Sav-A-Thread helicoil kit for spark plugs
 

I had a plug hole (rear trailing) that was stripped beyond being able to use a chase tap to fix it. Because of the plug locations on the 8, standard helicoils are also problematic, as you need to drill for them, and without being able to get straight at at least 3 of the plug holes (without removing the engine,) drilling isn't too practical.

That's why I'm plugging (no pun intended,) the sav-a-thread kit. It doesn't require drilling. The actual kit I used was the Autozone "OEM" brand ($30,) but I'd assume the helicoil kit works similarly. The way it gets around using a drill is by having a boring tap.
http://www.globalspec.com/NpaPics/26...ExhibitPic.JPG
It's got some pilot threads (14mm,) a section that reams out the hole to the new thread size, and then the actual larger tap threads.
It worked great for me. The threads were severely cross threaded, but the tap went in nice and straight, and did not take a lot of force. I heavily greased the tap to catch the filings, and it worked quite well. Because it was a trailing plug hole (which is like a blind hole with a smaller hole in the end of it,) filings falling into the engine was less of a concern. Also because of this, the tap bottomed out after only cutting about 3 larger threads. My solution was to cut the 14mm threads off the tap with an angle grinder. This worked pretty well, and I was able to find the threads again (when I worked through the wheel well, I couldn't find the threads when working from underneath,) and continue tapping (2 or 3 threads at a time, remove the tap, clean the filings off, re-grease and repeat.) I got enough threads cut to use the medium sized insert (which is plenty long enough,) and it threaded in pretty easily, covered in hi-temp RTV. They provide a swaging tool to set the knurled threads on the insert into the head, but getting any force on it (just supposed to hit it with a hammer a few times,) was tough with so little working room. I'm not too worried, as the RTV should keep it in place and keep it sealed.

I can do a full (though lacking pictures) DIY if anyone is that interested. I wouldn't recommend this to the faint of heart though.

ewww the thought of filings getting in the motor scares me still....

I had one drilled out on a previous rotary (a 12A)

My mechanic/genius put an air line into the other plug hole and maintained a blast of air as he drilled. good results!

S

Loading the tap up with grease actually worked really well. I saw no filings left in the hole at all (I used white lithium if that matters. Pretty sticky stuff.) I also heard of (believe it or not) using shaving cream to fill the chamber. On the rotary you then could use a blast of air in the other plug hole to blow all the crap out (it was mentioned in regards to a piston engine, and said to just turn it over to pop the shaving cream out.)
No idea if that'd really work though. Seems like it might settle too quickly or not be stiff enough to hold the filings. Maybe some cool whip :P

:sleep:

:)