Is this on the driver side, by the oil filter? If so, it is the location for the oil pressure sending unit on some cars, but not all. You can remove, and seal the plug with teflon tape, or any number of sealants.

Adam's Apple .... I beleive so. It's just below and right of where the distributer sits if your standing in front of the car.  It's good to know that we can remove it and reseal it with some teflon tape.  Oil leaks are not acceptable

Joel was talking about the fitting down by the oil filter, but the good news is that yours is also an oil gallery hole, and can also be sealed.

Larry

Yup...I thought you were referring to the one on the bottom driver side of the block, but the one at the rear of the intake is the same...just a different location!
One thing tho...if you think that plug is leaking, by all means seal it. However...unless it is actually loose, it's not likely it is leaking. A more likely leak is the rear of the intake manifold, where it meets the rear of the engine block.
Another possible leak is the distributor itself. Be sure there is a paper gasket on the distributor where it fits into the intake. Without the gasket, it will likely leak a bit there.
hth