1983 Z-28. 305 Crossfire Injection. 61,500 miles on it. Car is running fine, not overheating. But I do have a pretty good coolant leak. It seams like its coming from the back of the engine. Could it be the heater core? Only leaks when the car is warmed up. Seems to be only coolant, no oil.
Its just bad timing for a issue to arise. I'm putting her away in storage today for the winter and won't be able to get to her till spring.
If not the heater core what else could it be?

 

Not the heater core. That isn't on the back of the engine; it's in the interior. When it leaks you get a green lake for the passenger's feet. Therefore that proposed "explanation" doesn't make the cut past my signature. Read that (my signature) for helpful troubleshooting advice.

More likely, intake gasket; freeze plug; or heater hose fitting if that's back under the distributor.

NOT likely to be a head gasket or cracked casting but of course not impossible... just not at all likely.

 

You can use a dye additive and a UV light to find the source.
They sell kits at Auto Zone, etc. for under $20.00.