Cylinder head bolt torque, dry threads or lubricated threads?
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Senior Member
Joined: Sep 2013
Posts: 531
Likes: 180
From: NE Ohio, USA
Cylinder head bolt torque, dry threads or lubricated threads?
I have a quick question.
I have looked at old list posts on the XJ40 forum on various Jaguar specialty forums and I have found the following information on cylinder head bolt torque:
“The cylinder head must be torque tightened as follows:
Following the sequence shown in Fig 1, tighten the cylinder
head bolts to 59 - 61 Nm.
NOTE: Ensure that the camshaft is still on TDC using the
service Tool 18G1433 (Fig 2).
Then rotate the bolts clockwise in sequence through exactly
90 degrees using Special Tool LST122 or a self-manufactured
tool of the dimensions given in Fig 3.”
What I am wondering is if these torque specifications are for dry bolts and threads (in the block) or if this is a lubricated thread value.
I.E. should I be putting oil or some other lubricant on the threads of the cylinder head bolts prior to torquing them down or not?
I have looked at old list posts on the XJ40 forum on various Jaguar specialty forums and I have found the following information on cylinder head bolt torque:
“The cylinder head must be torque tightened as follows:
Following the sequence shown in Fig 1, tighten the cylinder
head bolts to 59 - 61 Nm.
NOTE: Ensure that the camshaft is still on TDC using the
service Tool 18G1433 (Fig 2).
Then rotate the bolts clockwise in sequence through exactly
90 degrees using Special Tool LST122 or a self-manufactured
tool of the dimensions given in Fig 3.”
What I am wondering is if these torque specifications are for dry bolts and threads (in the block) or if this is a lubricated thread value.
I.E. should I be putting oil or some other lubricant on the threads of the cylinder head bolts prior to torquing them down or not?
Joined: Dec 2009
Posts: 13,684
Likes: 9,627
From: Wise County,TX
Jaguar authorized the reuse of cylinder head bolts as mentioned in TSB 12-62am.
"ACTION:
Before reusing a cylinder head bolt, clean the threads thoroughly.
After reinstalling and fully tightening a used cylinder head bolt (EXCEPT when a
NEW bolt has been installed), mark the bolt head with ONE punch mark, using an
AUTOMATIC center-punch."
It would seem that a dry clean thread is recommended.
bob
"ACTION:
Before reusing a cylinder head bolt, clean the threads thoroughly.
After reinstalling and fully tightening a used cylinder head bolt (EXCEPT when a
NEW bolt has been installed), mark the bolt head with ONE punch mark, using an
AUTOMATIC center-punch."
It would seem that a dry clean thread is recommended.
bob
Veteran Member
Joined: Jun 2015
Posts: 1,514
Likes: 687
From: Florida
The torque specs TTY bolts are normally for dry bolts and threads.
However, when I did my cylinder head I sprayed a light coat of silicone lube( which has the viscosity of water) on the bolt threads prior to installation and no harm was done.
Just make sure that there is no residual liquid in the bolt holes. Use compressed air to clean the bolt holes.
Others will chime in shortly.
However, when I did my cylinder head I sprayed a light coat of silicone lube( which has the viscosity of water) on the bolt threads prior to installation and no harm was done.
Just make sure that there is no residual liquid in the bolt holes. Use compressed air to clean the bolt holes.
Others will chime in shortly.
Joined: Feb 2014
Posts: 20,492
Likes: 15,273
From: Crossroads of America
Hi Steve,
My understanding is that all torque specifications are based on fasteners that are clean and dry unless otherwise noted in the documentation. Any form of lubrication can lead to over-torquing a fastener since friction and the tensile strength of the fastener are fundamental aspects of torque (rotational force). When a substance such as threadlocker or anti-seize compound is specified, the torque specification takes into account the lubricity of the specified substance. So no lubricant or other substance should be applied unless specified in factory documentation or when the original fasteners show evidence of threadlocker.
Cheers,
Don
My understanding is that all torque specifications are based on fasteners that are clean and dry unless otherwise noted in the documentation. Any form of lubrication can lead to over-torquing a fastener since friction and the tensile strength of the fastener are fundamental aspects of torque (rotational force). When a substance such as threadlocker or anti-seize compound is specified, the torque specification takes into account the lubricity of the specified substance. So no lubricant or other substance should be applied unless specified in factory documentation or when the original fasteners show evidence of threadlocker.
Cheers,
Don
Last edited by Don B; Jul 2, 2019 at 10:12 PM.
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