Unfortunately while trying to torque the rear most drivers side valve cover bolt, the one next to the odd-ball larger bolt that holds a ground strap, I snapped it. I had a valve cover leak and thought tightening down the bolts would help me out. I made it all the way around the cover (bolts were fairly easy to tighten), everything was fine till I got to that last bolt. I've since removed the valve cover to attempt to begin removing this snapped bolt. The bolt is relatively flush with the head, and I managed to drill a mostly center hole into the snapped bolt with my right angle adapter.
I've done some research on methods for extracting this type of problem bolt, and most suggest using an ez out or extractor. This has failed me, but luckily I haven't made the issue any worse. Instead its left me with a mostly center hole. My next choice is to drill out the hole and re-tap it. This leads me to my two main concerns. accompanied by a few questions.
1. I noticed that some of the valve cover bolt holes are drilled substantially deeper than others. Namely there are two I noticed (not sure if my snapped bolt hole is also one). The two specifically are the front-most valve cover bolt on the passenger side, and the rear-most valve cover bolt on the passenger side. If I stick a thin punch in there, the punch does not bottom out like most of the other holes. Why are these two drilled deeper? Is my snapped bolt also supposed to be drilled as deep? Or is it the same depth as most of the other bolts I found around the perimeter of the valve cover?
2, My second question will require a more specific answer and is why I bolded "mostly" above. Preferably accompanied with some type of diagram of the engine head. I am wondering what the actual tolerances of these valve cover bolts are, in terms of diameter & depth, before I start drilling into another channel of the engine, (or cooling jacket, etc)? Alot of people suggest drilling the valve cover bolt hole larger, and then using a helicoil. So how much tolerance do I actually have exactly?
I've done some research on methods for extracting this type of problem bolt, and most suggest using an ez out or extractor. This has failed me, but luckily I haven't made the issue any worse. Instead its left me with a mostly center hole. My next choice is to drill out the hole and re-tap it. This leads me to my two main concerns. accompanied by a few questions.
1. I noticed that some of the valve cover bolt holes are drilled substantially deeper than others. Namely there are two I noticed (not sure if my snapped bolt hole is also one). The two specifically are the front-most valve cover bolt on the passenger side, and the rear-most valve cover bolt on the passenger side. If I stick a thin punch in there, the punch does not bottom out like most of the other holes. Why are these two drilled deeper? Is my snapped bolt also supposed to be drilled as deep? Or is it the same depth as most of the other bolts I found around the perimeter of the valve cover?
2, My second question will require a more specific answer and is why I bolded "mostly" above. Preferably accompanied with some type of diagram of the engine head. I am wondering what the actual tolerances of these valve cover bolts are, in terms of diameter & depth, before I start drilling into another channel of the engine, (or cooling jacket, etc)? Alot of people suggest drilling the valve cover bolt hole larger, and then using a helicoil. So how much tolerance do I actually have exactly?
