The Turbo will cause Blue Smoke if the Exhaust side leaks Oil.

when I pulled a Manifold Stud out of My Head it had enough room for 4 completet threads. I guess that is about 9mm.
I never thought checked to how deep the Hole was in the Head.

The Nuts on Mine were also Copper. I am guessing the idea is that they are not going to get tightened Much.

I did find that My Exhaust Manifold had some warpaged and had the fixed before I re-installed it.

Apparently longer Studs are not actually needed. You seldom read on Mercedes Forums where the 617 Engines have a Exhaust Manifold leaks.

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84 300D, 82 Volvo 244Gl Diesel