Off Topic Again - Nord Lock Washers Slipping on Exhaust Manifold Bolts

Most stainless bolts are a LOT weaker than their carbon steel brethren.
Cold working improves the SST strength, but you are getting hot enough to erase much of the gain.

I'd switch to carbon steel and crank it tighter.

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Is there something to set against, If so maybe a header trick like a "Stage 8" set up would stop the loosening.

www.stage8.com

Stage 8

The World's Best Locking Fastener
www.stage8.com www.stage8.com
 
Update and question:
I have traveled over 2000 miles since the instillation. 6 of the bolts are 'set', they do not loosen. 4 of the bolts loosen moderately, less than 10 to 20 degrees to retorque. 2 of the bolts loosen and require 45 to 60 degrees to re-torque. There is no pattern to the 2, they include both dry connections and one with nord-lock washers.
I am hesitant to tighten additionally. The mounting is a bit unusual; the connection tab on the manifold is 2 inches from the head. It is well braced with side supports, but never the less it is not supported by the head directly. I am not comfortable over torqueing the tabs.
 
Trash any and all lock washers. Use steel bolts and hardened flat washers. In my experience, the more positive surface contact you can get, the better. My .02
 
dansawyer said:
I am hesitant to tighten additionally. The mounting is a bit unusual; the connection tab on the manifold is 2 inches from the head. It is well braced with side supports, but never the less it is not supported by the head directly. I am not comfortable over torqueing the tabs.
Click to expand...

So, I had a brain cramp, your description of the manifold threw me for a loop. Not your fault, I brain cramped over the word "tab". I couldn't picture it for some reason, so I googled.....

No chit Dick Tracy.... That type. OK, we had one of that type, I think it was the C7 though. (That's pretty much just a 3126 with aftertreatment). Never had any bolts com loose. In the following Google picture though, it appears that Cat had another accessory here for certain applications or build combinations or something. No rime or rhyme or reason to where thy do or don't show up in the pictures... Wasn't listed on any of the ones we had, I've never seen those in my life, but you'll recognize what I'm talking about as soon as you click on the link...

 
Yes, those were the original mechanism. They were ok for manufacturer but nearly impossible to bend the tabs in the current application. I am trying to avoid that solution, it took me nearly forever to work them loose; they are hidden and covered behind the turbo and the thermostat housing. (I would like to be able to remove the turbo and the manifold in the future. )
I am having success with re-torqueing them. Only 2 bolts are now working loose after 12 hours. Those happen to have copper washers so I will remove those.
 
Loose all the fancy hardware and order oem parts. many exhaust bolts have an interference fit thread. Stainless is terrible for high heat/stress fasteners.
 
This like the right answer. I will look for 10x1.5 - 200mm safty wire bolts.
Thanks for pointing this solution out.
 
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