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  1. #1
    Join Date
    Feb 2013
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    El Dorado Hills, CA
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    Advice needed regarding thermostat for LS3

    If anyone out there has advice and experience on thermostats for LS3's, I can use some help. I have an Edelbrock water pump that when installed stated I needed a GM#12600172 thermostat. This thermostat (185 degree), comes as a 2-piece unit meaning it's the thermostat and the housing. My engine is running warmer than I would like (up to 210 on cool days), so I'm concerned when summer comes here in California. I have a large radiator from Autorad with twin electric fans so should have plenty of cooling ability. I'm not sure what the fans are set at in the ECM but will check when the car gets tuned again this coming week. (I believe they are coming on at 190, if not, I will have them set at 190 unless otherwise suggested).
    My real question is; does anyone have a part number (and manufacturer), for a 180 "high flow" thermostat that is a direct replacement for my GM thermostat? And yes, I did contact Edelbrock but they were no help. I'm trying to get a response from Mr Gasket and/or Lingenfelter but no response yet. Thanks a lot!



  2. #2
    Join Date
    Apr 2001
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    My hunch is that the problem is not related to the thermostat, or that you even have a "problem." Stock thermostats are 187 degrees and LS engines like running a little hotter. I believe a stock tune will turn the fans on at 205 and shut them off at 195. So if you are seeing 210, that seems pretty normal.

    I wouldn't go changing parts yet. See how it all work sin the summer and take it from there.

    I would check the tune for the exact temps for the fans. I would also make sure you have a big radiator and adequate fan capacity. Feel free to share what components you are using.

    Andrew
    1970 GTO Version 2.0
    1967 Cougar build
    GM High-Tech Performance feature
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    "You were the gun, your voice was the trigger, your bravery was the barrel, your eyes were the bullets." ~ Her

  3. #3
    Join Date
    Feb 2013
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    El Dorado Hills, CA
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    Andrew, thanks for responding. I have an Autorad system that has a wider than normal radiator in their aluminum core support (about 5" wider than stock 69 Camaro). It has a 12" and a 14" fan built into their aluminum shroud. It's a very nice set-up. I only have about 200 miles on this car and it has a 418 cu in LS3 with 11/1 compression. Not big HP, only about 550. My first 150 miles it never went above 200 but it's now hitting 210. It got to 230 last week but discovered I had air in the system due to not having water in the recovery tank causing the radiator to be about 1.5" low in the top tank. Thanks again!

  4. #4
    Join Date
    Apr 2001
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    Quote Originally Posted by cwmusser View Post
    Andrew, thanks for responding. I have an Autorad system that has a wider than normal radiator in their aluminum core support (about 5" wider than stock 69 Camaro). It has a 12" and a 14" fan built into their aluminum shroud. It's a very nice set-up. I only have about 200 miles on this car and it has a 418 cu in LS3 with 11/1 compression. Not big HP, only about 550. My first 150 miles it never went above 200 but it's now hitting 210. It got to 230 last week but discovered I had air in the system due to not having water in the recovery tank causing the radiator to be about 1.5" low in the top tank. Thanks again!
    LS engines will definitely overheat if there is air in the system. They are also hard to purge.

    I've had great success backfilling the cooling system through the steam vent hose. It is a little tedious and time consuming, but it is very effective. I just take a 2" hose, connect it to the steam cross over pipe, use a small funnel, and start filling. It takes a while, but I found this method displaces any air that you might have in the system.

    Andrew
    1970 GTO Version 2.0
    1967 Cougar build
    GM High-Tech Performance feature
    My YouTube Channel Please Subscribe!
    Instagram @projectgattago

    "You were the gun, your voice was the trigger, your bravery was the barrel, your eyes were the bullets." ~ Her

  5. #5
    Join Date
    Mar 2008
    Location
    Chicago suburbs
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    What is the idea behind "LS engines like to run hotter"? Wouldn't a cooler engine make more power? I'm asking because my LS3 runs closer to 170 but I'm open to running it hotter if there are benefits.

  6. #6
    Join Date
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    Quote Originally Posted by another69 View Post
    What is the idea behind "LS engines like to run hotter"? Wouldn't a cooler engine make more power? I'm asking because my LS3 runs closer to 170 but I'm open to running it hotter if there are benefits.
    If it's not broken, don't fit it...LOL

    Andrew
    1970 GTO Version 2.0
    1967 Cougar build
    GM High-Tech Performance feature
    My YouTube Channel Please Subscribe!
    Instagram @projectgattago

    "You were the gun, your voice was the trigger, your bravery was the barrel, your eyes were the bullets." ~ Her