I am trying to find out if it is under the hood or under the dash...and where to look.Can anyone please help me out?

there is no such thing as a heater core valve

hey dude go to automotiveforums.com, but l think its behind the center console thats where the heater core was on my old z28 hope this helps

on most all cars and trucks they are under the dash and a pain to replace

There is not one.

On the v8 there is a flow control valve located on the heater hose inlet assembly. It is not like older coolant flow valves. If you are looking for the heater core itself, it is under the dash passenger side.