And I disagree. The cam cover screws are too short to provide sufficient stretch to maintain tension. I recommend a flat washer and a split washer based on experience; too many people have had those cam covers start leaking shortly after reassembly. And it’s difficult to retorque the screws with the intake manifolds in place. Split washers are even more important if you’re using the recommended procedure of installing new OEM rubber half moon seals and omitting the cam cover gaskets altogether and sealing that joint with Loctite 518 or similar.
I have not attempted to install the covers without the gaskets so I haven’t seen the problem as you describe. If lock washers are added when using a gasket, be mindful their added thickness will reduce thread engagement. I used new gaskets (from RockAuto, not claimed to be Gortex but they weren’t paper) and aluminum half moons from Jonas (John_John1) with 518 sealant. No leaks.
Which is why I recommend getting screws one size longer than OEM. There’s no bottom to the holes, longer screws give more thread engagement – nice since the OEM screws had that stupid triangulated thread that boogers up the threads in the tappet block.
The use of a gasket with the aluminum half moon seals is the ideal, even better than rubber half moon seals with no gasket. Neither arrangement will leak any time soon. The only reason the latter setup will ever leak is that those rubber half moon seals don’t last forever, eventually they harden and crumble.
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How about aluminium half moon seals and loctite 518. That’s what I used. No leaks after 2000 kilometres. Actually I used sealant on all gaskets except the water pump gasket because it was part of a belt drive alignment and head and inlet manifold. Everything else was sealant.
Only issue I had was the bolts in the sump which go thru the sandwich plate…maybe 7 of them??
They leaked so I had to apply sealant to the threads courtesy of info in “The Book”.
No leaks…but possibly early days…
…
I’ve got aluminium half moons and gaskets (rubery kind) , and plan to add the split rings and washers
so should be similar to “itasnorust”
I’ve been wondering if the bolts could have already been changed, as there are a few threads out at the bottom. I measured them at 30mm
You mean with no gasket? That depends on the precision machining of the aluminum half moon seal. If it’s perfect, the top of the half moon will be flush with the tappet block and sealing it all up with Loctite 518 will work great. If the machining is a bit less than perfect, the top of the half moon may be a bit higher or lower than the tappet block. Hence, when bolted up the cam cover will be firmly against one or the other and held a bit off the other. Then whether or not the Loctite 518 seals reliably may depend on just how large the gap is. I believe there’s a spec on what size gap Loctite 518 will fill.
If the half moon is too far off, perhaps some other type of sealant would work better. Perhaps Ultra Black; that probably would seal a wider gap. And hey, even the gortex gasket has a limit to how big a step between tappet block and aluminum half moon it can accommodate.
The one thing that will not work reliably is trying to compress a gasket between the cam cover and the soft rubber half moon seal. That’s a recipe for leakage, and apparently Jaguar eventually realized it because the newer engines come with aluminum half moon seals.
If it had been serviced at a Jaguar dealer, they may have been changed; I believe the new ones are gold colored (and very expensive, as they are genuine Jaguar parts). However, I was unaware they were any longer than the originals.
I really like alloy socket head screws for this job. Getting a wrench in there later to retighten those screws would be a PITA regardless of head type, but I suspect allen heads would be the easiest.
Remember that up through 1983 those screws were 1/4"-20, and from 1984-on (I think) they are 6mm metric.
Hey, I just looked it up in my own book! The original screws were 25mm. Your 30mm screws are in fact longer than original.
my car being a 1993.5 , the bolts are M6 (and I’ve got a full bag of 1/4x20 and 5/16 washers that I bought before checking)
I asked about a possible change as I could see 3 or 4 threads out at the bottom :
the bolts are silver grey, with hex flanged head : not the fancy yellow ones,
I found a place offering various socket head M6x35 in several materials: silver zinc steel,yellow zinc, stainless, black 8.8 or 12.9…
I was surprised that the silver zinc is much more expensive than stainless : I’ll check the yellow ones
and as 35mm are more expensive than 30 or 40mm (probably as less common) I may keep the 30mm length : I need to check the thickness of the washers (1.6mm iirc, and split ring)
Not if your half moon seals were equipped with o ring seals…the o ring on which was trimmed flush with the top surface of the bottom cam carrier…so no longer an “O”…and the half moon seal was slightly compressed into position by the cam cover.
Sorted…
Have you tried installing such an assembly? Because that’s exactly the way I designed the original aluminum half moon seal, complete with an O-ring groove, and someone generously fabbed me a set which I tried to install. I made several attempts but I could not get that half moon to stay in place while I installed the cam cover. I gave up, removed the half an O-ring, added the Loctite 518, and never had a leak again. Then I went and changed the design in the Book to omit that O-ring groove.
Even if you could assemble the aluminum half moon with a half an O-ring, that still wouldn’t necessarily make assembly with no gasket a good plan. The half moon could still sit too tall and obstruct the seating of the cam cover on the tappet block. One might be tempted to err on the low side with the machining so that you’re relying upon the O-ring to hold the aluminum half moon up against the cam cover, but I wouldn’t.
Yep. Trimmed the o ring little by little applying a straight edge each time. Stopped when there was a little bit of “crush” required to apply the flat edge. At that amount the o ring would withstand waaaay more pressure than required to hold the oil inside. Then apply the loctite everywhere and fasten down lightly. Couple of hours later torque to setting.
Not difficult and seems to have worked.
while we’re at the cover bolts, anything special on the frton big ones ?
just clean and refit ?
The acorn nuts? On earlier cars these had copper sealing washers under them. I think Jaguar eventually figured out they wouldn’t leak anyway and did away with the copper washers – but kept the acorn nuts because they’re pretty. If you wanna make sure they’re sealed, either install new copper washers or file the old ones flat and anneal them.
on my car, they are standard flanged nuts, nothing fancy or shiny
Jaguar saved the cost of the acorn nuts then! It’s OK, the bottom end of that stud has a gasket that surrounds it (or a loop of Loctite 518 if you applied it correctly) so no leakage can happen there. I’d still suggest a flat washer as always when tightening a nut or bolt onto aluminum. You don’t need a lock washer because the stud is plenty long to provide some stretch when tightening. Besides, if it ever worked loose, it’d be easy to retighten.
Or you could drop by a Harley Davidson dealer and select some nice acorn nuts to fit.
for some reason I thought the bigger nuts were M8, but they’re M7 , so limited choice for acorn nuts (if any) ; no big deal, they can stay. Could Nylock be of any use instead ?
Yes…the washer is a good idea…but what is the relevance of the bolt stretch and remaining tight. These bolts are used for their tension they apply to the sealing surface. The torque setting applies a predetermined tension regardless of length of bolt…and this tension clamps the nut and washer to the surfaces being clamped …and this clamping force and the coefficient of friction do the rest…if there is not a lot of tension then a lock washer or some other device is needed to stop rotation of the nut…
Don’t know why. They’re not prone to coming loose.
Ooooh, I forgot that later cars went metric here. My '83 was SAE fine thread, the same threads that are all over Harley Davidsons.