Classic/Antique Car Repair: 1953 Chevrolet, heater hoses, heater core

Question
My 1953 Chevy heater stays hot in summer, I assume the valve to close heater core is broken. I plan to put a shut off valve in the heater hose. Does it matter which of the 2 heater hoses I put it into? If it does which one should I put it in? how do I determine which is the input or output hose?
Thanks
Dennis

Answer
There are two hoses to the heater. One comes from the engine block and should be the smaller of the two. the larger one is the return and goes to the water pump. the shut off should be in the smaller or feed hose. That way hot water will never reach the heater core when shut off.