Caution! Caution!,,
Matt, this sounds like the hinge pin for the timing chain tensioner arm. Do NOT try to start the engine if this is the case. Take your valve cover off and make sure the tensioner arm is intact.
If this is the case, someone has used the wrong bolt to hold the bracket. Normally a very short 19mm bolt threads into the block and not the threaded pin.
Joe Alexander
Blacklick, Ohio