Not sure what engine we're talking about here, but on my '68 L6 292 there's one hose from the valve cover [forward drivers side] to the air cleaner. This one provides fresh air to the engine, as filtered thru the air cleaner. There's another 3/8 hose that comes from the PCV valve in the rear of the valve cover to the 3/8 PCV input on the front of the carb. This one puts vacuum to the PCV and sucks air out of the engine. Both of these hoses have to be connected for the engine to breathe right. It's a circuit. It may have some bearing on your over heating.
