i was recently assembling the 302 for my z and noticed that on the top of the block behind the intake there is a hole about 1 1/2 inch in diameter and to the left of it there is a 3/8ths threaded hole. what is this used for? this is not the hole for the distributor, the intake does not cover it. usually there is a smaller hole there for a oil preasure line. any ideas?