Sparkplug Thread Insert

[useng1]

I went to change the plug in a 1976 HS50. The CJ8Y that I took out had a much larger thread than the new CJ8 that I had . I put my glasses on and could see there was an internally and externally threaded "sleeve" on the old plug.[It is not a HeliCoil] The head had a larger threaded hole than the other HS50s I have. The hole was straight and well machined. The HS50 is original to a Heald VT5 I have that is in excellent condition. I don't believe the plug hole could have been drilled and tapped without removing the head. It seems to me that a new head would have been easier and not cost that much if a prior owner had stripped the plug hole. Could Tecumseh have salvaged heads with bad holes in this manner? Anybody have any thoughts?
PS- The sleeve seats against the plug gasket. There is very little of the gasket beyond the sleeve to seat on the head surface.

 

[gpxsrxracer]

I went to change the plug in a 1976 HS50. The CJ8Y that I took out had a much larger thread than the new CJ8 that I had . I put my glasses on and could see there was an internally and externally threaded "sleeve" on the old plug.[It is not a HeliCoil] The head had a larger threaded hole than the other HS50s I have. The hole was straight and well machined. The HS50 is original to a Heald VT5 I have that is in excellent condition. I don't believe the plug hole could have been drilled and tapped without removing the head. It seems to me that a new head would have been easier and not cost that much if a prior owner had stripped the plug hole. Could Tecumseh have salvaged heads with bad holes in this manner? Anybody have any thoughts?
PS- The sleeve seats against the plug gasket. There is very little of the gasket beyond the sleeve to seat on the head surface.

You can buy kits at your local autoparts store to repair spark plug threads, they are inserts just as you described, there are several different brands out there, even Helicoil has several different kits as well. Do a search on Google or hit your local autoparts store and you will find a kit there if they are a half assed decent place. They are cheaper than a new head most of the time(depending on the kit you use) and yes you can repair them without taking the head off.