Head Gasket Headache

I need some help here guys,
55 CJ with a f-head. I can't keep head from leaking. Coolant is escaping through exhaust. There is no sign of it getting into the oil so far. I took the head to a machine shop and had it checked out and they gave it a clean bill of health. it is always to the #4 cylinder or #3 I took the head off and no signs of damage to the gasket. Last time I retorqued the head bolt after two weeks and 4 weeks of running the motor and it failed on the 5th week. I am not thinking a crack in the head or block because it does fine for a month or so ??
I appreciate any help I can get on this.

 

You actually check the block for cracks? Fairly common in the #3 exhaust valve area, if the coolant ever froze.

Also the top face of the block should be checked for perfect flatness. I presume the head was...

 

magna flux block and head at machine shop?

 

head was checked , I will check the block once I get a flatedge. I doubt coolant freezing... it has been a Phoenix Jeep for at least the last 25 years .

 

That is my next step. I didn't want to do a complete tear down, but at this point i see no alternative.

 

Just a thought, and hopefully the more experienced will chime in but, any chance that new head bolts might resolve the issue. Just thinking that, if the bolts have been used several times, i.e. torqued and re-torqued and re-torqued, maybe some are weak or stretched or something.