Heat Riser Removal??? ... 68-70 340 HP Manifold

I have done several to my cars and trucks over the years.Not much cold weather driving out here. The best way is to remove the manifold from the block.Cut away the parts from the outer manifold, apply something like PB Blaster to the shaft that is left and see if it will start to move. Apply some heat if necessary.Once removed drill and tap and install short bolts where the shaft was.Or install all new replacement parts.