za766 --In my book, the best way to repair a stripped spark plug hole is to install a Time-Sert thread repair insert, but installing Time-Sert inserts takes special tooling that's pricy enough to discourage the occasional user. I'll suggest you take a look at their website just to see what Time-Sert is about. There are other solid inserts that will work almost as well as a Time-Sert; EZ-Lok is one of the easier ones to use and doesn't need any special tools . . . but you might run into minimum purchase requirements that keep it from making sense economically. Another good solid insert is made by the Emhart Heli-Coil company, and installation kits are generally available from most auto supply stores. These are NOT wound-wire screw thread inserts (what 99.44% of us think of when we hear the name Heli-Coil), but are made from solid stock. I don't remember the name Emhart Heli-Coil uses for these, Restor-A-Thred, Sav-A-Thred, something like that. Installing any type of thread repair insert will require some machining of the head, and machining means chips. The very best technical solution is to remove the head from the engine, but sometimes other factors make a technical compromise worthwhile. If you do decide to try the repair in situ, work as clean as you possibly can. You'll want the valves closed and the piston near the top of the cylinder. If you buy the Emhart Heli-Coil Sav-A-Thred kit, follow the directions about how to drill and tap the stripped hole; if you use standard tooling for the EZ-Lok inserts, use good standard drilling and tapping technique. If you have to drill, it would be a good idea to "dub" the drill to minimize drill-grabbing. Grease-packing or grease coating of the drill and tap is about as good a way to catch and hold chips as any, just be sure to remove the tool and wipe off the chips frequently. Once you've finished machining, vacuum the combustion chamber as best you can with a small-diameter hose taped over the end of the regular hole of your shop vacuum. Or you could poke a blow-off nozzle down into the combustion chamber and try blowing the chips out between the inside of the newly-retapped spark plug hole and the outside of the nozzle. Or both. The scrub the retapped hole with carb cleaner or laquer thinner before installing the thread repair insert. The EZ-Lok insert is coated with an encapsulated adhesive, I recall that the Sav-A-Thred uses a liquid adhesive. In either case, you should be good to go once the adhesive cures. John
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