Is there any bolt sticking out where you can get a hold on it ?
You may be able to use a prick punch ( OK.... Center punch ) and drive it in the loosen direction very carefully....It's a time consuming job.
Try drilling it out, if you can get a good center hole.
The last resort here is to get a oxy/Acetylene cutting torch and burn it out....
Don't worry The torch will not ruin the Cast Iron of the Cylinder head.
I have removed lots of broken bolts from Heads and blocks, it just takes time and work slow so you do not ruin the head or whats left of the threads..
Iffff you can get the head off, you could melt a little candle wax on it and then try to turn it out....I have found that Candle wax works much better than most penetrating oils
on Head bolts and Exhaust bolts....Good Luck .. "BH"
07-JKU-X /Poison spider Evap.Skid/Master craft grab handles/Or-Fab spare tire-can carrier/ Gibson SS Duals/ Q-tec Floor Liners/Hidden Hitch Receiver/ AntennaX 7inch/ 48" Hi-Lift./ 8"X16"X4"bs Steel smoothie wheels/ 265X75R-16,Kelly Safari TSR tarz.
Viet Nam Veteran 69-70, Troop "D" (AIR) 3/4 Cav. ,25th Inf. Div. CUCHI RVN. UH-1H Crew Chief of the "Pinball Wizard" 68-16224. Call Sign "CENTAUR".