How to drill out a broken head bolt

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Here's some pics of a successful broken head bolt removal. If you buy a used engine with high miles that has never been taken apart you might break a head bolt when removing the head. To fix this you need to file the top of the broken bolt flat, Then you can take a very sharp center punch and strike it dead center. I cover the top of the engine so that the shavings don't go into the cylinders. Next step is to start with a small drill bit and two helpers. Drill a starter hole all the way through. Now start putting PB Blaster in the hole and bang the bolt with a hammer. Take your time. If you screw up the block is going to need a Heli-Coil. The helpers are there to adjust the angle of the drill so that you get a straight hole. Next drill with a slightly larger bit than the last one until you get almost all the way out to the threads. Using a screw extractor like the one shown, insert it into the bolt. While trying to unscrew it have someone tap the top of the extractor to help it get a good bite. Take your time and use lots of PB Blaster and banging with a hammer.

Nice looking block except for a broken head bolt!!!



The broken bolt.



Protect the cylinders.



File the bolt flat. Nice use of cardboard and bungee cords!



Let the drilling begin.



Now step up one size drill bit,use lots of PB Blaster



The only screw extractor I would even consider using for this job.



Ah, Success!!! A perfect extraction, next patient. You can see where the PB Blaster has soaked up the through the bottom threads. Total time 1.5 hours.