Hi again all. So I went over to a friends house as he offered to show me how to get to the EXUP valve and grease it. I'd have done it myself, but I didn't have copper grease and he did, plus it's easier with some help. Two heads and all that. We get the cover off fine, and I start with the second set of 3 bolts. They've been changed before, as the bolt heads are different sizes. One came out fine and the second was giving me a bit of trouble. While trying to ease it out I heard/felt the dreaded 'snap' of the bolt shearing. Damn. So I moved on to the third which was even more stuck, and the same thing happened.
The two bolts that sheared are the ones that hold the cable bracket in place. I've since put some spare bolt in the holes, and a plate to hold them in place, so at least the cable bracket won't move around too much, but I'd like to sort it out. The current state after having tried to drill out the bolts, is that both bolts are flush to the exhaust, one has an ez-out embedded in it (very hard metal, tough to drill) and the other has a tap and die bit in it (also very hard to drill.)
I've sort of made a mess of it I know, and while one sheared bolt is solid and shouldn't be too hard to drill out with a good bit, the other that has the tap/die bit in it is hollow part way through, with parts of the centre hole filled with said bit. This means that if a drill bit snags somewhere it will snap. So before I go and snap any more bits (already snapped 3) I wanted to look for advice.
I've seen a few methods for removing sheared bolts, such as welding a nut on, drilling with a left hand bit etc. but most of these won't work. I could try taking off the downpipes to make it easier to get to, but now I'm worried about more bolts shearing as the downpipe bolts go through a similar cheesing process to the EXUP bolts don't they?
Another thing I wanted to ask is are there any stronger bolts available that would better resist the heat from the exhaust? Maybe parmesan instead of cheddar?? This is just going to keep happening otherwise, and while it's good being able to practice drilling bolts it's not ideal. And I don't want to leave the EXUP to seize.