Again, strip the head down and weld in some metal. Might want to look for cracks elsewhere on the head, they do tend to crack in other places. Might save the head from a dropped valve seat in the future.
Again, strip the head down and weld in some metal. Might want to look for cracks elsewhere on the head, they do tend to crack in other places. Might save the head from a dropped valve seat in the future.
The Time-Sert inserts work well, the lip at the top makes them different than anything on the market and I like to think aid sealing. However...
I now have a blown head gasket. Inexpensive to buy, but what a PITA.
OK, diagnosis time: 
A). Leak around a spark plug helicoil verified by dripping water around the helicoil while the cylinder was held to 70 psi.
Helicoil replaced with better grade coil.
B). Run up to temp and recheck compression. Leaks badly, I hear hissing at the tailpipe.
With the valves closed, blow compressed air in to blow any wayward chips.
C). Run it up to temp and recheck compression. Leaks badly, hissing through the intake.
Blow air through again trying to remove chips.
D). Run it up to temp and recheck compression.
Bottled water verifies air leak at the head & jug connection.
Why is it MOVING AROUND?
I dunno about your moving leak, but the proper old school way to fix the spark plug hole with an insert of some type is to bring the piston to BDC on the compression stroke, fill the cylinder with shaving cream (via a tube on the nozzle), cut whatever you need to cut, letting the chips fly, as it were, cranking the motor blowing the shaving cream and chips out the repaired plug hole. I thought you knew that.
Packing the tap flutes with grease helps a lot too.
I filled the cylinder at bottom with shaving cream, did the deed and rotated the crank after tapping.
Going to run it again .....
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