Cracks between cyl liners - is it an issue?

XK-Engine
1

Being new to the world of the XKE (my first Jaguar restoration) I really need your collective wisdom on a problem I have please,

My machine shop has told me that the (4.2L) block has a couple of cracks BETWEEN two cylinder liners parallel to the side of the block. He was unable to advise me if it is a non issue, or, if the block is toast.

Not that I know much about this stuff, my thought is there are cylinder liners that compress via the head gasket to the head. Should any water creep up to the surface it is trapped by the head gasket.

Having to get a “new” block would be a big blow to me, in a few ways. In a perfect world, another block is best, I understand that… .but is it REALLY necessary?
Thanks all< Pat

2

Hi Pat, we have a 4.2l in the good lady wife’s XJ6. It was laid up for a long time before recommissioning last year - the attached was part of my pre-reading. Others will comment on validity - it’s a reprint from the “Jaguar Enthusiast” magazine. Proposes “top-hat” liners as the ultimate fix. Should start a discussion for you if nothing else! Paul
http://www.jagtas.org.au/torque/techtorque/fighting-the-flaw-in-the-4-2-engine-block/

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I’ll move this to the #xk-engine category.

4

Any crack is an issue, it will run ok, but you will always wonder for how long…if the bores are well worn, reliner, but !! get some good advice as there is a set tolerance for these liners, and the material they bed into is also critical, Richard Olsen on your shores knows the quality of machining required, Rob Beere over here, then a set of ARP bolts and decent pistons equals plenty of trouble free motoring…

5

Greetings All,

I don’t doubt that the “top hat” works, but unless my understanding is wrong, how would you resurface the block in the future?

Meanwhile, for years, diesels, which operate at a far higher compression ratio than any Jaguar, have been using a different technique.

That technique is a “fire ring”. A groove cut in the top flange of each liner.
The groove is one half the depth of the ring. The protruding depth of the ring add extra force/pressure to the gasket effectively sealing it from any issues.

I’ll agree top hatting will work, but what do you do in the future, machine around the liners or replace them?

See enclosed picture.

IMG_0597.JPG1600Ă—1200 279 KB

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The liners finish flush - and may even be a machined finish? Don’t expect that a future decking of a few thou would be a problem? Paul

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I must be missing something, I’ll go check the link out again.

8

It also says start with a perfect untracked block. Isn’t that what you are trying to overcome?

The ring seals the individual combustion chambers from any water that may emanate from the crack.

Or did I miss something?

9

You got me curious, as I am no expert on engine rebuilding

however the local Jag mechanic who owns a machine shop tophat liners them, and the deck is machined

although I havent asked him, I cannot see why they could not be skimmed again later if needed

liners also restore the original bore, and attend bore wear which would be prevalent in this age engine

I did some googling on fire rings and this link has some detailed technical discussion on the topic

https://www.dieseltruckresource.com/forums/3rd-gen-high-performance-accessories-5-9l-only-107/what-fire-ring-239781/

is there anyone known to had an XK engine fire-ringed or o-ringed ?

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The fire ring method has been used in a couple of my engines but I do not race.

I’m aware of other that use it that do race.

As of late, this top hat method is being bandied about for the last year or so.

I coulld have this wrong, so bear with me…

The cracking occurs between the cylinders in the small web between. This problem became more critical as the displacement increased over the years.

The XK started as 3.4 and progressed to 3.8 liters and finally progressed to 4.2 liters. The difference? The 4.2 is a wet liner motor whereas the previous displacements were dryliner example.

Wetliner, means cooling water actually touches the liner. Dryliner examples have cast iron surrounding all the cylinder liner.

It’s because of the increasing liner size that there is less metal between those liners.

Now, that means the outer diameter of the cylinder liner flange has increased.
Machining a flat between two liners means you have to utilize the space between the liners to machine that flat surface on each liner for them to mate and seal.

The cracks usually show up on the perimeter of the liner, about an 1" I see usually involved.

How machining a flat which will not address ALL of that 1" is a mystery to me.

