freetors said:In reply to Tyler H :
Just one thing I'd like to point out that is a commonly repeated fallacy, socket extensions do not effect torque values! (Assuming that you can hold your extensions straight. For a static case like torquing a fastener torque in must equal torque out because Mr Newton. Yes, the shaft twists but the previous statement still holds true. You can try it for yourself, go get the longest extension you can and experiment.
Agree, but not when u-joints are involved.
"Tighten it 'til it squeaks, then add half a turn" used to be a wheel nut joke, but that's how Germans tighten their head bolts now.
The0retical said:I'm a certified A&P, so torque specs are basically gospel in my world.
If I'm nervous about torque due to a custom application it gets safety wire or loctite.
Seriously. Tell them about the "Jesus" nut.
In reply to Tyler H :
For sure. I just wanted that out there because I hate seeing misinformation being parroted around. There are people out there that truly believe that just adding a socket extension will make your torque wrench inaccurate.
I broke a lot of bolts early on. I am now highly calibrated.
Pet peeve: Oil drains and filters. Some folks really need torque specs.
Another thing to consider is not just the torque but the procedure.
Let's take LS rocker arms for example, because my brain is still full of berk when I think about it.
The rockers are tightened down hard against a carrier, and there is a torque spec. It has been a while but I think it is something low like 18ft-lb because they are 8mm bolts. Fine. Good. Fine and good. But the procedure, if you RTFM, is to torque all the rockers, then rotate the crankshaft 360 degrees and retorque.
The part that blows my mind is that, yes, the rockers were tightened down tight against the rocker carrier. And after rotating the engine, some will be loose again. The torque is more than enough to compress the valves and the lifters, why are some of the rockers loose???
I don't know. But it is situations like THAT that make me just shut up and follow procedure when GM says to loosen the center cam caps and retorque after you tighten all the cam caps on a High Feature V6. And when I do heads on a Subaru, I do the full hokey pokey of tightening and loosening.
If there wasn't a good reason for them to tell me to do all that extra work, they wouldn't have told me to do it.
Back in the cast iron age, I knew a guy who would torque the head bolts, then give each bolt a rap with a hammer, then torque again. Often got a bit more movement.
We also retorqued at 1000 miles, but that is before the age of six hours work to get to the head bolts.
Streetwiseguy said:We also retorqued at 1000 miles, but that is before the age of six hours work to get to the head bolts.
And Felpro head gaskets
Does anyone know of another feeling as bad as when you are torquing the last head stud an hour before your race and when the torque wrench is a few ft-lbs short of target, it all of a sudden gets easier to turn?
Do you stop and race as is? Do you park it because you don't have a new head stud and even if you did there isn't time before the race to pull the head again? Arrgggh!
And although I use good hardware like ARP, there is a ton of cheap Chinese or Indian (or God knows where from) that are mismarked and/or cheaply made and not up to the job, so it can bite you in the butt even if you think you are taking care.
In reply to wspohn :
I haven't had the exact same scenario, but I know that sickening feeling. The torque wrench starts turning so easily and your stomach just drops. It's like being at the top of a roller coaster hill, you know it's going to be a rough ride down.
BTDT. In my case, one of the blind head bolt holes was cracked, as if someone didn't clear the water out before ramming a bolt in there at one point.
The squee-squee-squee-BINK sound of snapping a bolt is one of the most sicken sounds in the automotive world.
snailmont5oh said:buzzboy said:
I helped a guy working on an engine and watched him use the inch-pound wrench to install a valve cover. I thought that might be a bit much.
That guy broke the flange off a $200+ set of aluminum valve covers once.
Valve cover gaskets can be very sensitive to leaking if torqued too much as well. "Valve cover leaks - tighten MORE!" and then it leaks more... imagine that.
I've spent a lot of money on a half-dozen torque wrenches over the years. Seems silly not to use them. Plus, the torque spec for a lot of suspension parts is considerably less than "gutentite". Plus, Germans have near exact torque values for EVERYTHING. Not a range, but usually some precise odd number, like 41 NM or something.
In reply to Knurled. :
That sounds about as convoluted as the torquing procedure for VW front wheel hub bearings. Torque some crazy number (150 ft lbs, IIRC), loosen a 1/4 turn, lower the car, roll forward half a wheel rotation, then tighten 180 deg. (going by memory here - RTFM if you actually need to do this job) Get it wrong and you'll be replacing the damn bearing again in less than a year...
