I've done some research on certain cylinder heads missing a mounting point for the serpentine belt.

I've heard this can be remedied by simply drilling and tapping the missing bolt, but I'm a bit skeptical of doing so.

To what depth should this hole be drilled? Is it the same depth as all of the other accessory bolt holes? I don't want to go too far and hit a coolant passage.....I'd rather have the head off and on a mill when I perform this, but its daily driven and the engine is already together and installed.

 

If you have at least one one in the head that the serp bracket can connect to, you'll be fine without drilling at all, as there will be two holes in the block also for that bracket to connect to, and thus you'll have 3 mounting points for that bracket.

 

I don't know how comfortable I am with that....Considering the one bolt you mention is torqued down and the other on the bottom of the block is as well, and I can see the bracket flexing when throttle is applied. I'd rather secure the A/C and smog pump bracket the way it was intended. I'm guessing it couldn't be more than half an inch in depth.

 

Why not just measure the depth of the existing hole and do the same?

But like already said, that hole is not strictly necessary. Lots of guys leave it alone, and without issues.