Rapid 12-250 blows out the Grub screw

[rsedwards1]

have a Rapid 12/250 the 4BA thread is stripped holding the exhaust valve .it blows out the Grub screw this only happens on firing and no leak otherwise.
I have a hele coil kit , but was told that a new block is the only answer any thoughts appreciated.

[Ca_Varminter]

I would re-tap the threads one size up..
I believe it would be a 4mm thread....
A couple of members have done this Fix!!
https://rapidforum.co.uk/forum/index.php?topic=4309.0

Good Luck,
Stuart