heater hose diaphram on inner fender

[Westtexdart]

1972 Swinger,pulled 318 with a.c and 904 out,went in with 340, 727, no air.I've seen pictures of some with the heater hoses going through this vac. actuated diaphram,and some with hoses mounted directly to heater core. Whats the difference ?Thanks for any help.

 

[ted_sweet]

only a/c cars had the valve, on non a/c cars coolant always goes thru the heater core.

 

['64 Cuda]

The vac. valve shuts off water flow through the heater core when the heater isn't being used. That way you don't have hot water in the core working against your AC evaporator in the same housing under the dash.