LS3 Thermostat issues - The 1947 - Present Chevrolet & GMC Truck Message Board Network

6600DURAMAX · 05-07-2023, 08:46 PM

Need a little help - have Blueprint Engines LS3 with the CVF front drive kit -

Originally installed a vintage air 186 degree (part number 707171) thermostat with a Summit - SUM-370998B swivel thermostat neck - this setup resulted in a slow drip from the bottom the the thermostat housing.

I talked to CVF as t I thought I might have the wrong setup - they said all their kits run LS1 stuff and gave me part number for Mr Gasket Housing - 2670 and the thermostat 6367 part number ( 160 degree which I actually like better anyhow )

When the Mr Gasket neck and thermostat arrive I did a better job of dry fitting it and it doesnt appear to fit?
You have to push ( or compress) the thermostat spring to get it to seat flush then it appears the gasket doesnt fit into the housing correctly ?

What am i doing wrong ?

LS short box · 05-07-2023, 09:18 PM

The stat on the left is for a LS1. The little notches near the rubber gaskets clip into the stock LS1 aluminum stat housing.
The stat on the right is for a LS3 ish engine. It does not clip into the thermostat housing.
The LS1 and the LS3 thermostat do not interchange. The LS3 thermostat is slightly larger in diameter compared to the LS1.
It really depends on your water pump. Is it a 2002 Camaro or a later model Camaro?

6600DURAMAX · 05-07-2023, 10:45 PM

Both thermostats looks very close if not the same as far as gasket size ..... neither really fit in the housing on the engine .

Its a LS3 from Blueprint engines but has a CVF front drive kit

**mongocanfly** · 05-07-2023, 11:10 PM

If its leaking around the housing, sand the mating surface to clean the finish off it.. mine was chrome aluminum..then use a good silicone sealer on it.. I swapped mine to a straight housing like you have..and it leaked before I even tried cranking the engine..tried to seal it several times before I did the above..no leaks now..

Joyridin · 05-08-2023, 07:38 AM

Around 2014, they changed the thermostat style very slightly. Most aftermarket housing show something like 2004-2018, but that isn't the case. I bought the older style and opened up the hole where the thermostat mounts by about .05". I have been running it for 7 years with the LS3 thermostat and no issues.

6600DURAMAX · 05-11-2023, 12:37 PM

Just to close this out - purchased a LS1 thermostat housing with a 160 degreee stat

Part # is LPE-L310045297

Bolts in - will fill with fluid tomorrow - If I don't update again All is good !!

LS short box · 05-11-2023, 04:56 PM

Just a tip that has worked for me. Before you install the new stat I drill three 1/8" holes in the metal flange that hold the gasket. Seems to help getting first start air pockets out of the system.

87chevy.com · 05-12-2023, 08:15 PM

the thermostat you pictured is from 2 different pumps.
theirs 3 different length thermostats, LS thermostat is not universal... its specific to the pump.

good video:
https://www.youtube.com/watch?v=2apgFAuo4Dk

05-07-2023, 08:46 PM	#1
6600DURAMAX Registered User Join Date: Nov 2000 Location: Wheatfield IN, USA Posts: 1,107	LS3 Thermostat issues Need a little help - have Blueprint Engines LS3 with the CVF front drive kit - Originally installed a vintage air 186 degree (part number 707171) thermostat with a Summit - SUM-370998B swivel thermostat neck - this setup resulted in a slow drip from the bottom the the thermostat housing. I talked to CVF as t I thought I might have the wrong setup - they said all their kits run LS1 stuff and gave me part number for Mr Gasket Housing - 2670 and the thermostat 6367 part number ( 160 degree which I actually like better anyhow ) When the Mr Gasket neck and thermostat arrive I did a better job of dry fitting it and it doesnt appear to fit? You have to push ( or compress) the thermostat spring to get it to seat flush then it appears the gasket doesnt fit into the housing correctly ? What am i doing wrong ? Attached Images __________________ 1972 K5 Build - plans - LS3-6L80e-One Tons..... 1971 CREWMAX Build.....at body shop for couple more years

05-07-2023, 09:18 PM	#2
LS short box Registered User Join Date: Jun 2015 Location: Carlos MN Posts: 1,923	Re: LS3 Thermostat issues The stat on the left is for a LS1. The little notches near the rubber gaskets clip into the stock LS1 aluminum stat housing. The stat on the right is for a LS3 ish engine. It does not clip into the thermostat housing. The LS1 and the LS3 thermostat do not interchange. The LS3 thermostat is slightly larger in diameter compared to the LS1. It really depends on your water pump. Is it a 2002 Camaro or a later model Camaro?

