Heater valve location

This weekend I am finally installing a heater. The valve for the heater core..........does it really matter which hose it goes in? Inlet side or outlet side?

 

preferred is inlet side
you want to shut the hot water off before it goes inside
otherwsie, your core is always hot and will radiate some heat when not needed
some heat will transfer from the outlet side anyway

 

Thanks

 

OK, my '56 had the valve on the rear on the head, is that the right place? Seems like I've seen them elsewhere too.

 

I have valves on both. used ball valves on pipe instead of the screw type.