broke bolt off in head

[scook]

I got a kit called TapOut (some acid and a gob of clay) at a machine supply place when I broke a bolt in my I/O engine. You drill out as much of the center of the bolt as you can, build a little dam around the bolt and fill it with acid. When the acid quits bubbling you change it (if you can't tip the thing upside down to dump it out, you can soak it out with a cotton swab). It took a while but it got the job done. Since you never get the hole exactly in the center of the bolt, it'll usually eat through one side and you can probably worry it out of the hole at that point. The acid eats steel but doesn't damage aluminum - as long as you can keep it away from any iron you don't want eaten, you're in good shape.