Went and pulled the heads off today and the threads in my block decided they've had enough and will no longer accept full torque.

Any good remedies short of a new bare block?

I am leaning toward using heli-coils and studs epoxied in permanently.

I don't know if you can, but can you drill and tap to the next bigger size?

Either way, they will have to be drilled and retapped. Assuming you will go back with the same stud size when using the helicoil. If you can I would go the helicoil route but forget the epoxy.

Either helicoil or tapping to the next size up will be alot cheaper than a new block. Anything is repairable. Ive seen v6 Mercury blocks get broke in half due to broken cranks and believe it or not, get welded back together and re-sleeved and be like new in no time.

http://www.timesert.com/ Give something like this a try we use something similar at work alot and they seem to work very well.

Jergens brand are the ones we use

Briggs is running M9 bolts, and studs are a bitch to find in a 80mm+ length for them.

M10 studs are readily available, so long as there is enough material to work with.

I believe what did the threads in was the repetitive swapping of different head configurations for testing.