| Message | 
to the gasket surface and also tapped square. If you don't do this, the bolt will be a beotch to install. I end up rejecting cores with poor Helicoil installs all the time.  Once it's crooked, the only way to fix it is with a Keensert, and it's just not worth it when there are so many cores that are not mangled.  Here's a nice example of a crappy Helicoil install:  
 
  | 
  |