Torque Specs
Thread Starter
Melting Slicks
Joined: Apr 2002
Posts: 2,337
Likes: 14
From: Norfolk VA
Torque Specs
Hello all. When torqueing a bolt to a specification, it is said it should be done in three stages. For example if a torque spec for a bolt is 80 lbs/ft. Which stages are the proper way to torque a bolt to proper specs?
Increase torque until you reach 80 lbs/ft: 10, 20, 50=80
Increase torque with 80 as the final stage: 20, 40, 80
Increase torque until you reach 80 lbs/ft: 10, 20, 50=80
Increase torque with 80 as the final stage: 20, 40, 80
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
Loaded question as it depends on whether or not you are torqueing a single bolt by itself...for which one pull to maximum is all that is required....or if you are torqueing multiple related fasteners that have a pattern to torque them in a sequence.....like a cylinder head.
On a head......torque to 1/2 the spec., run the pattern....then go around again to 100% of spec.
There is no advantage to torqueing a bolt to a partial specification....then going back and increasing it......
Torqueing in steps is done to keep the mating surfaces from warping during clamping......
For example.....the oil pump fastener bolt.....torque to 100% of specification.
Jebby
On a head......torque to 1/2 the spec., run the pattern....then go around again to 100% of spec.
There is no advantage to torqueing a bolt to a partial specification....then going back and increasing it......
Torqueing in steps is done to keep the mating surfaces from warping during clamping......
For example.....the oil pump fastener bolt.....torque to 100% of specification.
Jebby
Burning Brakes
Joined: Dec 2005
Posts: 1,164
Likes: 224
From: Pawleys Island, SC
More importantly, are you adjusting the applied torque to account for any lube on the bolt? Most of these stated torques are for a dry bolt, unless otherwise specified. Oil or anti-seize lube can result in a 15 - 25% increase in the resulting torque load.
Race Director
Joined: Apr 2009
Posts: 19,294
Likes: 2,754
From: Charlotte NC
IF you apply an oil or anti-seize to the threads of a bolt or nut. The torque value should be adjusted accordingly. And this will this mean that it will take LESS torque.DUB
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
"Staging" bolt torque is only required when a number of bolts are working together to perform some group function....as with an oil pan, a cylinder head, or a water pump installation. If you install each bolt on a stamped-steel oil pan [with 'soft' gasket] separately and at full torque, the pan rail will be so deformed that there is no way it can seal. Likewise, if you do not properly sequence the bolt installation on a cylinder head, you could increase the likelihood that the head gasket will not seal properly.
In these cases, proper sequencing and/or applying the bolt torque in stages are beneficial to the consistency of bolt clamping loads over the entire clamping 'system' those bolts provide as a set. So, it is important to consider the bolt torque "strategy" to be applied when installing bolt groupings.
Where necessary, the GM Service Manuals call out these special needs. So, it is important to research how such installations should be performed, rather than just 'gun the suckers' in with your impact tools.
In these cases, proper sequencing and/or applying the bolt torque in stages are beneficial to the consistency of bolt clamping loads over the entire clamping 'system' those bolts provide as a set. So, it is important to consider the bolt torque "strategy" to be applied when installing bolt groupings.
Where necessary, the GM Service Manuals call out these special needs. So, it is important to research how such installations should be performed, rather than just 'gun the suckers' in with your impact tools.
Last edited by 7T1vette; Nov 11, 2016 at 08:21 PM.
Burning Brakes
Joined: Feb 2000
Posts: 852
Likes: 112
From: Torrance California
This is correct. Only time to apply lube is if its specified. Now I do apply a bit of anti-seize to the face of a lug nut but not to the threads themselves. Doing so could over torque or even snap of the lug stud it self.
Drifting
Joined: Nov 2019
Posts: 1,368
Likes: 99
Interesting thread. I recently rebuilt an engine in my garage and there are several areas where the manual calls for loctite on the threads. I wonder if the specified torque setting has that fact "cooked" into the torque value given? Wonder if there is a formula for reducing torque setting when using anti-seize also? Anti-seize is an absolute must around here (east coast of Florida/ask me how I know that lol).
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Verdad Gallardo
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
This is an old thread.... BUT the last post deserves an answer--just because.......
Anti-seize compound [I always thought it was " i before e, except after c " ???] should be considered a lubricant in this instance. Most torque specs in GM manuals are specified as "dry" specs, unless otherwise noted. As a general 'rule of thumb', you should reduce specified torque by about 30%, if a "dry spec" fastener is lubricated. For items like exhaust manifold bolts, you might be able to find specific recommendations for proper torque when anti-seize is used. Google can be your friend....
Anti-seize compound [I always thought it was " i before e, except after c " ???] should be considered a lubricant in this instance. Most torque specs in GM manuals are specified as "dry" specs, unless otherwise noted. As a general 'rule of thumb', you should reduce specified torque by about 30%, if a "dry spec" fastener is lubricated. For items like exhaust manifold bolts, you might be able to find specific recommendations for proper torque when anti-seize is used. Google can be your friend....
