I have several thread repair installation kits in the shop. The problem seems to be, I never have enough or the correct size. It's a tool dealer's bonanza, they love me!
I watched a procedure done on one of the popular TV truck shows recently, dealing with the Ford truck "broken spark plug, damaged thread" syndrome. They advised using the correct special tool(s) for this because of the different expansion-contraction rates of the dissimilar metals of the cylinder head and the popular inserts. They had some special inserts, designed expressly for the aluminum Ford head, same metal spec. They say tests indicate the inserts, properly sized and installed are as strong or stronger than the original threads.
The keys were, proper tools, proper procedures, grease on the tool to catch the chips, etc. The pilot for lining up the reamer looked well designed and fairly easy to use. They used a one-piece solid base replacement spark plug to prevent the tip from breaking off in the future. The problem seems to stem from long (100,000 mile) service intervals.
Good idea if it saves a head! :msp_wink: