Y'all's Thoughts on Torquing Bolts Correctly, Please

[homesick]

A friend and I have had this argument for years...

Let's say we're torquing the heads on a SBC, and the specified final torque is 65 Ft/Lbs.

Here's the disagreement- he favors once around the pattern at 65. I go around, at the final value, 3 times- basically until the torque wrench clicks without turning the bolt any further. He thinks my way is over-torquing.

I'm real interested in y'all's takes on this. [Of course, if he wins, I'll never tell him about this survey.]

joe

 

[strutaeng]

Umm. "Technically", if the bolt achieved 65 lb-ft, then it shouldn't rotate anymore and you are both correct. Whether he does a single pass, you do 3 passes, and someone else with OCD does 6 passes, it shouldn't matter.

In practice, however, everyone that has used a torque wrench has had at least one faster rotate a tiny bit more at some point, somewhere, some job when going around a second (or third?) pass...and the reason is a bit more technical than one would think.

 

[OR VietVet]

I believe in more than one pass. If is 65 ft lbs, then I do a pass at 50-55 ft lbs and then a second pass at the same to know that I am at the same point with all of them. Then I would do two passes at 65 ft lbs. I also use a digital torque wrench and if not handy I would use a click type. Beam style wrenches are not the way to go at all.

Also, I prep all threaded holes, in the block or in a nut, with a chase and I do not lube threads.

 

[Marky Dissod]

Let's say we're torquing the heads on a SBC, and the specified final torque is 65 Ft/Lb.
Here's the disagreement: he favors once around the pattern at 65Ft/Lb.
I go around, at the final value, 3 times - basically until the torque wrench clicks without turning the bolt any further.
He thinks my way is over-torquing.

Assuming you're talking about one final pass vs three final passes,
and assuming all three passes are truly indiscernible from one another,
it SHOULD make no difference.

More important is all the other stuff prior to the final pass(es).

Long ago, I read somewhere that Ferrari has an unusually elaborate torquing procedure for engine parts,
which seems to make sense given that many tend to be able to rev over 7000RpM.

 

[homesick]

Ok, I didn't say so specifically [my error] but we're assuming that not all bolts have reached 65 after the first pass. If one pass always did it, I'd've never started making more passes.

Does this change anything for anyone?

joe

 

[homesick]

I believe in more than one pass. If is 65 ft lbs, then I do a pass at 50-55 ft lbs and then a second pass at the same to know that I am at the same point with all of them. Then I would do two passes at 65 ft lbs. I also use a digital torque wrench and if not handy I would use a click type. Beam style wrenches are not the way to go at all.

Also, I prep all threaded holes, in the block or in a nut, with a chase and I do not lube threads.

LOL, this answer is another reason I wish you lived close enough to be my mechanic.

I used clicking torque wrenches as a stand-in for all types. I did not know that beam wrenches should be avoided. Do you care to say why?

joe

 

[strutaeng]

Well, if not all bolts had reached the target torque specification, then you obviously have to keep going until you do. Multiple passes would help ensuring the part is being clamped uniformly, but the service data usually takes care of that.

I have personally done more than one pass (after reaching the final torque specs) only to ensure I haven't MISSED any bolts. A third pass is yet another confirmation.

On TTY fasteners, I mark the bolt to keep track of which one's are done.

BTW, if anyone is interested in differences between torque-to-spec, torque-to-angle and torque-to-yield, we had a good conversation on the LS1TECH website:

Are 5.3 L33 outer main cap bolts torque to yield? - LS1TECH - Camaro and Firebird Forum Discussion

Generation III Internal Engine - Are 5.3 L33 outer main cap bolts torque to yield? - I understand that the head bolts, connecting rod bolts, and harmonic bolt, are all torque to yield. I noticed the outer main cap bolts are also marked with and angle for the final pass? Nobody on the internet...

ls1tech.com

Seems like a lot of folks confuse them, or just don't understand what is what.

 

[OR VietVet]

Since torque values are specified for a reason, if I am torgueing any bolt or nut, I am going to be sure sure sure. A second or 3rd pass is warranted, in my mind.

A beam style torque wrench is not exact enough. As I said above, if I am going to torque it to spec I am gonna be 100% sure. A beam style can be right on the money or close enough. Why torque at all if gonna be close enough. It is old tech. I believe in the digital/alarm type and then a click type, that may or may not be calibrated correctly.

 

[Fless]

I believe in more than one pass. If is 65 ft lbs, then I do a pass at 50-55 ft lbs and then a second pass at the same to know that I am at the same point with all of them. Then I would do two passes at 65 ft lbs. I also use a digital torque wrench and if not handy I would use a click type. Beam style wrenches are not the way to go at all.

Also, I prep all threaded holes, in the block or in a nut, with a chase and I do not lube threads.