Then there is the part of the article that says use a “perfect” block…which then goes on to talk about how “just because you don’t see any cracks, they can exist beneath the surface”!

I don’t have have any pictures of the fire ring install other than the pic I included.

I do have a couple of blocks in my workshop, one of which has some cracks. I will attempt to unearth it and snap a couple of pics, possibly tonight after work.

11

Timely topic. My engine is with my rebuilder and I took the attached picture over the weekend. My block had a crack between cylinders 5 and 6…the two at the front of the engine. The picture shows the block after top hat liners were installed in these two cylinders and the deck was skimmed. Looking from below you can see that they are sleeved (liners are a bit thicker)…but for above you can’t tell at all since the top hats are machined into the surface.

wp_ss_20170612_0001.jpg1440Ă—2560 592 KB

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This is all really interesting to me as I started the thead. But I have to
pose the question again, that Lovell asked is in order to Top Hat the
article says to start with a block crack free! Mine is cracked…

So simply put, does using the Top Hat method (or perhaps Ring of fire) make
my block usable again for daily driving, not racing?

This is what I REALLY need to know please.
Thanks, pat

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In my case top hat liners will be sufficient…else I’m dropping a lot of cash for no reason. Not having seen your block I don’t know for sure, but my understanding is this is a common XK engine issue and top hat liners are the fix. The shop I’m using has a good reputation…so no reason to doubt their judgment.

Tom

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A few “fire ringed” 5litre XK engines in the UK running with “Wills” o rings, and twin plug heads …

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from talking to the Jag engine rebuilder, who has been doing it 30+ yrs, and his father before

its the common problem of short cracks between the close cyls that mean the gasket will not hold that is solved by the tophats…if longer cracks exist, I would presume they would be worked by the other methods mentioned of drilling and plugging…how would fire-rings address longer cracks?

do the fire-ring engines need special gasket?

you would still be up for the cost of machining the groove and bore, repair cracks etc

the cost quoted to me to machine and install tophats was ~US $900

I think you would be very fortunate to find a block that was not cracked and did not need bore work

the best are supposedly the 65-68 short stud blocks, I have one but it is seized

I do not understand what is the situation with the depth of cracks, other than when I asked I was told it was not an issue with tophats installed

read an article saying that it can be problematical if the installer does not do the job exactly right…think it is an online article from the liner suppliers

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Greetings All,

Will get out to shop for pictures tomorrow. Work drained me and the 95F heat didn’t make me anymore ambitious after work.

I understand that they are using the flange to seal rather than the the “web” of cast iron in between the existing liners.

Not sure if longer cracks COULD be addressed. They would likely exist between the cylinder liners and I don’t see how there would be access?

I’ve had a couple of liners removed. They were machined out. It was deemed safer because of fear of damaging the thin material between. It’s also a good idea to work one cylinder at a time as you risk damaging that area?

With regards to the cracks, if you have sealed the combustion areas from coolant ingress, the cracks are irrelevant at that point, aren’t they? You have a crack, but the coolant isn’t going anywhere it shouldn’t.

Here’s one to cogitate on…

Jaguar used the same basic block for almost 45 years, obviously, with displacement changes, all the time that cylinder spacing was increasing to stretch the limits of what would fit between the bearing journals.

The space is not equal distant between all cylinders.

Compound this with the fact that the head’s combustion chambers do not center perfectly over each cylinder due and the sealing area is diminished even more because of the mismatch.

Roger Bywater/AJ6 Engineering, has written much about the XK engine having been employed by Jaguar during the XK engine production. It’s worth Googling and checking out his site. Read all six pages, especially the last page on uncoupling the block harmonics to keep from amplifying chassis resonance.

He recounts that many of the cooling issue ps manifested themselves in the last iteration of the XK in the 4.2. The wetliner construction being the main culprit as the inconsistent masses of metal that surrounded the liners effected the expansion rates in an uneven manner.

