Exhaust stud thread pitch?

[dragon850]

I have to use bolts on my Mk Motorsport headers, took out the studs measured and checked the pitch, it looks like M8 1.25. Got M8 1.25 zync plated bolts, tried to thread one in today, it's going in but much tighter than the stud, did I have the pitch screwed up? Can someone verify?
stud.jpg

[dragon850]

Never mind, I figured it out. Because of the zinc plating the surface of the bolt is 0.03m thicker that's why they feel tighter going in . I will just use a bit of anti seize to install bolts.

[72tpik5]

A coupe of turns against a wire wheel on a bench grinder will make those threads perfect.