TOPIC:

Remains of the bolt should easily drill out with a sharp HSS drill bit and some cutting fluid.
The core should be relatively soft but if not use a cobalt bit.
Carefully centre punch and start with a 3mm - 1/8th inch bit.
Once you got that in go 4mm the finish with 5mm.
If you are dead centre the thread coil will be left and should either pick out or easily clear with an M6 tap.
Stock bolt is never as long as the threaded hole so if you do catch the thread towards one side a longer bolt will still tighten.

I personally have had good luck with the helicoils and not with the key locking inserts. Not enough experience with the timeserts to judge so I did a little digging to see what I could find that was fact based. Found this youtube video that had merit to it's testing.


Les Holt
PDM Custom Fabrications

Hi les holt,
That's very good empirical data. Thanks for finding & posting that!

Good Ridin'
slmjim & Z1BEBE

Ok... just my 2 worthless cents on this subject matter.....

Regardless of the manner you go, PREP is everything.
For us DYI, heli coils are easier to prep/install henceforth easier not to F-Up..... As others mentioned,, certs require more medal to be removed and will require ideal insertion depth accuracy for ideal installations, cover fits, leak prevention etc...

Now key logic for CAM cap / valve cover bolts, engine case/cover bolts etc... How much torque on the bolt are you requiring... that's right very little - SNUG fit only.

Conclusion, save your self a huge headache and go with Heli coils for most applications you'll be just fine.

OMR

Old Man Rock wrote:

Ok... just my 2 worthless cents on this subject matter.....
Regardless of the manner you go, PREP is everything.

+1

For a good centered bore i use special center punches (a broken cam cap bolt).

Static or adjustable center punches dependent of the bore diameter.




and than a counter clockwise drill bit, mostly the broken part of the threat came out easily during this process!!!




Michael