Since I’m most likely going to get out to the shop tomorrow, barring feeling old, any specific shots you looking for? Let me know before lunch time tomorrow.

The general plan…I believe I still have a 3.8, MKIX block with cracks between the bores, I’ll also grab a picture of the head and the mismatch if I can figure out a way to show it, along with a 3.4, 120 block so you can see the spacing difference, along with a fresh rebuild that still has the head off. Anything else, let me know.

As always…if anyone knows of a mid 30’s Standard Flathead Engine for sale…I’m looking for one for my SS1 Tourer.

17

Greetings All,

Managed to get a few pictures…

First, Tony, the gasket used with a fire-ring is the stock gasket, nothing special.

I’m going to go out on a limb and say the block pictured with the 2 top hat machined liners is a 3.8?

Here’s my $.02. I have no doubt it works, it’s a good quality repair.

I do however wonder about if it would work on a 4.2? Here’s why.

Pictured below is an XK120 3.4 block, notice the distance between the cylinders.

IMG_1513.JPG2592Ă—1936 951 KB

Next is a MKIX 3.8, notice the distance between the cylinders.

IMG_1511.JPG2592Ă—1936 986 KB

Compare the 2 distance, as displacement increases, the web between gets smaller.

Unfortunately, I don’t have a 4.2 engine block open at this time, but that web between the cylinders gets even smaller than .3125.

The 3.4 web was .5625 or 9/16". The 3.5 was .3125 or 5/16". The 4.2 is likely to be liners touching, but again, I have no picture, but you get the idea.

` I’m not exactly sure that the outside diameter when machined will span the usual cracking area?

Sorry I didn’t use the same ruler shot on both of the other blocks.

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Tapped, just realized your block looks like a 3.8

Patrick
'66 fhc

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Indeed it is. Good detective work!

Looking forward to getting mine back. Has been over a year at the shop. Shop is in high demand but small and reportedly has 40 engines in backlog at any given time across different brands. Latest rationale for my continued wait is someone with a 12 cylinder Lamborghini engine got prioritized over mine. I suspect they prioritize by who throws the most cash at them. Fortunately I’m in no hurry…so I continue to wait. They are working on it though as I now have evidence. Should have it back later this month. Plenty of other things to work on in meantime :slight_smile:

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Hi Pat I also live in Victoria. Chuck (machine shop) called me about your engine a few days ago. He’s done about 5 XK engines for me over the last ten years or so, most of them modified. The cracks between the cylinders on the later cars are fairly common - I suspect your engine was overheated once to often. I’ve always understood that the cure was to push out the liners and weld the crack, remachine the bore and push a new liner in. Incidentally the liners are dry liners - they are wet in V12’s. I understand that when Jaguar pushed the engine to 4.2l they were worried that the bore casting which was somewhat inconsistent, maybe too thin in spots so it was best to insert a liner. Chuck thought that doing this would be prohibitively expensive. Again as in understand it bores 1, 2, and 3, are siamesed - that is there is a mostly solid web cast between the cylinders top to bottom, similarly with 4, 5, and 6. This makes water circulation around the cylinder somewhat problematical. Jaguar resolved this in the last few years of the XJ6 engine by use of what came to be called a “split” block. They ran a circular saw blade down through the deck into the web, between the cylinders, at 90 degrees to the block length. The permitted coolant to circulate from side to side more effectively. I had one of these blocks in my race car for most years, and it always ran very cool. The cut was open in top - in other words, there appeared to be no structural issues with it - that’s why I’m going on about it.

The problem with the cracks is that if they go into the water jacket, with the liner being very thin there is inadequate sealing surface to keep combustion gasses out of the coolant and coolant out of the combustion chamber. I mean you may get away with it, but with an aluminum head and a cast iron block it’s dodgy.Because the sealing surface is so small I don’t believe that a sealing (fire) ring would help… Using a top hat liner will give you more sealing area. Once installed the top of the block is planed level, so that’s not an issue. Machine shops install liners all the time. It might be worth having the liner removed, to see the damage and installing top hat liners if applicable…