Originally, there would have been a vac. line from the carb, up to the thermal valve("temp sensor"), and from there, another hose to the air door/diverter valve("vac motor"). If you still have the emissions decal on the firewall, it should have the diagram for the stuff...I think. I'm not sure when they actually started putting the emiss. vac line info on the decals....it may have been later than '78.
If the thermal valve is gone, then the diverter door ain't working anyway, so just remove the hose you have left. Make sure the door in the air cleaner housing is OPEN, too. They sometimes get stuck in the warm air position, so if you have the metal hose from the exhaust manifold to the air cleaner, you're getting hot air into the intake all the time.
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Joel Adams
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