I’ve never devoted much thought to trapped air in my cooling system. I assumed drilling the t stat took care of any concerns there.
My 235 likes to puke until it’s slightly below the top row of radiator tubes. And I do have a recovery tank with an outlet.
Is that a sign of trapped air in my system?
It is more of a sign that the recovery system isn't working right. Is the radiator cap designed to recover coolant? The way to tell is that it will have a spring loaded "plunger" with a rubber gasket AND another rubber gasket on the underside of the top of the cap. If that gasket isn't there the radiator won't pull liquid back in from the recovery tank as the radiator cools off. Leaks in the recovery system can also cause air to be pulled back into the system.
A good system will purge the air in the engine after a few cycles of running and cooling off. It will leave the top tank of the radiator full of coolant after the engine cools off.
You might try parking the truck on a steep uphill grade and running the engine thru a few heat up/cool down cycles. That should get any air trapped in the engine into the radiator upper tank where the coolant recovery system can eliminate it.
My truck is a GMC. It has a pipe plug in the head above #6 cylinder that are used in some models to mount the temp sensor. I don't know if the Chevy 6 cylinder engines have a similar plug. When refilling the cooling system, I park the truck on a steep incline with the back end high (make the rear of the engine the highest point in the engine) and loosen the plug above #6. When it quits bubbling (all air out of the block) I tighten the plug.
