<VV> plug thread inserts

[Doug Mackintosh]

On Sept 14 I posted a photo link showing a bad spark plug hole repair on the mongrel Corvair I am working on, asking for identification and advice for getting it out and repairing it properly. I have it fixed now, so I wanted to post to let everyone know the outcome. 
 
Thank you all for your responses and comments. Based on that, and some subsequent internet research, I determined that what I had was a Helicoil brand Sav-A-Thread repair insert which had not been properly installed. The insert should have been screwed down flush, then the end expanded with the tool to lock it in. Instead, the "mechanic" had left it about 1/8" proud of the surface.
 
Kevin Nash suggested coating a plug with Loctite stud and bearing mount, and installing it in the insert to screw it out. I first tried some Permatex Hi-strength threadlocker Red, but the insert stayed in. Then I tried Permatex High Temperature Sleeve Retainer and that did the trick, removing the insert with the plug. It left the aluminum threads looking OK. 
 
One person suggested that the various insert repairs all share the same thread in the head, but I found that the K-D insert (which I think is the same as Clarks C3212) has a smaller diameter and different thread pitch. 
 
Based on that, I decided to get the Sav-A-Thread kit and insert and install it properly. I retapped the hole using the tap supplied in the kit. I then first tried installing the insert according to directions, which says to use High temperature RTV. However, when I installed it (using an oiled plug as a tool) and let it set up overnight, the insert came out with the plug again. So I cleaned everything up and reinstalled using the Permatex High Temperature Sleeve Retainer. I let it set up 24 hours, then removed the plug today - and the insert stayed put!
 
One last comment. I discovered this problem after I had done extensive work and had just completed engine assembly (ready to install shrouds). Don't ask how I failed to see it before! Anyway, I was able to do the repair without removing the head. To avoid dropping chips in the cylinder, I stuck my shop vac hose (connected to blow rather than vacuum) in the exhaust manifold, then turned the crank until the exhaust valve was open, so it would blow out through the spark plug hole. Note that only one cylinder on a bank will blow at a given crank position. I saw the chips blow out while I tapped (wear goggles!). 
 
Thanks again!

-- Doug Mackintosh
Corsa member since 1996
Corsa/NC member since 1996, Virtual Vairs member
Corvair owner 1969-1971 and 1996-on