wow, that edm is too cool. with all that i spent on taps,extractor sets, drill bits, mil bits, and dremel bits, i was a 1/4 way to the cost of one of those EDMs. still that would require the removal of the head, so i've just stayed at it, trying not to bugger it worse.
this weekend i broke through the other side and was pretty excited.
it's taken me a month of serious chipping at the bolt to clear it out.
then today i was able to pick up another tap - 10mm, same as the original hole. it looks like half the threads survived.
anybody know if half threads are sufficient to hold? its supposed to be torqued to 32 ft/lbs. its the last bolt to tighten in sequence of torquing the manifold.
honestly, i think the upper surface of the hole is thread all the way. the camera angle is the same angle as my drill access. so what threads you dont see are probably there.