Has anyone successfully used the "Spark Plug Thread Repair Kit" from ipd?

I'm amused by their description that "you can now make a quick professional repair in minutes without removing the cylinder head."

Brief synopsis: #4 spark plug thread was very damaged on the 88's cylinder head. Approximate inside peak-to-peak distance of the threads is 1/2".

I tried to run the reamer/tap from ipd into the hole, using a ratchet socket driver. After an hour or so, I gave up and decided to buy a drill to at least remove the existing threads.

I drilled out the threads at 9/16", so the hole is now smooth inside, with enough meat for the new threads. Another half hour with the reamer/tap, and I'm still no further along than before.

At this point I actually *measured* the insert from ipd. Strangely, it has metric thread inside (M14x1.25) and imperial thread outside (5/8"-18). It's now obvious that the 9/16" tap drill wasn't big enough -- the proper tap drill in aluminum for 5/8"-18 is 37/64".

So, what do I do now? Am I stuck bringing the head to a machine shop? Or am I better off locating the correct drill and a REAL tap at an industrial supply shop? Any tips appreciated!

Michel

1979 242DL
1988 244DL