Heater Hose Routing
- Thread starter Jtobe81
- Start date
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Rustisbest
Full Access Member
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- Jul 20, 2021
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- Location
- Athens, TN
- First Name
- Matt
- Truck Year
- 1979
- Truck Model
- C10
- Engine Size
- 377
5/8" hose from the intake to the lower heater core inlet
3/4" out to the pump or the radiator
3/4" out to the pump or the radiator
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- Downingtown, PA
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- Wayne
- Truck Year
- 1974
- Truck Model
- Jimmy
- Engine Size
- 350
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projo198
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- Jan 14, 2025
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- Location
- Lawson MO
- First Name
- James
- Truck Year
- 1978
- Truck Model
- K10
- Engine Size
- 350
I just did this, and it changes between models and transmissions.
My '78 K10 is a manual and stated smaller bottom heater hose (5/8 pushing coolant to the heater core) from the intake manifold and larger top return hose (3/4) straight back to the water pump.
I think it would work either way, but my own radiator does not have a port where the diagram above shows one.
Lastly you may consider a 5/8 ball valve for shutting off the flow during the summer to avoid excess cabin heat. You'll need to order one though, 5/8 is not a commonly used valve size found at hardware stores.
My '78 K10 is a manual and stated smaller bottom heater hose (5/8 pushing coolant to the heater core) from the intake manifold and larger top return hose (3/4) straight back to the water pump.
I think it would work either way, but my own radiator does not have a port where the diagram above shows one.
Lastly you may consider a 5/8 ball valve for shutting off the flow during the summer to avoid excess cabin heat. You'll need to order one though, 5/8 is not a commonly used valve size found at hardware stores.