For me it's not that i don't trust the torque value, i just don't trust that a torque value alone means it's ok. A torque wrench doesn't tell you that the threads are so dirty/rusty that you hit X lbft without actually clamping the part properly. Or that the bolt is slightly too long or in the wrong hole and it just bottomed out rather than clamping down even though it 'looks good'. I trust the feedback i get through my fingers more than i trust the torque wrench.
Not that there's anything wrong with following torque values. But the concept that X torque = X clamping load relies on a few assumptions and if you're not doing due diligence then just clicking the wrench is no guarantee that it's right.
I've found most people over tighten E36 M3 on regular basis. YMMV.
Also if you're going to use a crappy torque wrench, or one that isn't take care of and maintained, might as well not bother at all.
FWIW, I have a Summit/Harbor Freight torque wrench that is 20% high at the ends of its range and 10% high in the middle. In the forwards direction. In reverse (it's double sided, you can stick a spline adaptor right into it) it is up to 40% high.
Everything that's been worth saying in here has already been said so I'll go on a tangential path here. I work in a CNC machine shop and I build tooling and fixtures often. Many times these fixtures will have blocks and components bolted together. It is truly incredible how well and nice feeling brand new threads are in two blocks of metal with very flat, machined surfaces. They build torque amazingly fast. They go from finger tight to TIGHT with a very short turn of the wrench. Every other threaded fastener joint out in the field and on cars and stuff just feels like like mush.
I am just tightening the lug nuts on the SE for now whilst I get the new caliper bracket delivered installed and ready to drive. I figure if I haven't driven it yet why bother. I do have to find out what the actual specs are however. 
Watched a tire shop kid run my lugs on with an impact gun, hard.
Then he walked around with the torque wrench and when each nut caused the wrench to go "click" he proclaimed the job to be done.
He didn't seem to understand why I took issue with the procedure he was using.
O.P. Did you work for Tireland in Richmond B.C. at some point? We may know each other. 
BTW, has anyone used Torque sticks? They seem to be accurate enough for tire shops, although I always use a torque wrench myself.
In reply to wspohn :
I really only use them for very specific applications. In my case tightening down the top nut of Koni Yellows with a set of camber plates.
I find the torque wrench to be a more flexible tool and the sticks are one more thing to have sent to calibration.
I was hoping this discussion would be about the fact that torque isn't really the value we actually care about. Regardless, I learned a decent amount from this. Thanks, Maschinenbau.
I come from the bridge and structural fabrication world, so my perspective is going to be a bit different - you're not going to snap a 1" diameter high strength bolt while tightening it. Anyway, what we really care about is tension but we don't have a good way to measure it. Torque is easy to measure. In bridge work, "Turn of the nut" method is most common. Connections are bolted *snug, then the nut is turned some fraction of a turn dependent on diameter, grade, and length.
In some states (Kansas for sure), a special washer called a Direct Tension Indicator is used as an attempt to measure bolt tension. See this link if you care to learn more.
Rotational capacity tests are performed on each possible combination of lot numbers of bolt, nut, and washer. The tests are performed both in the shop and in the field, and I think the field test is performed every day. What I saw through these tests was thread condition is pretty much the only thing that ever caused high strength (ASTM A325 and A490) bolts to fail a ro-cap test. This was always caused by leaving a container open.
*I stole this definition of snug tight from the great state of Michigan. Other states use a similar or identical definition. It is incredibly vague, but this really is how our bridges are built. Snug tight condition is defined as the full effort of a typical person as applied using an ordinary spud wrench (Figure 10). A bolt in snug tight condition will carry no less than 10% of its pretension load. Snug tight conditions can also be achieved with a few impacts of an impact wrench.
Anyway, lots of words to say, I don't worry about torque values very much on things I have a good feel for. Small fasteners worry me, so I blindly follow the suggested torque values.
Appleseed said:The0retical said:I'm a certified A&P, so torque specs are basically gospel in my world.
If I'm nervous about torque due to a custom application it gets safety wire or loctite.
Seriously. Tell them about the "Jesus" nut.
It has its own Wikipedia entry because it's that good.
You know what ETOPS stands for right? - Engines Turning Or People Swimming
(I literally have to look up what the actual acronym definition is... Extended-range Twin-engine Operational Performance Standards)
We use Super nuts or Hydraulic nuts in critical torque applications like holding heavy presses together
There are no great wines only great bottles. Think about it. 
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