1986 Chevy C10 SWB Step Side

[aotte1]

Today worked on removing pass side exhaust manifold, got 5 of 6 bolts out easy, however, the 6th one is still mostly in the head. Have got it out maybe two turns over the whole day. It will turn a little bit then tighten up. I stop, rotate it in and out a few times let it set for a while, with corrosion X sprayed between flange and head. After a while it will turn maybe a 1/16 to 1/32 of a turn more before tighten up again. Not sure what it is doing maybe galling?? Taking it slow to not break the bolt.