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Re: RtTorquing Head Gaskets

To: "Timothy F. Murphy" <>
Subject: Re: RtTorquing Head Gaskets
Date: Sat, 15 Feb 2003 21:06:54 -0700
Timothy F. Murphy writes: 

> also said to oil the thread of the bolt and the contact surface.  That's
> about the only workshop manual that I've seen that gave specific
> instructions and used angle of rotation.  It's consistent with what Bill
> said and what the guy in Ann Arbor told me.  It also makes sense.

Some Chrysler products also use the same method. It's very simple in 
principle. If you know the torque required to crush the gasket, pull up all 
the threads, etc., then the angle gives a certain amount of thread, which is 
also predictable. One-half turn on a 1.5mm pitch gives you 0.75mm of preload 
on the fastener, etc. 

> for coarse thread bolts and says to increase the ratings by 9% for fine
> thread bolts.  I'm not sure I understand that.  With a fine thread the
> same torque would give higher force.

When they say increase rating, they mean the allowable torque is that much 
more. Fine threads have more surface area than coarse threads and can stand 
more torque. 

>     While on the subject of torque and fasteners, I am looking for some
> missing torque specification pages from my Triumph TR-4 Workshop
> manual.  I am missing pages 9, 10, 11 and 12.  Page 13 is the last page
> of the "Nut Tightening Torques".  If anyone has the workshop manual and
> has these pages I sure would appreciate a copy of them.

My factory manual is a bit water-damaged. Don't know if those pages are 
legible. If they are, I can scan them in when I get home (at work right now) 
and send you a pdf. 

>     I plan to replace most of the fasteners on the TR-4, especially
> critical ones such as suspension.  I am very suspect of much of the
> standard hardware that can be purchased at places like Home Depot or
> Menard's.  We have a Fastenal in town and also a True Value hardware
> store which has a very good stock of hardware.  Any suggestions as to
> who to trust?  All grade 8's ain't neccessarily grade 8!!  I've noticed
> that most of what looks like original hardware on the TR-4 is grade 5.
> Lastly, what is the thinking on the use of the NyLok type of locknuts
> for racing application?

If you want to be sure the nut doesn't back off, use a deformed head 
prevailing torque nut. Nylocs are okay, but I still worry about them backing 
off if they loosen up. Only problem with the deformed head PT nut is that 
you pretty much have to throw the bolt away along with the nut after 
removal. If you want to extra sure the nut can't come loose, drill and 
safety wire. 

I'd go with Fastenal, but any store that can say with some authority that 
they comply with the National Hardware Standardization Act and knows the 
details of that is likely going to supply you with the correct hardware. 


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