Well... now you have to be honest about your own level of patience and ability. The first issue is to remove the remainder of the broken stud. This must be accomplished in order to even revert back to the original exhaust. This is where the ability part kicks in. I have had good results with left-hand drill bits. Start small, I usually start with 1/8" and work my way up. Often, when the drill bit "breaks through" the bottom of the offending "inclined plane wrapped helically around an axis" (bolt) there is a little extra "grab", when combined with the heat from drilling, will often twist the broken right out. This is a very satisfying feeling. There's also the possibility that:
A) The drill bit will drill clear through, leaving the broken piece intact. In this case I step up to the next larger bit and drill again. Repeat until the bolt finally twists itself out (remember you're drilling in reverse with a left-hand bit), or you've drilled out as much of the bolt as possible without drilling into the aluminum threads in the head. The hardest part is centering the bit when drilling the first hole AND keeping the bit straight. If it's off-center or crooked from the start then you will be limited to a smaller maximum drill size before damaging the aluminum. If you are maxxed out on the drill size, and the bolt is still stuck, then thats when the fun begins. I've been able to use diamond stones on a dremel to further grind away as much of the often off-center (or crooked) remaining threads as possible, and then resort to sharp dental picks to start picking at whats left of the bolt threads. You can also drill it oversize and do a helicoil repair, but I like to reserve this as a last resort. The success of a helicoil repair can also depend upon both the centeredness(?) (is that a word?) and or straightness of the first drilled hole.
orrrrr.....
B) The drill bit (and your heart) breaks. These (as well as broken easy(?)-outs) can be ground out with diamond stones on a Dremel, but this is more maddening than picking out thread remains.
Sooo... you have to ask yourself now, before proceeding any further:
Do you have the intestinal fortitude to see this through, or are you going to resign yourself to pulling the motor, then pulling the head, and taking the head to a machine shop for professional help? I have never had a broken bolt beat me, even if it finally ended up with a helicoil repair, but I have nearly given up more than once...
and I happen to be a very patient individual.
