I'm trying to get the old distributor cap off, but the three phillips head screws that hold it in place are badly corroded and don't move at all. I don't really want to risk stripping the heads, they may never come off. I've hit the screws with a shot of WD40 about four times in the last 2 days and have tapped gently with a hammer on the end of my screw driver to try and loosen them up, but no go. Any suggestions?

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Jason Priest
1986 420SEL