaper: yes, you can make the heads make much more power.

Thanks David, Guess I’m trying to work out how much can be done with the existing head or whether an off the shelf head would work on a very fast road engine. A driver which does track days rather than a race car. I’ve seen Retro Gusto website but the site doesn’t have a
lot of info and Crosthwaite n Gardiner I thought were more for the out and out racers.

Thanks Ian, trying to work out what works and what doesn’t I suppose

There is more then one way to skin a cat (jaguar) lol
I found this book on e-bay one day a good few years back , can’t say it’s good or bad , but it has useful information in it .
If it was me , think I would buy a 4.2 XJ6 series 3 engine , like this , all ready to go , bolt a inlet manifold and 2" inch carbs on it !

Second that and this Is the book I meant!

If your in the US you should talk to Bill Terry as he’s been doing the type of work that your talking about for I’d guess at least 40 years!

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Greetings All,

Predator? I believe. They were making a wide angle D-Type style head.

Were not inexpensive, but there was a gain in HP.

Articcle on RestoGusto coming in Jan-Feb Jaguar Journal, out at nd of December. Bolt on 70 bhp with no other changes but you need deep pockets, same as wide angle. You could try Denis Welch Motorsport in the UK for CNC-ported heads and race-winning pedigree. How fast can you afford to go?

Good question!?

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Thanks Peter, Which Jaguar Journal would that be? Is it a UK, US or other domain? And how does one get a copy? Txs

JJ is the world’s oldest Jaguar magazine, serving US, Canada & Mexico. See

If you click on Merchandise and then the JCNA Publications tab, scroll about halfway down and you’ll see an option to buy the current issue. That means Nov-Dec at the moment, but at the end of December it will mean the Jan-Feb issue which will feature RestoGusto.

From memory, the next item you scroll to is a USB stick containing 60 years of JJ archive issues from 1955-2015 - all searchable by text and with many pix not published elsewhere.

Thanks Peter,



That RestoGusto head looks insane… so much want…

Thanks Robert, Guess I’m still learning who, how, and what!