I've tried several penetrant including the 50/50 ATF + Acetone. So far it won't budge. I have tried heating it up with a torch, but not a lot as I'm scared I'll damage something. Need some advice. Is it safe to apply heat to it? How hot & how much. I think the penetrant isn't getting down into the threads, maybe too tight. Tap with hammer + heat? Any tips or tricks? Thanks.