[Shop-talk] installing a helicoil

[Randall]

> you probably have a 60/40 
> chance..

IMO if you can tap a hole, you can install a Helicoil.  I'm not particularly
good at working free-hand, and I've never screwed one up enough to have to
take other measures.  Ruined an insert once, but only because I didn't turn
the tap deep enough.  (Was threading a starter bolt hole that ran through
the mounting flange and into the bellhousing; didn't realize how thick the
flange was.  Bolt jammed against the insert and came out with it attached.)

> ...If you
> screw it up you not only have the cost of a Helicoil kit but 
> the cost of a new head. 

There are inserts available that will work in a hole too big for a Helicoil.
For example:
http://www.timesert.com/html/bigsert_sparkplug.html

-- Randall