05-07-2023, 10:45 PM	#3
6600DURAMAX Registered User Join Date: Nov 2000 Location: Wheatfield IN, USA Posts: 1,107	Re: LS3 Thermostat issues Both thermostats looks very close if not the same as far as gasket size ..... neither really fit in the housing on the engine . Its a LS3 from Blueprint engines but has a CVF front drive kit __________________ 1972 K5 Build - plans - LS3-6L80e-One Tons..... 1971 CREWMAX Build.....at body shop for couple more years

05-07-2023, 11:10 PM	#4
mongocanfly Post Whore Join Date: May 2015 Location: Alabama Posts: 14,585	Re: LS3 Thermostat issues If its leaking around the housing, sand the mating surface to clean the finish off it.. mine was chrome aluminum..then use a good silicone sealer on it.. I swapped mine to a straight housing like you have..and it leaked before I even tried cranking the engine..tried to seal it several times before I did the above..no leaks now.. __________________ Mongo...aka Greg RIP Dad RIP Jesse 1981 C30 LQ9 NV4500..http://67-72chevytrucks.com/vboard/s...d.php?t=753598 Mongos AD- LS3 TR6060...http://67-72chevytrucks.com/vboard/s...34#post8522334 Columbus..the 1957 IH 4x4...http://67-72chevytrucks.com/vboard/s...63#post8082563 2023 Chevy Z71..daily driver

05-08-2023, 07:38 AM	#5
Joyridin Registered User Join Date: Sep 2020 Location: Cleveland, Ohio Posts: 478	Re: LS3 Thermostat issues Around 2014, they changed the thermostat style very slightly. Most aftermarket housing show something like 2004-2018, but that isn't the case. I bought the older style and opened up the hole where the thermostat mounts by about .05". I have been running it for 7 years with the LS3 thermostat and no issues.

05-11-2023, 12:37 PM	#6
6600DURAMAX Registered User Join Date: Nov 2000 Location: Wheatfield IN, USA Posts: 1,107	Re: LS3 Thermostat issues Just to close this out - purchased a LS1 thermostat housing with a 160 degreee stat Part # is LPE-L310045297 Bolts in - will fill with fluid tomorrow - If I don't update again All is good !! __________________ 1972 K5 Build - plans - LS3-6L80e-One Tons..... 1971 CREWMAX Build.....at body shop for couple more years

05-11-2023, 04:56 PM	#7
LS short box Registered User Join Date: Jun 2015 Location: Carlos MN Posts: 1,923	Re: LS3 Thermostat issues Just a tip that has worked for me. Before you install the new stat I drill three 1/8" holes in the metal flange that hold the gasket. Seems to help getting first start air pockets out of the system.

05-12-2023, 08:15 PM	#8
87chevy.com BMW & ASE Master Certified Join Date: Feb 2004 Location: Houston, Texas Posts: 1,255	Re: LS3 Thermostat issues the thermostat you pictured is from 2 different pumps. theirs 3 different length thermostats, LS thermostat is not universal... its specific to the pump. good video: https://www.youtube.com/watch?v=2apgFAuo4Dk __________________ 1987 Silverado - L83 5.3 w/ 6L80e ,A/C,P/W,P/L,TILT, HID projectors, Wilwood C-10 Pro Spindles w/ 2018 silverado front brakes & C-5 Corvette Rear Disc Brakes 1999 BMW 528i - 5.7 LS1 w/ 4l60e, Ford 8.8 IRS w31 spline posi & FX-r projector retrofit New project: 2006 BMW x5 6cyl AWD to L83 6l80e 4wd to 2WD / RWD A poor man buy's it twice finally got my domain name back, 87chevy.com.... site rework in progress



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