well.... time to pull it apart
picture for posterity (and to remember which line goes where)
and to know where the distributor was when pulled
not a terrible space to work
no smoking gun... but the center (4,6) got hot and there is some erosion.
the erosion
all signs (including rust on the spark plug threads) point to number 6 being the issue... but look at 8 - nice and steam cleaned...
and the spark plugs - rich and a bit late timing... oh and a bit of oil on number 2
but look under the exhaust valve for #6.... that looks like moisture got in there
so the question of the century... pull the other head? sleeping dogs and all of that - but it would be annoying to put it back together then start with problems.... a reminder on these heads - they came from PF1 when I went to aluminum heads. They came with the car and were "new" - they were clean and unpainted - but I've never see a head fail in less then 10k miles... yet here we are.... granted, they were also on the motor that had a cracked cylinder (number 8 was the issue there)....
I suspect it'll cost about the same to fix this head as to have another set assembled and cut down for the higher lift...
and I'm going to the Rubicon in September (hard to believe it's been 30 years since I last wheeled it)... so it needs to be stone solid.
and I may have just answered my own question... but feel free to post your thoughts.