Broken bolt removal:
This is for 5/16" bolts.
1.) A word about the links, if they don’t work, do a search on the part number (P/N). MSC updates their catalog regularly, and the pages may change, but the part numbers don’t.
The prices here may be old and out of date, but the part numbers should still be good. I recommend that you do a search using the part numbers.
http://www1.mscdirect.com/CGI/NNPDFF?PMPAGE=1096 Use drill bushing 5/16” OD, 5/32” ID, ¾” long, P/N 07010457, price $12.49 This centers the drill bit in the housing bolt hole so you don’t get off center and damage the manifold.
http://www1.mscdirect.com/CGI/NNPDFF?PMPAGE=27 drill bits - use 5/32” Cobalt/TiN coated bit. P/N 83240556, price $4.17
http://www1.mscdirect.com/CGI/NNPDFF?PMPAGE=1928 Screw/bolt extractors. Use EZY-OUT Screw Extractor P/N 63760037 Price $4.16
One step specialty item: See Drill-Out® Broken Bolt Extractors drill bushing, reverse twist drill & extractor all in one unit. Best to use when the bolt breaks off with the remaining part below the start of the threads. .P/N 05027164. Price $24.40 each.
You MUST have a reversing drill motor (either air or electric) to use this bit. http://www1.mscdirect.com/CGI/NNPDFF?PMPAGE=19268
2.) Test fit the drill bushing in the hole – this assumes that the bolt broke off below the surface. If the bushing is too loose, use some scotch tape wrapped around it to make a snug fit. The drill bushing helps center the drill bit up on the broken bolt so that it does not get off into the manifold. If the bushing does not fit at least 3/8” into the manifold, you may want to consider removing the manifold and attacking the remnant of the bolt shank with a propane torch and Visegrips. If not, then find a drill bit big enough to drill off some of the remnant of the bolt shank until you can get the drill bushing in the required 3/8” or deeper into the manifold. You will end up using the upper manifold to center the large drill bit on the broken bolt shank. This is not the best plan, since the aluminum manifold is soft and it would be easy to get the bit off center and damage the manifold. Alternately, you can use the upper manifold to center the drill bushing and use the 5/32" bit to drill the hole for the bolt extractor.
3.) Once you have the drill bushing in place, chuck up the drill bit and drill the broken bolt. Use lots of WD40 to cool the drill bit. If you break the drill bit off in the bolt, it is time for a trip the automotive machine shop. Drill bits and easy outs are extremely hard and cannot be removed by ordinary means. It takes a solid carbide bit and extreme care to remove a broken drill bit or broken easy out.
4.) When you have drilled about ½” into the broken bolt, then remove the drill bushing and use a hammer to tap the easy out into place. Then chuck up the easy out in a T handle tap wrench. Turn the tap wrench slowly counter clockwise and you will feel it dig into the broken bolt. If it starts to slip, tap on the tap wrench with the hammer to reseat the easy out into the bolt.
5.) Keep turning and one of three things will happen:
a.) The bolt will come out and your efforts will be rewarded.
b.) Or the easy out will continue to slip and more efforts will not make it grip. This means you get attack the bolt remnant head on. You get to drill the bolt out to a thin shell & either re-tap the hole or install a helicoil threaded insert.
c.) Or worst of all, the easy out will break off it the bolt shank. Then it is time to go to the automotive machine shop and pain in the wallet.