WEBER TURKEY - Open or closed lid openings?
Bottom vents are the most effective at feeding oxygen to the coals. Top vents are the most effective at letting out smoke and fumes. If you close either one, then there won't be good airflow through the kettle.
Generally I'd say leave the top one wide open, and only close the bottom one partially if the grill is running too hot.
In general, I don't close either one until my grilling is done and I want to kill the coals, at which point I close both.
"The poster indicated the best results are from leaving the top vent open, and slightly closing the bottom if you want to slow down a too-hot kettle."
This is the truth.
In practice, I think I have never had to close the bottom vents even a little.
Now why can't I find some verification of this from Weber sources?
As someone replied to me in an old BBQ thread, partially closing the top vents will sometimes cause ash to settle on the food, with a nasty gritty texture. I find this to be true.
The poster indicated the best results are from leaving the top vent open, and slightly closing the bottom if you want to slow down a too-hot kettle.
But be careful. Our old Weber had manual vents on the bottom. We finally replaced it with the kettle with the ash-catcher on the bottom, so you have to regulate the bottom vent with a sliding lever. Impossible to see just how "open" the bottom vent is. I killed the coals for our pre-holiday turkey last week and had to start an emergency chimney of coals to add. What a pain. The lever was not at "closed" position, but the vent WAS. d-oh!