Does anyone manufacture new XK 4.2 engines, anywhere? Cast-iron or aluminium?
I remember reading a while ago about alloy blocks being cast by someone. While an all-alloy engine for my S3 sounds interesting, I’d settle for a ‘new’ standard long-engine.
I ask because most available engines have been rebuilt at least once, if not twice, and the metal does get ‘tired’ after a while.
Wow, that would be something!!
As to the cast iron tiring. Naah. More likely to suffer past machine shop butchery.
Many machinists prefer seasoned blocks as opposed to raw new castings.
The right shop, the right guy and the result will match or even surpass new…
But, the alloy head can be a different matter.
Dare I mention? No I will not.
Carl,
I believe someone is indeed recasting XK blocks: that said, unless you own a few oil wells, ya might wanna sit down for the cost!
Further, for street use, the critical components,; e.g., crank, rods, and block, can, and do, remain perfectly serviceable, after 1-2 rebuilds, if checked properly.
Fazal,
Carl is right, of course. Cast iron won’t tire - different from magnesium housings. Unless there are cracks there is no need to replace
Jaguar tried to cast the XL block in aluminum for the lightweight E-types, but it was a complete failure as the blocks warped.
That being said I’m sure modern design could make it possible, but at which price? Curious to learn.
Jochen
75 XJ6L 4.2 auto (UK spec)
Jochen
Good to hear from you Fazal,
Eagle offer a 4.7l alloy block. I don’t know if there’s just one foundry or more, but I have seen the price. Hugely expensive… naturally.
Jaguar re-cast some aluminium blocks for the Lightweights…
https://crosthwaiteandgardiner.com/parts/jaguar/cylinder-block-in-alloy-wet-sump
@Jochen_Glockner, 12.840,00… Pounds! With 15k Euros there are more than enough reasons to keep not only the iron which must be better suited to the XJ anyways (noise, strength,…) while supplies last. Supplies may even last me out.
But it’s beautiful 
1 Like
Learning’s sometimes faster than writing …
When Jaguar cast the XK engine in aluminum they were trying to make good for the E-type’s lost date with racing history … and while there was plenty of time for improvement of the old XK engine left they never continued this route … I 'd just assume they knew why.
So, Fazal, you might better save the bucks for the engine and invest in immersive decoating and cataphoretic painting instead for the next 50 years to come - your block won’t be the problem …
Good luck
Jochen
75 XJ6L 4.2 auto (UK spec)
Amazed that for that price, it doesnt incorporate a one-piece main bearing saddle.
Your point is dead-on, though: this may not be an “improvement” for street use.
As I understand it, the LWE blocks failed because of the very heavy ZF 5-speed boxes. Not only were they heavy but also long, which caused a cantilever effect putting pressure inwards at the rear of the block wall. That unsupported water jacket wall area was never designed to resist heavy crush pressure by the top of the bell housing as the engine/gearbox ‘sagged’ under racing loads, even with extra bracing around the bulkhead stabiliser mount.
The few alloy block engines made earlier for Ds (which use a six-point mounting arrangement) never had that problem. I.e. they had different reasons for failing! 
The obvious question should be why they used cast iron in production… I’m coming from the assumption that aluminium (although in theory more expensive) was in surplus after the war (hence the Land Rover’s aluminium shell) and steel expensive. With sufficient strengthening surely a good idea? They’ve proven that the alloy block can work and is strong enough for racing. Is it a casting issue, or does it have to do with strength to weight, noise, technology,…? The later past-xk engines were fine with alloy blocks. Lack of development time?
Hard to read the cards … Maybe just a combination of adverse circumstances: during the phase of development the post-war excess supply of aluminum was hard to anticipate. Then aluminum was considerably more expensive than steel and steel was state of the art. Even BMW’s M30 inline six had a steel block. Then they may have thought that their own all-alloy 12 cylinder plant was going to replace the XK engine altogether - and then money was scarce and the AJ6 may have appeared at the horizon.
Anyway an all-alloy engine in 1975 saving some 100 kg, giving the XJ some extra pep and mileage might have made a big difference …
Good luck
Jochen
75 XJ6L 4.2 auto (UK spec)
Actually the first sixes (AJ6 3.6) were apparently noticeably rough and unrefined compared to the XK engine. Casting wasn’t an issue but iron (not steel) blocks damp the noise better and the extra block
mass improved the sprung/unsprung mass ratio and therefore the ride.
Cheers, David. It’s been a while since I’ve got on to JL (or played with my Jags, actually).
The consensus appears to be that my fears are unfounded so a rebuild is on the cards.
Thanks everyone, for the feedback.
1 Like
Makes sense. Iron is stronger, less noisy and less troublesome… also the head is smaller and it seems worthwhile to design the head in aluminium (as on my `00 bmw and tons of older cars).
I‘d never consider the aluminium block for the money. Any XJ worth the money either already has an aluminium V12 or should stay original.
For racing, sure. Supplies will be plenty for at least 30 years, as the number of owners goes down.