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Re: RtTorquing Head Gaskets

To: "'FOT'" <>
Subject: Re: RtTorquing Head Gaskets
From: "Timothy F. Murphy" <>
Date: Sat, 15 Feb 2003 20:31:35 -0600
    I have been following this thread with interest.  Quite a few years
ago, when I was a member of a manufacturing consortium for my company, I
attended a meeting at the Univ. of Mich. in Ann Arbor.  I got into a
discussion on torquing bolts for automotive applications with another
member who worked for a company who sold assembly equipment to the auto
companys.  He said they almost always set the machines up to torque the
fasteners to a set point to just get tension on the bolt and then the
final torque was done by moving the fastener through a specified angle.
The actual torque might vary but the clamping force would be very
consistent.  I believe this is also what Bill Babcock related.
    In the same line, a number of years ago I rebuilt the cylinder head
on my Mercedes 6 cylinder engine; cast iron block, aluminum cylinder
head.  The Mercedes workshop manual first said to inspect the cylinder
head bolts for a maximum length and if they exceeded that (stretched too
far) they should be replaced.  (Pretty hard to do on our TRactor engines
unless the distance from the top of the deck is used.)  The tightening
procedure for the Mercedes was three step: first, torque to 70 Nm;
second, 90 degree of rotation; third; another 90 degree rotation.  It
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.
    The only source I've ever seen that gave the adjustment or
compensation to dry torque for bolts is the "Pocket Reference" by Thomas
J. Glover (I got mine from Griot's Garage).  The dry torque is to be
decreased anywhere from 34% for plated and cleaned bolts to 55% for
graphite and oil lubricated bolts.  Unfortunately, anti-sieze isn't
listed.  The closest thing is probably "White grease" for which the
reduction is to be 45%.  The "Pocket Reference" gives the dry torques
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.
    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.
    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?
    Thanks for the info on taking the trunions apart.  They look pretty
good as does the threaded end of the vertical link.  I just finished
bead blasting all of the parts and can start painting them.  Thanks also
for the info on the bushings.  I think I'll just use what I have. They
are either nylon or delron and are in very good condition.  If I had
access to a durometer maybe I could figure out what I have.  Everything
fits nice and snug.  The bushings that go onto the upper inner fulcrum
for the upper A-arm are eccentric to allow for some camber adjustment.
They were set for maximum negative camber.

Tim Murphy
Making progress on TR-4 CT511

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