I like the bolts I get from Aircraft Spruce and other aviation suppliers.
ARP is great for critical stuff, but too expensive otherwise. We have a
local company called Tacoma Bolt that handles all kinds of fasteners and
they have a certification program.
There are actually a lot of car and motorcycle manufacturers that use bolt
stretch or rotation as their spec. I recall that VW rabbits rod and head
bolts are single use, stretch to torque bolts. Kawasaki motorcycle engines
use stretch as the spec for the rod bolts--I just finished rebuilding one
for my Radical.
The ARP site has a lot of technical information about properly torquing
their bolts--stretch is the preferred method. It's always a challenge with
a blind bolt. The bolts that hold down the top of the pressure vessel on
some nuclear power plants are heated during torquing and are hollow so
they can have their stretch measured. Maybe that what we need--hollow head
There is also a technique using ultrasonic transducers for measuring
stretch. It's actually reasonably inexpensive. I might investigate it as
an alternative. Not that I'm getting all anal about this...
From: stutzman [mailto:email@example.com]
Sent: Saturday, February 15, 2003 7:47 PM
To: Timothy F. Murphy
Subject: Re: RtTorquing Head Gaskets
carroll smith in his book "nuts, bolts, etc" said never buy a nut or bolt
that was made in asia. a lot of the hardware store stuff comes from
there. look for U.S. made grade 5. new unused nylocs work well as long as
they are not used where too much heat can soften the nylon, temperatures
above 250 degrees f. bruce
----- Original Message -----
From: "Timothy F. Murphy" <firstname.lastname@example.org>
To: "'FOT'" <email@example.com>
Sent: Saturday, February 15, 2003 9:31 PM
Subject: Re: RtTorquing Head Gaskets
> 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