same thing happened on my boat, only way to get it out was to use a very small carbide bit in a dremel and cut around the ez out then use a slightly larger one. if you can't see it ,don't bother you'll just trash the head. why is pulling the head not an option ? it may be the only option. if you replace the heads, you have to pull 2.

 

Welp, used a dremel and it got most of the drill bit out. Tried another EZ-out and snapped it off too. That was enough fun for me. Put the new manifold on and said to hell with the back bolt. The truck is running again and no leaks so far. If my brother wants to pursue it any farther, he can...I'm done with that POS.

You guys should have seen the cracks in the old manifold. It was really close to breaking into 2 pieces. There was a chunk about the size of a paperclip broken out of it. It sounded real nice.

 

one of mine had a nice crack in it at about 20k when i put my headers on. did'nt even know it until i pulled them. your bolt may have been cross threaded from the factory, which would make it extremely difficult to remove. sorry that did'nt work out for you, hopefully you won't blow that gasket out after a few thousand miles. if it does i hope you used antisieze compound when you reinstalled the bolts. you might be ok if the headers have a thick flange. e

 

If Im doing headers I always pull the inner fenderwell off,do you have it off?

 

Both of the back exhaust manifold bolts on my dads old '99 6.0L were snapped off, never had any leaks though.

 

Yeah gonzo, had to wash about 20 pounds of mud out from the fenderwell before I took it out. Jacked up the front end and took off the tire. That's the only way to fly.

 

Dude I feel for ya, I did the same damn thing but I did manage to use a carbide drill bit and that drilled a new hole but... I broke the mother off inside the hole so now i'm as fuct and you are but I think i'm one a head of you as I broke the dipstick tube in the block then went to get it out and the mother fell inside the block.

 

i've worked in mufflers shops for 20 years, do it all the time.
if you can't get it out... find some oooold guy in a muffler shop with no fear.
1. weld a nut on top of the broken stud and try to turn it out with a wrench/socket.
if that fails..
2. put a bead of mig weld on top of the broken stud and then get it red with a torch, then hit the oxy handle on the torch and blast it out of the hole.

don't laugh, i've got a guy in my shop that does step 2 so clean you don't even tap the threads, acquired skill and not for the faint of heart, especially with aluminium.

if that fails, might as well do some upgrades while you have the heads off
good luck

Dave