I'm having an engine rebuilt for me and my builder says one of the spark plug holes is bad and he wants to put a Time-sert in it. While he's at it should I just have him do all of them? I seem to remember seeing somewhere that Thumper does them on their upper end heads as a precaution.

 

I have no idea if it's necessary but, as you say Thumper does them, it would seem to be a good idea.

Hope this helps...

 

I would weigh the cost out. If he can do all of them at the same time for a reasonable price I say go for. It is added protection.