I called Bart Lalonde at Aero Sport Power late Wednesday afternoon to discuss my spark plug thread issue. Based on my verbal description, he is quite satisfied that all I need to do is replace the helicoil thread insert. He talked me through retapping the threads that the insert screw into and putting the new insert in - I'm satisfied that I can safely attempt this task. He also mentioned the difference between thread inserts for cars and Lycomings, and said to be sure I had the correct type. The ones for Lycomings have a serated outer edge on the outermost thread to help keep it in place. The ones for cars don't have those serrations. The ones that I was given by Ron M didn't have the serrations, as near as I could remember, so Bart offered to send me two thread inserts - no charge. Great support!

Saturday morning I went out to the hangar early. I confirmed that the thread inserts I had were the automotive type. I was going to retap the threads in the head, but discovered that my tap wrench was too small to fit over the large shank of the helicoil tap. I couldn't find a compatible tap wrench at Canadian Tire, NAPA Auto Parts, Princess Auto or Busy Bee Tools, so I gave up for the day. I assume that Ron M. has a compatible tap wrench, and I should be able to track him down this week. Failing that, it shouldn't take too much torque to run the tap through the threads to clean them up, so I'll find a piece of stiff hose with an ID about right, use a hose clamp to secure it over the end of the tap and put two holes in the hose so I can stick a screwdriver in to turn it. I could just use an adjustable wrench on the end of the tap, but it is hard to get it started straight if you are doing it that way, and this cylinder head is worth too much to risk screwing it up.

When I went out to get the newspaper this morning I discovered an envelope from UPS on the door step. It turns out that they delivered the thread inserts from Aero Sport Power mid-day on Friday. I'll get out to the hangar sometime this week to try replacing the thread insert.