what would make a exhaust manifold glow bright red in a 1986 chevy caviler

An engine that runs extremely lean or extremely rich will do this, as well as a bad catalytic converter. Retarded timing can also cause this. Under no circumstances would I continue driving it. You might have 1) bad catalytic converter, 2) a bad sensor (lean/rich fuel mixtures might be due to a bad oxygen or MAF sensor), or 3) the timing is off. I'll assume since you make no mention of the car running badly that there isn't anything obviously wrong with the engine so eliminate the timing and bad sensors as the culprit, it is most likely a bad catalytic converter. However check all your sensors and intake system are good/clean as an improper fuel mixture can prematurely ruin a catalytic converter. PS: a sign of a bad cat is a rotten egg odor.

your catalytic converter collapsed.. is the engine running cold? = bad coolant thermostat.