If the stud is not brass or stainless you can burn it out with a cutting tourch, WHAAT!?! you say, yep, I've done it many times, what I do is hack saw the stud flush with the flange , chuck the manifold on a drill press and drill a small hole through the center of the stud all the way through so I can see daylite, take a small burning tip and burn the stud out, carry the heat in the center of the hole you drilled, the sl*g will exit through the the other end of the hole you drilled, as you watch the stud melt away from the center of the hole you will be able to see the threads appear, untoached, the reason why this works is because the melting point of cast iron is way higher than carbon steel, all you have to do is run a tap though the threads to clean them,....I USE THIS METHOD AS A LAST RESORT..... the other way to do it is take nut that will slide over the stud and weld it top and bottom to the stud with a wire machine, try not to undercut the stud, let it cool stone cold, clamp the manifold in a vise take a small oxy-acc. welding tip size 0 or 00 and heat the boss of the bad stud while trying to move the stud with a box end wrench, if you get it to move work it in and out gradualey till it comes out, don't over heat the boss to where the stud gets hot, .....NO GUTS, NO GLORY.... if your not comfortable with these methods theres always the ole muffler shop. anips2009-07-05 10:04:59