HELP! Black insulating material coming out of A/C Vent
 

While driving 84 Carrera w/27k miles yesterday, A/C on high, all of a sudden, black insulating foam like material blew out of the rh center vent and all over my wife's lap.
What the heck is it? A/C continued to work fine.

The remains of sealing foam from the interior of the evaporator - it is harmless. Common given the vintage of these cars. The foam disintegrates due to time. The evaporator will be very slightly less efficient due to some air bypassing the evaporator fins/coils but that's it - it won't likely damage the A/C having this condition. The only problem I can fore see is the crumbling foam clogging the condensate (water removed from the air by the A/C) drain in the bottom of the evaporator housing but if that happens the drain can be cleaned out with a stiff wire/vacuum cleaner from the bottom of the car.

Black Insulating Material
 

Thanks Jeff!