Join Date: Jan 2015
Location: Injun Territory, 'Merica!
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For over a decade, I pulled 6X-4's & included them with generic code 400 shortblocks selling them to a major Pontiac engine builder. In the yards, I always popped the original ex man bolts, good, with my mini sledge jarring the threads slightly before carefully removing the ex man bolts with a long ratcheting breakover. Never broke an ex manifold bolt this way. During this time, also picked up loose heads from storage racks in salvages and from two monster engine core businesses. Some of these heads did have broken ex bolts. Broken exhaust manifold bolts can be drilled out, but it's a ton easier, with perfect results, when the head is off and at a machine shop. My machinist had a quick asm fixture he used on his drill press to do this. In your shoes pull both heads, take them to a Pontiac savvy shop, have the 46's treated to a good valve job, consider milling the head's slightly, and have the bolt properly drilled out, this would easily save wallowing the hole out and having to mess with a helicoil.