I wish I had caught this thread a bit earlier.

Reading through it, I expected this to be the case.

Throw the EZ Outs in the trash. If a left handed drill won't get it out, and EZ Out won't do it either.
Those things are really hard so they will drive into a bolt. That makes them rather fragile and they'll snap before a nicely seized bolt will release.

A left handed drill bit will be constantly digging into the broken stud and often catches well enough to start turning the bolt out.

No doubt I'll catch grief for this post but I make good money on the side by removing broken EZ Outs and snapped taps.

Now you're down to drilling the bolt but you have to be on center or things can get ugly.

The valve cover bolt bosses go over the water passages. If you punch through the bottom you'll have a wet valve cover bolt.

Any time the broken bolt is too short to grab and near the surface of the work piece I'll weld a nut to it and spin it out. That works in two ways.
1) It gives you something to grab.
2) Constrained expansion.

When you heat metal it expands in all directions. When it cools it shrinks in all directions.
Heating a bolt stuck in a hole (through a torch or welding) will expand the bolt. Since it is tight in the work piece (cylinder head) the bolt can't expand that way. Instead, it expands lengthwise. When it cools it will still shrink in all directions. That is what breaks the bond and makes it easier to remove.

As for the broken EZ Out you can use a sharp punch and hammer to get it out. It'll break easily but you'll have to keep dressing the point on the punch. Use a stick magnet or magnetized pointy tool to retrieve the broken pieces. Don't let them fall into the engine.


Here's a broken head bolt I did not too long ago.