I have been able to drill and tap 3 of the 5 so far. To get around the potential walking problem, I bolted on the manifold and in the hole I inserted steel spacers that I used as guides for the drill bit. The spacers are 3/8 OD and 1/4 ID. I had to wrap a couple of winds of electrical tape to make them fit snug. Then I used a 1/4 inch pilot point drill to start a small hole in the center of the bolt. I then used a 1/8 drill bit to drill out the center then followed that with 1/4 inch. That worked well for 3 of the broken bolts. The last 2 I have the 1/8 inch drilled out but I cannot get any 1/4 inch bits to bite. I wonder if someone used grade 5 or 8 bolts in the past.
Any suggestions on what type bit to use? I've tried split point, pilot point, red helix; DeWalt, Milwaukee and Bosch.
I am neither a fast mechanic nor a slow mechanic. I am a half-fast mechanic.