Helicoil engineblock lc8 990 possible?

Hello!
An ktm stealer changed base gaskets, bolts and did a valvecheck.
The mechanic said that one bolt took some thread with it when he tried to change it.
He only cleaned the thread with a tap and mounted the new bolt for the cylinder and head.

Ever since i had a problem with oil in the coolant.
Changed the waterpump already, did not help me!

So has anyone helicoil the engine block?

Im doing a plate in steel that will guide the drill.
And helicoil it.

But has this been done? With good result?

I would use a time sert kit.