usually the original shut off was located between the heater core and the engine block. it kinda looks like a crooked letter "P" with one hose going in and another going out, with a small vacuum line somewhere in the middle.... was not one of GM's best designs, and typically they stopped working and were usually taken off or replaced with a gate valve of some sorts... or some of us would just disconnect the hose all together and route it back to itself on the core, and the other hose from the pump to the intake..... of course when colder weather comes around, would have to route them properly to get a little heat inside...
here is a picture of the control valve...hopefully,
StingrayJim NCM Lifetime Member #1936
Stingray's '76 StingrayJr's '78 Lil Red '94 (click each one to see a bigger version)
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