PB Blaster works. You want to spray it until it pools on the floor. Then every few hours or so use a small ball pein hammer and give it lateral "taps" around the clock (as in do 1 o'clock, then 2 o'clock, 3 o'clock, etc) More PB Blaster as you go along.
Then finish it up by giving it a good strong tap "in" on the exposed square. Did I say more PB Blaster?
And yes, you can grind flats on it to help turn. I've found that an impact wrench with a true "square" drive (no 12point pretending to be 4 point) will remove almost anything square.
Do this for a week. If no satisfaction THEN try heating the adjustment wedge only (NOT the backing plate casting it turns in) with a torch and let it cool. Then start the round the clock again.
You should be able to turn it in (clockwise) to the point where it "pops off the cap" which covers the wedge. If you get to the point where the wedge is loose and now just turning - you can give the exposed square end a whack with the hammer and remove the cap that way. (It will fly out across the garage and hide under something heavy.)
You can put it all back together with a NEW wedge and put the cap on and pein the cap seat area edge to hold the cap in place. I've also found you can gently "unbump" the cap a bit to make it fit more snug. (the act of removal tends to increase the dishing and reduce diameter of the cap.)
Joe K
