Hopefully you got it out by now good luck if your still battling this screw.
I've had great results using the technique explained by WhizzbangK.C..
Here is a thread on another forum fella had to resort to using a Dremel and carbide cutter..
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Hey am new to the group recently bought a 1957 t110 engine needs refreshed. This is my first triumph and first full engine rebuild. Am ready to split the cases and it’s been done before at some point in it’s life and the last person to do it stripped one of the case Flathead throat bolts out...