Hey guys so I'm trying to put new doors on my 78' 280z coupe. But I can't because it's hard so Iim trying to remove fenders for Easter task plus I'm restoring it so I'm getting rid of any rust I have so 2 birds one stone but I can't get these two bolts off can someone tell me what I can do I know it has nuts on the bottom but i cant see them and idk what size they could be. This is all stock 280z. Thanks guys this is my first project and one of my bucket list cars so sorry if I'm asking noob questions 

Try some liquid wrench penetrating oil.

 

I used a impact driver on 3 of mine and one would not come out so I drilled and used and easy out. Good luck

 

I have used half a can of wd-40 And nothing 

wd40 doesn't work as good as "Kroil" or "PB blaster". An impact screw driver would be my tool of choice. After that I switch to cutting tools and taps. They can be very hard to get out. The nuts on the bottom are welded to the cowl...

As Patcon says, a penetrating oil is best.  WD40 is a light oil for displacing water (WD = Water Displacement).  A penetrating oil has a penetrating fluid that weeps into the threads and carries the oil with it. A 50:50 mix of ATF and Acetone is a good home-brew.   I like Liquid wrench over PB blaster.

 

If you have a high current/wattage soldering iron you can place it on the head of the bolt and heat it up for 10min then cool with the penetrating oil to break the crusty corrosion.

Edited December 30, 20178 yr by 240260280

Hey guys thanks for the tips, I was wondering think if I weld on a bolt on top it will work on top of the oil?

yes, that will work.  The weld heat will break the corrosion.