okay, update time! let's dive right in. when last i posted, i had an issue with some broken head studs. let's start there. these things were completely welded in place; no way to extract other than to drill.
a couple of notes:
1. if you ever have to do this, BUY A GOOD AC DRILL!!! i picked up an awesome Rigid from Home Depot for around $60. it will do a much better, faster job than ANY battery powered drill
2. get good bits! i recommend Irwin cobalt bits.
3. step up SLOWLY in size, or your pilot hole will 'walk' and come uncentered as your bits increase in size. step up in 1/32" increments to be safe. if you're GOOD, you can try 1/16" increments.
4. use a pilot hole guide to center your pilots. i will post the link to the one i bought when i find it. it basically threads onto the protruding stud & lets you dead-center a 1/8" pilot hole.
5. if you have to use a tap, buy some tap sockets. they will let you use an extension from a ratchet instead of a t-handle; this will give you more room.
6. when you get up to the larger sizes just prior to helicoil insert, bolt on the manifold if you can. it will help keep the larger drill sizes centered.
7. use lubricant when you drill & when you tap.
drill pilots:
step up:
step up more:
tap:
helicoil:
result:
this obviously took awhile. FYI, helicoils are awesome. they come in 1/2" deep inserts, but you can stack two, which is what i did in this case.