To add to what RW said, it will also allow the oil band to "pee" oil pressure right out, opening the "door" for catestrophic failure.
It is also a mistake to use solid Chevys in the Pontiac. Comp now offers "800-16" as a solid lifter with the oil hole drilled in the bottom, and recommends them for certain Chevy applications. They are a true Pontiac lifter. We use them in Chevys when a "small base circle" cam is used, for the same reasons one doesn't use standard Chevy lifters in the Pontiac. NEVER use the AT-992s in a Pontiac...