More re: Heater Hose Shut Off

A few quick questions:

(1) Does anyone know why they stopped using the vacuum-controlled heater shut-off valve in 1971? Did they work? and can/should I add one on my 1972 instead of another type (e.g., screw valve, etc.) Where did the vacuum valve mount on '71's?

(2) Now, the dumb question... which way does the fluid run through the heater core? From the intake manifold through the core and back to the pump, or from the pump through the core and back to the manifold?

Thanks!
Bill
(See y'all at Carlisle!)

Did anyone respond to your questions?
Just replaced the heater hoses on my '79. Took out what I think you call the heater shutoff valve and replaced it with a ball valve. I have it in the off position. Want to see if the the excessive heat in the interior is from the engine compartment or the heater core.
The valve I took off was on the 5/8" hose and not mounted anywhere. The vacuum hose was not attached. Haven't found out where it's supposed to go.
Hank

I see this has been a well dicussed topic. no need to reply. next time I'll spend a little more time reading before I ask questions.
Hank