I celebrated too soon.

I noticed the morning after the repair that exhaust was leaking from where the exhaust manifold meets the up pipe. I tightened the nuts/studs a bit too much and managed to shear one of them off again. I did not replace the gasket, so hopefully a new gasket, and, obviously, a new stud will do the trick. The gasket did not look great but I had reused MLS gaskets for this type of fitting many times in other vehicles so I gave it a shot. Now I have new gaskets on the way and will have to do it all over again.

 

Well, one thing I noticed was that you replaced a steel stud with a copper one from the parts store. I was hoping for the best for you and didn't want to rain on your parade but the shear strength will be MUCH lower with a soft copper stud. These joints are often problematic in the first place and in my experience require higher clamping force to seal so you may want to go back to steel.

 

They are copper plated (or maybe just colored) steel. To help prevent seizing.

 

You're probably right that they're not solid copper however the plating process itself will increase the hydrogen embrittlement and make the studs weaker and more susceptible to cracking/shearing. I would use plain steel studs with copper nuts for the anti-seize properties it brings.

 

I replaced the exhaust manifold to up-pipe gasket, as well as the exhaust manifold to head gaskets. This went much easier this time since I knew exactly which tools I needed and exactly what I needed to do. After I fired it up and the engine warmed up, I noticed smoke coming from exhaust manifold and the manifold to up-pipe joint. I got to thinking and did a bit of googling, and concluded this must be the anti-seize burning off of all of the threads. I will have to give it some miles to know for sure. This may also be what was happening the first time I did the repair, and I just didn't think of it.

 

That’s a good guess. I’d say it’s fairly common to have some smoke after a job like that, until any residual oils from the work burn off