I bought an insrtd installation kit from Clarks Corvairs. It has a special cutter to counterbore the top of the hole to clearance for the top of the insert.
I added a long extension to the tap wrench to get the handle up above the engine studs, I got distracted by the phone ringing and when I leaned over to answer it, I pulled on the handle too hard and broke the tap.
There may or may not have been some colorful language shouted at this moment.
Luckily, this happened when the tap was about 90% of the way through. I used a crescent wrench to turn the tap a few more turns.
