Hi, someone can suggest me a good cpu aircooler for this cpu: I9 7940x (not overclocked) and compatible with x299 dark.
My previous cooler NH D15-S ( used with asrock x99) ( in noctua website is listed as mechanicaly not compatible).
i'm using now an AIO but if it'll wail i come back with an air cooler. 
Walter

I'm using the BeQuit Dark Rock 4 until the watercooled setup is complete.
 
This cooler is capable of 4900 Mhz on all cores(9800X) using OC robot. Mind you, this is a 100C celcius plus gig at full load :)  So do not use 24/7 :(
 
I am using this setup at stock speeds until all the parts are in to watercool it.
It is however a verry snug fit, there is a paper thin gap between cooler and vrm fans, see photo.
 
 PS
On stock speed it runs at +/_ 40 C, the photo is taken at 4900Mhz