E30 Zone

I was replacing the non-existant thermostat on my M40 lump this afternoon, and as I was tightening one of the thermostat housing bolts, I just suddenly got that awful feeling when a bolt on your cylinder head gets stripped of its thread. The other 2 bolts are fine, it's just the top one thats stripped. What can I do??

The only real fix is a helicoil thread repair.
This comes as a kit for the M6 bolts?
Anyway you very carefully drill the hole out to a size bigger than the original 6.3 I think?
then use the special tap supplied the rethread the hole. The tool supplied
allows you to fit the helicoil thread repair into the hole taking it back
to the original M6 thread size. Job done.
I know it sounds complex but with the kit for the right thread depth
it is real easy.
You can get the kits from any decent proper tool supplier.
Not Halfords as they will send you to a tailor for threads.