Hey I'm a happy Guy. My mechanic and I have been chasing a front right intermittent noise and rebuilt the torsion bar,replaced upper and lower ball joints, tightened all the body mounts and numerous other things including new shocks, Then I joined the Blazer Forum and read where it could be the hood hinge. Today I put a piece of 3/4" weather stripping between the hood and the fender voila the damn noise is gone.
I wish I could remeber who wrote the post but whoever you are THANKS I was going nuts and spending like a drunken sailor.
My Blazer works great at 170000 km. and I'm in sales on the road most days.

 

Not tooting my own horn, but it probably was me. There is a TSB (technical service bulletin) about this issue. The fix is to put a set of conical washers between the head of the bolt and the hinge. GM part number 12383460. Shouldn't cost more than $4 from the dealership.