[pre-xk] Torque cylinder head nuts for 2.5 litre

Does anyone know what the torque for the cylinder head nuts
for my 2.5 litre is?

And is it the right procedure to tighten them when the
engine is cold. Then warm up the engine and tighten them
again. And maybe after some miles tighten them again on the
warm engine?

And what is the right order to tighten them?

I guess that the rocker shaft has to been removed for that?

Thank for any help.

Kind regard
Detlef–
JaguarDriver
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Hi Detlef,

Normal studs 92 lb-ft
Waisted studs 63 lb-ft

Try to imagine the following diagram with the rev counter drive in the
bottom row:

–12—4---14—17—6---10

19—2w–9w–1—8w–3w–18

–11—7---16-o-15—5---13
Rev counter–|

The studs with the w suffix pass through the inlet manifold and have a
waisted centre section hence the lower torque setting.

I would just tighten them cold then recheck 100 miles later.

Peter

JaguarDriver wrote:> Does anyone know what the torque for the cylinder head nuts

for my 2.5 litre is?

Second try…

Hi Detlef,

Normal studs 92 lb-ft
Waisted studs 63 lb-ft

Try to imagine the following diagram with the rev counter drive in the
bottom row:

–12—4---14—17—6---10

19—2w–9w–1—8w–3w–18

–11—7---16-o-15—5---13
Rev counter–|

The studs with the w suffix pass through the inlet manifold and have a
waisted centre section hence the lower torque setting.

I would just tighten them cold then recheck 100 miles later.

Peter

JaguarDriver wrote:> Does anyone know what the torque for the cylinder head nuts

for my 2.5 litre is?

In reply to a message from Peter Scott sent Sun 18 May 2014:

Hi Peter,

perfect!!!

Thanks a lot.

Do you know the torque f�r the nuts of the rocker shaft?

All the best
Detlef–
JaguarDriver
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Hi Detlef,

Sorry. I’ve never seen figures for those. My source for the head studs
was the Mark V manual which is much more comprehensive than the MkIV one.

I think you’ll need to refer to general torque guides for mild steel
bolts such as:

They aren’t that critical. Just make sure the nuts have spring washers
and use your own judgement on tightness.

Regards,

Peter

JaguarDriver wrote:> In reply to a message from Peter Scott sent Sun 18 May 2014:

Hi Peter,

perfect!!!

Thanks a lot.

Do you know the torque f�r the nuts of the rocker shaft?

All the best
Detlef

In reply to a message from JaguarDriver sent Sun 18 May 2014:

pose by definition you have to initially tighten them when
cold.
But then we warm the engine and re-tension them.

When re-tensioning them ech nut should be undone and then
re-tensioned.

It is also important to make sure the dome nuts aren’t
bottoming in the threads if the haed or block have been
faced. And the nuts with the alloy caps go over the inlet
tract.

We also check them again after about 500 miles , and it is
annoying to have to remove the rocker shaft but … : >(

Make sure when replacing the head that no carbon from the
inlet tract drops down onto the head gasket.

Easy to happen, which is why we remove the core plugs and
clean the tract out with a wire brush and have the head
tanked.–
Ed Nantes SS
Melbourne, Australia
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In reply to a message from Ed Nantes sent Sun 18 May 2014:

Hello Detlef, another consideration on dome nuts bottoming
in the threads comes from variation in dome nut
construction. There are dome nuts which are too short in the
internal thread cut depth. While a bottomed-out dome nut
might still provide sufficient gasket compression in some
circumstances, I am more comfortable using the full design
thread engagement length when securing.

Torque for 2 1/2 liter engine head bolts is given on Page
B.37 in the Mark V service manual as 1100 pounds-inches for
1/2’’ BSF bolts and 750 pounds-inches for waisted bolts (and
also the 7/16’’ BSF 3 1/2 liter bolts). A recommended
tightening pattern is on Page B.27 in Plate B.21. I
calculate 1100 pounds-inches as 92 pound-feet and 750
pounds-inches as 62.5 pound-feet. My experience is that on
the 3 1/2 engine 62.5 pound-feet work fine on gaskets
sourced via the Nantes brothers’ reliable methods and
suppliers. For any, new or used, head bolt utilized it is
worth assuring you stay in the elastic range of bolt stretch
and use a gasket design which does not encourage block
surface distortion.–
Roger McWilliams
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In reply to a message from Roger McWilliams sent Mon 19 May 2014:

Thanks for the info�s and reference. I didn�t find anything
in the MK IV data and obmit to look in the MK V documents.

After dismantling and assembling the rocker shaft, do I have
to check the valve clearance again?

All the best
Detlef–
JaguarDriver
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Yes, you really should check them again.

Peter

JaguarDriver wrote:>

After dismantling and assembling the rocker shaft, do I have
to check the valve clearance again?

Noted that this is a very old thread, I have a 1.5 litre car that has blown a head gasket. The question I wanted to ask was: Are head bolt torque settings for the 1.5L engine the same as the 2.5L engine.

Thanks
Sol.

Unlike the 2.5 litre all the 1.5 litre studs get tightened to 1100 lb-inches.

Peter

Many thanks Peter. Love all your SS videos on U-tube.

Regards

Sol.

Oops! Some of them are embarrassing.

Peter.

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