You may be able even try this from the topside since that hole is open to the valley. Using a drill keep stepping up in drill size drilling the center of the bolt using plenty of PB blaster. After a few holes it gets hot enough to suck the lube in and break free. The good part is even if drill doesnt get it you now have a weaker bolt with a hole in it to use an extractor. Just did this on a broken motor mount bolt. Weld kept breaking off. But the drill did the trick.


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