LSx can you safely install a valve in the hot side heater hose?

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Id like to install a valve in the hot side heater hose or better yet both hoses so the heater box in the cab is not broiling hot in the summer months. I don’t want to use the 4 hose bypass valve. Can we safely block flow to the heater core or does the stat demand hot flow across the element?
Planning to run a 175 stat . LQ 4
 
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Not saying you can or cannot but I would be hesitant to block off the heater core. Some engines rely on this flow to allow the circulation of the coolant during warm up to eliminate hot spots. Usually the heater hose come off near the thermostat so that the flow to the heater core passes by the thermostat transferring the heat of the engine to the thermostat. You would only need one shutoff valve, just monitor the way the engine warms up if you install one.
 
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I did that on the F-450 in my sig with a coolant filter in between the 2 heater hoses-the valve is closed in summer,forcing coolant through the filter, and open in winter, which allows coolant through the core (but some likely still goes through the coolant filter, still gets hot). If you put 2 valves in, one connecting the 2 hoses, one blocking the core, and opening/closing them to direct the flow, it wouldn’t hurt anything.
 
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Id like to install a valve in the hot side heater hose or better yet both hoses so the heater box in the cab is not broiling hot in the summer months. I don’t want to use the 4 hose bypass valve. Can we safely block flow to the heater core or does the stat demand hot flow across the element?
Planning to run a 175 stat . LQ 4

It needs flow to operate properly, GM used 4-port heater control valves on Express/Savanna Vans....If they could've saved a penny a vehicle by using a 2-port control valve....They would've.

I tried to run a 2-port on my '85 C20 Suburban with a LM7 5.3L....The coolant temps would have weird swings. I installed a 4-port & cured the issue.

The 4 Seasons valves are trash, Use GM# 12380318. You can use a Micro Switch/Toggle Switch & a Secondary AIR Solenoid GM part# 1997212 to control the Valve.
 

P10crew

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Cline have you ever did the drill a 3/16” hole in the back wall deal?
To get some hot flow across the stat some have had success drilling a 3/16” hole at 9 o’clock in the back wall inside the stat housing.
I have studied the ls water flow throughout the motor and pump and I have no clue why they did what they did . Just stumped why they didn’t put the stat on the outlet of the motor.
 

P10crew

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Cline do you know if gm used some sort of a bypass on the gen 3 trucks that didn’t have rear heat? Or did they just let it circulate through the heater core?
 
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Cline do you know if gm used some sort of a bypass on the gen 3 trucks that didn’t have rear heat? Or did they just let it circulate through the heater core?

The only LSx equipped vehicles to have a Heater Control Valve is the Express/Savanna Vans that I know of anyway. All the GMT800 & GMT900 Trucks/SUV's just straight circulate through the Heater Core/s.

I believe this was because the GMT800 was a clean sheet design where the HVAC module was designed in such a way where a Hot heater core didn't affect A/C performance.
The Express/Savanna is a Legacy platform dating back to 1996 coupled with limited space....Needed a heater control valve to keep the Hot core from affecting A/C performance.
 
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You can only do this if the engine has its own bypass incorporated like your old fashioned small blocks that bypass from the intake manifold to the water pump when the tstat is closed. These engines do not and rely on the heater circuit for circulation when the tstat is closed.
 

P10crew

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The Stats have a built in bypass and fairly large bypass holes. Also when installed the rear most bypass portion of the stat does not sit tight against the back wall. As the stat opens the bypass passage is sealed off by the rear portion of the stat. You would think that the (4) 3/16 bypass holes in the stat would be enough to keep the element buffered some but apparently it’s not enough hot flow.
Seems to me like a very poor design to send the hottest coolant in the motor right back into the inlet side of the pump via the heater circuit regardless of wether the stat is open or closed.
Cline thanks for the info on the truck config. I have pulled several donor LQ ‘s at the salvage yard and like you say none of them had any sort of external bypass visible in the motor compartment. I’m not sure how I’m going to address this as I convert the pumps to AN heater circuit plumbing and the reduced inner diameter of the Teflon hose won’t fit over standard size hose barbs such as what’s on the 4 hose bypass valve.
Thanks for the replies.
 

P10crew

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CLine will a 12597567 work in place of the 1997212?
I’m having trouble sourcing locally.
GM says the 1997212 is discontinued and the acd 214-358 shows no stock in the warehouses.
Summit shows stock on it but if the 12597567 will work I’d get that locally.
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More like 5/32", Don't hold me to that though as I use Bulk vacuum hose to make the connections & just use what fits.....It's way smaller than 1/4".

That's why I like to use the 1997212.....Cause no adapting is required.

Try GM# ‎14102002 (EGR Vacuum Regulator), Only downside is the old school Metri-Pack connector vs the Delphi 150 Series.
*One nipple will have a foam cover.....That's the Vent/Bleed. No hose connects here.
*The nipple next to the Vent will connect to the Control valve.
*The nipple on the opposite end connects to the vacuum source.
 

P10crew

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I can just call summit and get the 1997212 coming. How does the 7212 cent bleed?
 
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