So I bought a built engine and these guys did quite a few things janky. They apparently stripped a bolt hole in the block where an oil pan bolt goes. So I have one missing bolt. I cannot drill and tap a hole there. I tried and the drill bit broke off in the block. My question is this. Do I have any chance of properly sealing the oil pan while missing a bolt? Or am I just hung out to dry from hence forth?

 

I assure you can extract that drill bit with the proper/appropriate Bolt extractor/Easy Out bit. Drill bits are made of various hardened metals. Most often the broken drill bit which resides in the hole is of lesser hardness than the Bolt Extractor/Easy Out bit used to drill out the broken drill bit. Unless you’re a machinist, you may not recognize bits of various metal hardness are available - paying a little more in cost for that hardness. This can be done. Purchase the best highest grade metal Bolt Extractor/Easy Out bit you can afford. The highest hardness Bolt Extractor/Easy Out really won’t ‘extract’ that broken drill bit - instead it will turn that broken drill bit to powdered dust. Buy an extractor bit sized to the O.D. of the hole and drill it out. You’ll be removing threads, as well. Drill ‘slowly’ until appropriate depth required to insert a helicoil of the correct size to accommodate a new bolt of the same size as the helicoil. You may need to enlarge the oil pan hole a little to accommodate a new bolt for the helicoil. This can be done. Take your time, don’t give up. You’ll be quite satisfied with your work when finished. That’s what I would do, others may provide various equally well suggestions.

 

I assume the engine is out of the car, since you have tried to replace the bolt. If so, I don't think one bolt will allow a leak to occur unless it is one of the corner 5/16 bolts. I don't know how you managed to break on of these if you were torquing it to the proper tightness.

 

#1. You might get by with one oil pan bolt broken off, unless its a corner bolt.
#2 You can't drill out a drill bit with another drill bit........unless you use a solid carbide drill bit.
#3 You won't get a hand drill to stay centered when drilling out a drill bit.

Is the engine out of the car ?
Is the oil pan removed ?
Do you have an air compressor ?
Do you have a dremel ?
Do you have an 1/8" carbide ball rotary file (slang term: bur) ?
Do you have a bright light ?
Patience ?

 

Would it be possible to drill and tap a new hole beside the original?