93 vette no heat. the lines are hot but no heat

Could be a partially obstructed heater core, or more likely a vaccum connection for the blend doors or the inside temp switch that keeps the vents from opening until it heats up, so as not to blow cold air on the driver. GM has used a system like this for many years. Often times the problem you are describing results when that sensor no longer detects the temp as it should.

DID VETTE COME FROM A SOUTHERN STATE? IF IT DID, SUSPEST AN OBSTRUCTION IN THE HEATER CORE ITSELF.HAD AN ALLANTE FROM VERO BEACH,FLA.DIDN'T USE HEATER AT ALL AND PROBABLY NEVER FLUSHED SYSTEM,HAD TO DRIVE VEHICLE WITH HEATER ON HIGH ALL THE TIME TILL A CHUNCK OF DRYED UP ANTI-FREEZE FINALLY DIS LODGED IT MAY BE BETTER TO REPLACE HEATER CORE.