The head does not have slots. The slots are only in the block and are closed by the head gasket. Or should I say, they are supposed to be closed by the head gasket but that seems to be where I am having the problem.
The engine number is 8L82561/H. The number is lower than the one in Kevin’s post where he mentions the part numbers changed at 8L89109. However, it is not beyond the realms of possibility that the engine number has been changed to suit a previous owner’s purposes! In Thailand, imported cars are subjected to ridiculously high import duty (up to 320% for cars with large engines). So sometimes a car might be brought in and given the identity of an existing car that has come to the end of its useful life.
There is a casting number on the LH side of the block P41300F
Completely off track, Frank. You can’t mix up a 4.2 XK gasket. I had to make that gasket in the picture fit as it was slightly too long (as you can see in the picture). The bores fit fine though.
And old trick: wipe cylinders or decks of blocks, cylinder heads and shafts etc with dirty aka oil contaminated petrol (gas) with a rag. You will immediately see a lot more, even on polished nice surfaces.
Yes, that is the typical 4.2L block craked between bores, I also have a spare engine like that, it was in the 1975 XJ6C when I bought it, not original to the car.
I don’t believe I have seen an XJ 4.2 block that wasn’t cracked between at least 2 bores and was under the impression, perhaps incorrectly, that that was why the slotted block was introduced, not for additional cooling. It’s also why many engine rebuilders won’t touch one unless the can fit "top hat "liners. To the problem in hand, is it caused by the head not having slots to match the block? If the coolant in this area had smooth passage would it not try to escape through the gasket, or perhaps is causing a localised hotspot and warping?
The OP informed us his block does not have liners fitted, which was news to me, as I know the S1 XJ6 and earlier 4.2 have a liner fitted, but we learn on this forum
The head, block and gasket dont line up on 4.2L motors (to the best of my knowledge
I would obtain the home magnaflux/crack test kit, its not expensive
I have done quite a lot of reading up on the 4.2 block and they way I understand it is that Jaguar recognised there was a problem with blocks cracking between the cylinders with the 7L version. They determined that the main reason was inadequate circulation of coolant across the block. I found this description:
They crack because of the very high temperature differentials created by inefficient coolant circulation. Coolant can circulate around the block only at the very front and the very back. The water pump outlet is positioned so that when the thermostat first opens, super cooled fluid is pumped mainly down the exhaust side of the block. The inlet side with its much less efficient circulation, remains closer to the thermostat temperature. This means that you could possibly have 0 degrees C fluid entering the exhaust side of the block and 88 degrees C fluid (fuel injected cars) leaving the inlet side. The cooling fluid then passes up through the cylinder head mainly from the exhaust side, passing out through the inlet manifold, again maintaining the temperature differential on the inlet side of the block. This problem was actually solved in 1981 by machining latitudinal slots across the block and so fluid was able to circulate from the exhaust to the inlet side between the bores, equalising the temperature in this weak area. Unfortunately this gives you only about 0.118 inch (3mm) for the gasket to seal on between the waterways and the combustion chamber.
The slotted block version does not have liners. The slots are deigned to be sealed by the head gasket and coolant flow to the head is via the other passageways, same as the earlier version of the engine.
So you are saying the coolant does not flow into the head via the slot, but merely connects the 2 sides of the block? Therefore no need for a slot in the head gasket? Sounds like the setup the OP has.
Still, David - his gasket doesn’t seem to fit; it’s easier to cut a too long sausage than to add to too short one…
All bore/distance measurements should of course match that of the gasket - and he should verify that… And as an aside; the gasket should also fit the head, to make good sealing - we seldom check that unless we are replacing heads. And some heads will ‘fit’ - even if wrong. As he says, odd things may be done in Thailand…
The chamber spacing never changed,only the rear passages - unless there is severe corrosion the head will seal - as long as the steel part of the gasket fits the bores the block is junk and always was, but it may just work with a different gasket…
You cannot cut away much from a too long gasket, that won’t work.
Looking at Andy’s close up picture of the offending area, David - I doubt if any gasket will seal properly?
If water leaks into the cylinder in this area, it also means that it’s subjected to the high pressure and heat from combustion. Which over time will erode the thin block material, as it seems to have - to me the offset of the slot implies that the block should never have left the factory…
A straightedge might (will?) reveal a gap under any(?) gasket. What about welding up the slot, with all the drawbacks that entails - and somehow smoothing the weld to block level? Or just accept that the block is indeed junk…
On it. One bore seems t be slight;y off. Not enough steel fr a gasket to seal. it will never work as it nw is. Teh dd metal was a decent effort to rovide enough meat beteeen the bores to get a seal
I see the slot as a means f stping a crack something like an age test method of two sall holes at the end of each crack to stop it drm traveling. A for os stress relef
In my view there s only a coule of possiblem ways to save that block.
I would very much like to hear from someone that has actually seen a slotted block first hand, and hear how they got on with head gaskets. I can only find one other photograph on the internet of a slotted block:
This block clearly also has the slots offset and in this case the land between cylinder 2 and the slot inbetween 2 & 1 looks extremely small. So that shows that these blocks came out the factory like this.
I am still hoping that the Cometic gasket will locate accurately and have enough surface to seal the slot. I think the steel of the gasket should deform into the slot creating a seal, and that my last attempts have failed due to poor location of the gasket giving too little surface area at excatly the point where the land on the top of the block is smallest.
You are… nothing special about them…
6 is the cylinder next to the chain. The slots are not centered at the head studs because the 4.2 uses the head developed for the earlier bore spacing.
There are some Utube videos by Adam from Living With a Classic. His XJ6 head gasket failed a few times & he eventually decided it was a fault with the block, so he found a replacement engine.
My engine block looks no worse than this one, the slot between 6 and 5 looks the same as mine with minimal land to the side of bore 5. Were you able to get a seal with the head gasket and run it normally? If so, what brand of gasket did you use?
But a question; I thought your picture, IMG 2647 showed the 5/6 cylinders, and the coolant leak leak into the #5? It’s not so much the narrowness of the metal but that it seems to be eroded to below the surface of the block. In this case, the metal insert of any gasket will not deform to seal…
Again; that coolant leaks into the cylinder here; high temp and pressure gases will also exit the cylinder causing further erosion. Ie, keeping the coolant out of the cylinder is the easy part - keeping the hot gases inside the cylinder requires something solid…
I have also encountered this issue of an ill-fitting reproduction head gasket. In my case it was a modern green-box Lucas brand. It was about 1.5 to 2mm too long so that nothing lined up correctly and the stud holes rubbed against the studs not allowing it to lay down on the block. I believe the reason this happens is because some part of the manufacturing process uses a rotary die - very dependent on proper set-up and speed. Poor quality control.
I saw in a pic earlier on in the thread that you seem to have a similar problem with a gasket you said was sourced through SNGB. It looks okay near the center where everything lines up pretty well and then, as it progresses to the front and back of the block it’s more and more out of whack.
In my case I sourced a New Old-Stock Payen brand and it fit perfectly. Obviously with 8L blocks like yours, a perfectly fitting gasket is essential. I know you mentioned you were in Thailand so not sure if Ebay is a good source but that’s where I found mine. BTW the genuine Payens have a triangular logo printed on them while others I’ve seen (like the POS Lucas I mentioned) don’t
