i've never installed cams on a 3v before but i have extracted many a broken bolt in my line of work before. there are a couple ways to go at it depending on the circumstances.
1. is there any "meat" on the bolt that you can use a hammer and chisel and back it out by tapping it around. if you try this, make certain you don't get into the threads. that will make it exponentially more difficult for the next step
2. easy out. its best to drill in the center of the bolt. use a center punch and indent the bolt where desired as needed. if you cant get a good center punch because the bolt snapped awkward, you can use a dremel or pencil grinder and a burr bit and knock off a little. when drilling, high speed isn't always the way to go. there is a feed rate and bit speed for each bit. bolts are hardened, so you need to start with a small bit and work your way up gradually. the bigger hole you can get in the bolt the bigger the easy out you can use and the more pressure it will relieve on the bolt. just to go back, start the drill slowly and get a good hole/indention going. small bits don't drill well at high speeds, they will burn up. which is probably what happened. if its really tight, you will need to use the appropriate sized easy out. a smaller easy out will break depending on the torque of the bolt. drill the bolt as deep as you can. the deeper the better. when using the easy out, tap it in firmly. don't hammer-slam the dickens out of it. it will come to a pretty abrupt stop. begin to loosen it. pay close attention if the easy out is turning the bolt or if it is slipping. if it begins to slip, tap on it a little bit more with the hammer. then try again. easy outs are hardened as well and will snap if you apply to much force and the bolt doesn't give. then you will be screwed, no drilling through that metal. that is why you want to use a bigger one. also, the square easy outs are better than the rounded/swirly ones.
3. if you have a welding machine, you can tack a nut on the end of the bolt. then use that nut to back out the broken bolt.
considering the price of a cyl. head is outrageous, and removing it a good little job, preperation here is key. cliff notes: drill the bolt out as best you can in the center. don't settle for a little hole, drill it almost completely out to the edge of the bolt threads. the drill bit will have a tendency to walk if not center punched so start slowly and let the bit dig out a good bit of metal. high speed generally isn't necessary unless you want to ruin your bit. tap the easy out in firmly. slowly apply force to loosen, tap easy out in further if it begins to slip. pay close attention. if you get a good bite, and bolt doesn't start backing out, be careful of easy out breaking. you'll be screwed if it does. THE END
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