whats the rectangular hole in the center plater right under the intake ports

 

Its an air induction hole. The air pump pumps air through there via the air control valve /intake manifold then out the 1/2" holes that you see in the exhaust ports. If your car fails smog when everything is mechanically sound.. its likely that the 'hole' is clogged up with carbon.

 

hmm
so thats why my engine bay noise id so much higher since i put the '79 intake on

guess ill have to figure out a way to block it off or something