Maxwelhse

It sounds like GM would have you throw away the entire car during every service procedure (in my experience with their products that might be wise). I mean, the oil plug has threads and a torque spec, right?

Header bolts are so under-worked anyhow (15ft-lbs of torque?) that any argument for metal fatigue (caused by harmonics or thermal expansion) or thread stretch is pretty absurd. I'd have to read the article or attend the class to make an engineering argument about their point, but in this limited case there is virtually no risk of issues resulting from a "failed" bolt. Corrosion kills exhaust hardware which is why I went with ARP stainless hardware when I put my headers on.

Usually when headers get loose all the time there are 2 main reasons: poor quality headers excessively expanding and contracting (thin flanges) working the bolts loose or cheap gaskets that are doing the same thing.

Wrenchman1

LOL, And crappy hardware!
Ive had stock factoy header bolts (used) snap. on retorque.
ARP could be a different story?
Just saying, From my experience.
Key hardware, Head, intake, exhaust ect should be replaced.
Do what ya want

Maxwelhse

Fair enough. Crap = crap and it's impossible to tell until it happens. Can't lose with ARP.

WJBertrand

I know with Toyotas, you can reuse the bolts/studs but not any of the nuts in the exhaust system. Daughter had Paseo that kept blowing the exhaust gasket. Finally broke one of the studs and sent daughter for some new ones at the dealer as I set about removing the broken stud. While there, the parts man informed her not to reuse the nuts so she got new ones of those two. When I looked at the new nuts I noticed they weren't perfectly round - slightly oval. Running them over the studs, which are round, causes interference and keeps them from loosening.

Never had another blown exhaust gasket after that.

Maxwelhse

That's a type of locking nut. It would be like re-using a nyloc nut, which you shouldn't. Those ARE only good for 1 use.