I have headers to put on my 390, but the manifold bolts are frozen in the block, the top #6 bolt is even broken. How can i get then unstuck without breacking them and having to retap the holes?
Thanks--Nick

 

Take a torch and heat head until cherry red around bolt, while having a pair of vicegrips on the head of the bolt. when heated remove vicegrips and apply wrench and slowly rock back and forth until it will move freely. take it nice and slow. also be careful. If you know that the old exhast manifold is toast you can you can take a big chishel and carefully tab on each section and it will break up really easy, but of course undo the four bottom bolts first. this will let you better access to the bolts. Also if anything left sticking out of the old broken one. heat up and take out with vicegrips