1948 DeSoto bypass valve for heater core question

[CATPAL]

I have a 1948 DeSoto and the heater core puts a lot of heat into the car. The motor has been replaced with a sbc motor. I was wondering how to shut off the coolant from going to the core in the summer. There is a heater hose going to the water pump and another going to the front of the intake manifold. Would putting a shut off ball valve in one of the lines be correct? Which of the two lines would be the correct one? I would like to be able to get heat in the cooler weather, so I don't want to just disconnect the heater core permanently. Thanks in advance for any help.

[ted sweet]

IN  either linw

[CATPAL]

Thank you. Would putting it in one of the heater hoses still put coolant pressure on the heater core? I was thinking it would be possibly better if it didn't? Tried reading about it, but got conflicting ideas. I can get the right size valve to fit either hose.

[marcapra]

I should first say I have no idea what an sbc motor is.  I also have a 48 DeSoto and the hot water comes out of the top of the head from a shut off water valve.  I have never heard of a water heater hose connecting to an intake manifold.  How could it?, it doesn't have any water in it, unless you have a gas powered heater.  All you do on an original DeSoto is shut the valve off in summer.  AB sells the shut off valves for $18.  

 

 

Edited July 2, 2023 by marcapra (see edit history)

[CATPAL]

Thank you marcapra for your reply . sbc= Small block Chevy.

[JACK M]

19 hours ago, CATPAL said:

Thank you marcapra for your reply . sbc= Small block Chevy.

And coolant does run thru the intake manifold on those.

[Akstraw]

Simple enough, though, as stated: if you don’t want water to flow, just install a cutoff valve.  Seems that anywhere you put it in the path, it will stop the flow.

[Rusty_OToole]

Hot water flows from the top of the engine near the thermostat to a lower connection in the water pump. Put the valve on the high pressure side or the top of the engine. The hot water is supposed to enter the heater at the bottom and exit at the top. A ball valve should be fine if it is rated for hot water. If you want a valve you can control from inside the car, Chrysler products used a cable controlled valve in the seventies and eighties. Ask your parts store for one for a 1975 Dodge pickup truck with 318 motor. They are all the same, used to cost about $12 bucks. Probably double that now.

Later....

Here is what one looks like. You can control it with a universal choke cable. The cable clamps to the flat part and the wire wraps around the pin. You can use the stock control if you have it.

 

Edited July 4, 2023 by Rusty_OToole (see edit history)

[Jubilee]

  I have a sbc in my Willys CJ5 and I have a shut off valve on both the water pump

and intake manifold heater lines. Gate valve on intake and ball valve on water

pump for ease of installation.
  I feel two valves helps slow convection heating of heater core.
 

[CATPAL]

Thank all of you for your replies to my question.

[marcapra]

On 7/3/2023 at 9:58 PM, Rusty_OToole said:

Hot water flows from the top of the engine near the thermostat to a lower connection in the water pump. Put the valve on the high pressure side or the top of the engine. The hot water is supposed to enter the heater at the bottom and exit at the top. A ball valve should be fine if it is rated for hot water. If you want a valve you can control from inside the car, Chrysler products used a cable controlled valve in the seventies and eighties. Ask your parts store for one for a 1975 Dodge pickup truck with 318 motor. They are all the same, used to cost about $12 bucks. Probably double that now.

Later....

Here is what one looks like. You can control it with a universal choke cable. The cable clamps to the flat part and the wire wraps around the pin. You can use the stock control if you have it.

 

Rusty, I just installed my Comfort Master MoPar heater into my DeSoto.  I saw a pic of a Chrysler engine bay where the hot water coming from the valve was going the low tube on the heater core and thought this was wrong, so I installed my hot water tube to go to the high heater core tube.  I based that on how my radiator works, but maybe a heater core works opposite to that?  Maybe the hot water tube should go the low tube and the high tube should go back to the water pump to keep the heater hotter?  

[Rusty_OToole]

Your radiator is based on how the ENGINE works. Some early cars, like Ford Model T, had NO water pump. They worked by thermosyphon which means, hot water rises in the engine, spills over into the rad, and sinks thru the rad as it cools, NO water pump.

 

Your heater is different. For one thing, by pumping the water in at the bottom and out at the top, you avoid trapped air causing an air lock which prevents the heater from working. All heaters, so far as I know, have the inlet at the bottom and the outlet at the top. Remember, there is no filler or outlet at the top of the heater to bleed off air.

[marcapra]

Thanks Rusty, you explained it very well.  I'll change my heater hoses then.  Thanks.  

[marcapra]

Rusty, one more question.  Which hose should I put the Prestone back flush T fitting on?  I would assume it would be on the hot water from the head hose.  Then the back flush would flush out the block and radiator.