Had the same s**t happen to me on the very first EA head that i done.

Cracked a few sockets, welded an old one on and ended up breaking the weld, tightest f**k bolt i've ever done.

I got the s**t in the end and dropped the 2 valves around the bolt, i got the angle grinder out and very carfully ground the head bolt down to the surface, i lifted the head off over the top and then the hard s**t began.

I had the stilsens on it with a 3 ft pipe for leveridge and had the oxy on the bolt, i had 2 goes at it and i was ready to call him and tell him to come and get the heap of s**t, i decided to have 1 more crack, heated the f**k out of it and it finally broke free.

I've done s**t of them since then but never copped another bolt like that.

Did you oil the bolts before fitting them last time?

i've had them that tight and one of the things i've tried with about a 60/40 success ratio is hit the head of the bolt with an arc welder. in theory it heats up at lightning speed breaking whatever the seal is holding it.

but then i've also had a laser that the bolt head had snapped off cos the stud was seized in the head. we ended up getting a secondhand engine for that one

yeah mate all ways, i think i mite drown them in oil this time

Before installation this time, tap the threads in the block.
If you don't have a tap, grab an old head bolt and cut a cpl of slots up the side of the thread with an angle grinder.
Spray a bit of CRC on them and run them up and down, after that get the blow gun on the compressor and blow them out, put a rag around the top so the s**t doesn't spray the engine bay.

Be careful how much oil you put on them cos you may finish up with some spilling onto the block surface.

what i usually do with head studs when i do them(regulary) is dip the first cm of thread in clean oil and install the bolt and put a lil bit of oil on the head/washer then spin them down till they just touch, install all bolts then quickly torque them all down.

not too much oil on head of bolts as you dont want to contaminate the gasket or block or head surfaces