when i replaced my heater core i ripped the left side duct vent is it a big deal and will the heat melt any wiring.thanks

 

Generally it takes alot of heat to melt the insullation off of wires. Probably more than the heater is capable of producing. Most wire I have played with is usually rated to at least 125 degrees C, which is around 250F.

You should attempt to repair your damaged hose considering winter is coming up and we went from 70 degrees to 28 here in the desert in less than a week. A prime candidate would be dryer vent hose from any hardware store, You should be able to find a size fairly close, I think 3" is common for dryer hose but I am not sure what size is in the dash as I have never dived that deep into a first generation blazer, I believe my second gen uses molded plastic for the ventalation system. Depending on how big the rip is you may be able to get by with some aluminum duct tape, which is meant for high tempreture applications.