Heater Core Bypass Question With Twist

[B Red Dodge]

Reference the truck in my signature...

I'm thinking about putting two shut off valves on the 3/4 and 5/8 hoses going to and from the heater core in order to get cooler air from my A/C when it's on in the summer. I don't have much faith in the blend door insulating the heater core from the A/C system in my 27 year old heater box.

I've looked for coolant flow diagrams for the 350 TBI and/or Vortec blocks and haven't had much luck in determining if cutting off the heater core without adding a bypass would negatively affect the cooling system.

Can anyone advise if I need to bypass the flow through the heater core or can I just basically kill those lines by simply adding two shut off valves?

 

[Heavyleft]

Reference the truck in my signature...

I'm thinking about putting two shut off valves on the 3/4 and 5/8 hoses going to and from the heater core in order to get cooler air from my A/C when it's on in the summer. I don't have much faith in the blend door insulating the heater core from the A/C system in my 27 year old heater box.

I've looked for coolant flow diagrams for the 350 TBI and/or Vortec blocks and haven't had much luck in determining if cutting off the heater core without adding a bypass would negatively affect the cooling system.

Can anyone advise if I need to bypass the flow through the heater core or can I just basically kill those lines by simply adding two shut off valves?

You will not have any issues. The lower and upper radiator hoses take care of the engine. I have two shut off valves on mine (one each hose) to turn the flow off to the heater core in the summer time. I don't have A/C but when the coolant continues to run through the heater core, it still gets warmer in the cab. I have a Summit Racing/Maradyne heater in my rig and the hoses will still be warm and add additional un-needed heat to the cab. Ive been running like this for 3 years now with no issues. I open the valves when the temperature starts to drop and I want to use heat again.

 

[B Red Dodge]

Awesome! Thank you!

 

[Larry]

Yeah, I started doing that back in high school on my dad's '78 K20 Wrecker without A/C. You know, the ones where the blower motor blows all the time even on a 110 degree day it is still blowing heat. Just adding a ball valve to the heater core inlet and unplugging the blower motor made a huge difference in that truck.

I do the same thing on the K10 and Burb with A/C but with just one manual ball valve in the heater core inlet. It’s just a cheap ball fitting from Home Depot. It makes a noticeable difference tho! Also a noticeable difference when you forget to open the ball valve after the first cold snap in the fall and freeze your giblets off until you pull over to open the valve