New Cooling System what to use?

[Scoobum]

Are you sure the headgaskets are intact?

[ULYCYC]

As said sounds like a headgasket.  I thought all was good before the radiator and cooling system work. That's why I said check thermostat

[Scoobum]

Dave, if you have to pull the engine, let me know.

[Just a Six?]

Thanks guys I'll maybe check compression again but all was good & now something weird is going on because after 1-2 mins run time it's puffing oil as well? I never really drove the car much at all this year so it just makes no sense?    

[Scoobum]

If you need help wrenching on it, I'm a phone call away.

[Just a Six?]

Thanks Brad lets see how it plays out but I may take you up on that offer! 

[Scoobum]

Check the DP for oil. Maybe the turbo is leaking. When the DP gets warm it'll start burning off.

[nocooler]

Did you fill the coolant system with the nose up in air so the fill point is the highest point? If all you did was change cooling components, I’d say you don’t have all the air out of the system. I don’t remember Buick’s being a problem but some of the newer stuff it can be a pain the bleed all the air out.

[Scoobum]

Jeremy might be correct. I had a helluva time getting the air out of mine. Throw a pan under the rad and let it burp itself.

[nocooler]

https://smile.amazon.com/OEMTOOLS-87009-No-Spill-Coolant-Filling/dp/B01A2CQSU6?sa-no-redirect=1

These are worth every penny. I used mine for the first time changing the coolant on the wifes Honda.  

[Just a Six?]

There no thermostat in it now & it has coolant flowing strong plus I pre filled the heater core so I don't think it's air but nothing else makes sense for the changes I made? I did an oil change Friday & it was on the darker side but no milkshake or particles of any kind.
I've been chasing both issues for weeks checking everything twice? 
Yesterday pistons #3 was 150 & #5 was 160 after 30 secs run time but Tuesday I'll check compression again on all of them.
Brad I didn't check the turbo but the wheel on intake side was pretty solid the beginning of the year although I haven't checked the exhaust side in a few years so it's time to pull off the downpipe. I know this car pretty good & I'm chasing a ghost with both my issues?
I used to pull the motor every fall just for fun but it's not as appealing anymore. 

[Just a Six?]

https://smile.amazon.com/OEMTOOLS-87009-No-Spill-Coolant-Filling/dp/B01A2CQSU6?sa-no-redirect=1

These are worth every penny. I used mine for the first time changing the coolant on the wifes Honda.  

That looks like a handy tool to have for only $20

[ULYCYC]

Drill a 1/32 hole in the thermostat. It takes care of all the air bleeding issues.

[Steve Wood]

and yes, you need a thermostat for proper cooling.

Maybe you can find an exhaust gas kit tester to check the coolant for signs of exhaust indicating a blown hg

[Scoobum]

Some of the ARP studs don't sit correctly and need extra washers for proper clamping force. Not sure if that applies to your setup.