This is essentially how I do it, unless the torquing steps are specified by the part or procedure. For example, when I torque my wheel lug nuts (deez nutz ) I'll run them to 100 ft lbs, then 120, then 140 and go over them again at the final. Might be overkill but keeps things even and certain.

 

[Marky Dissod]

... didn't say so specifically (my error), but we're assuming that not all bolts have reached 65FtLb after the first pass.

Final pass is incomplete until every bolt has reached 65FtLb. Mark each bolts as it achieves spec.

When I used to tighten heads or intake manifolds, I'd wait 15min before the 2nd pass.

 

[homesick]

Final pass is incomplete until every bolt has reached 65FtLb. Mark each bolts as it achieves spec.

When I used to tighten heads or intake manifolds, I'd wait 15min before the 2nd pass.

I never heard of that, but I think I see the theory. It sure couldn't hurt anything.

joe

 

[Joseph Garcia]

Like @Fless and @OR VietVet, I torque to a lower spec for all bolts, then torque to final spec, and then check one final time to be sure that I got all of the bolts fully torqued. For me, it doesn't matter whether its head bolts or tire lug nuts.

 

[GMCChevy]

Since torque values are specified for a reason, if I am torgueing any bolt or nut, I am going to be sure sure sure. A second or 3rd pass is warranted, in my mind.

A beam style torque wrench is not exact enough. As I said above, if I am going to torque it to spec I am gonna be 100% sure. A beam style can be right on the money or close enough. Why torque at all if gonna be close enough. It is old tech. I believe in the digital/alarm type and then a click type, that may or may not be calibrated correctly.

Beam type torque wrenches are more accurate then click type. The only problem with them is that you need to have a clear view of it so the click type or digital with lights and sound is a lot more convenient. Digital comes down to quality and how well they were calibrated to begin with.

 

[Doubeleive]

i go by what the book says if it says make a pass at xx and a final pass at xx that's what I do.
just don't confuse inch lbs with ft lbs (like I have before) lol

 

[bigdog9191999]

Ohhhh, so I will open this can of worms before I give my answer. ( I will answer later, getting ready for work now).

Is this based just on the mentioned head bolts, or "all" bolts that are supposed to be "torqued" ?

 

[the 18th letter]

Ohhhh, so I will open this can of worms before I give my answer. ( I will answer later, getting ready for work now).

Is this based just on the mentioned head bolts, or "all" bolts that are supposed to be "torqued" ?

I’ve never owned a torque wrench. I’ve also stayed away from work where torquing is required vs recommended, like head bolts as an example.

 

[hagar]

If you are doing something like a cylinder head or intake/exhaust manifold, you will notice that the starting point loosens off after doing the remaining bolts. Torque a cylinder head from the inside out for example to 40 foot pounds to start, then go back to the center bolts with the same 40 foot pound setting, and the bolts will take a decent amount more turn before hitting 40 foot pounds again.
I look at it as trying to get the heads or manifold to lay as flat as possible by forcing the stored energy out of the ends of the head/manifold. I will start by torquing the 2 center cylinder head bolts to 20 foot pounds, then do the 2 on each side of those in sequence, then Torque the center ones again, then release the 2 bolts on either side, then retorque them again, and carry on. Basically just using a lower Torque setting to start, then walking the tension on the head/manifold out the ends. Once you do it once with low torque, the rest of the passes usually click true once you go back and double check the center bolts after torquing the outers.

 

[2006Tahoe2WD]

Umm. "Technically", if the bolt achieved 65 lb-ft, then it shouldn't rotate anymore and you are both correct. Whether he does a single pass, you do 3 passes, and someone else with OCD does 6 passes, it shouldn't matter.

In practice, however, everyone that has used a torque wrench has had at least one faster rotate a tiny bit more at some point, somewhere, some job when going around a second (or third?) pass...and the reason is a bit more technical than one would think.

Assuming the initial torque of 65 was done properly (continuously moving until click) then additional applications with that wrench set at 65 will not move (rotate) the fastener. Reason: dynamic vs. static friction. Additional passes are used to double check that no bolts were missed.

 

[hagar]

Assuming the initial torque of 65 was done properly (continuously moving until click) then additional applications with that wrench set at 65 will not move (rotate) the fastener. Reason: dynamic vs. static friction. Additional passes are used to double check that no bolts were missed.

Not true. The more things that hold something down that is trying to resist being held down, the less effort each thing needs to put in. Bolts can totally lose their foot pound setting after other bolts around it are torqued down. Unless you are bolting 2 perfectly flat things together, but that isn't the case with auto stuff.

 

[ccssid]

Over 55 years ago, my local Harley mechanic told me ( I didn't have a torque wrench) to use a 6", 8" and 12" 9/16 box end wrench at various bolts/ nuts and snug em firm. I never had an issue.