LS3 Thermostat issues

[6600DURAMAX]

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]

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]

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]

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]

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]

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]

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]

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