What could it be no heat

Having problem with my 67caprice heating.
Started the car let it warm up for about 30min.
Turn heat on only cold air,I hear fan working  and air is going from ducts vents
Temperture is on hot. I open hood and touch the top hose it was hot also heat hose too
One from the water pump was warm the other was cold  
looking for some hints on this cold caprice?  

Sounds like maybe a plugged heater core. Not real familiar with the old Chevys. Is there a control valve that may not be working?  

sounds like it a heater core problem. before you spend the money and the hasel of replacing it, try to take the heater hoses off and flush the core untill you see good flow through both sides. if the still is no heat then the vacume flap that is under the dash is not working. maybe a vacume leek in the dash somewhere.  

I open the hood to look for a control valve, there isn't one I also look under the dash   the flap work by cables
I move the heater controls levers everything move  ok  

If your car doesn't have factory A/C, then I don't think it'll have a hater control valve.

The previous suggestion is good, disconnect the heater hoses at the core, then use a garden hose to try and flush out the heater core. If the water flow is poor or extremely dirty, then I'd suggest replacing the core.  

You guys are right,it was the heater core I put a water hose nothing came out at first but metal parts with dirty pour out.

guest i put in a heater core, i got a price around $60 dollar for core

Thank You !