Someone I know, on witnessing a Yak start-up from outside described it as 'biblical' - lots of noise, lots of smoke, the earth shaking, and the smiting of lesser objects. From inside, it's a 3-handed work of art to coax that big 360 Vendeneyev radial into life, and get it to become self-sustaining.
Once it's running, it sounds just glorious - a syncopated combination of many rhythms. The nine pistons thrashing up and down in that strange order only radial engines have; the prop-drive reduction gears rumbling; that massive 11 foot paddle prop beating the air at about half engine speed; the supercharger's muted but high-pitched whistle as it spins at a phenomenal rate; the un-silenced drainpipe-sized exhaust outlets. On top of this there is the cam ring, valve gear, magnetos, generator, various pumps, the prop governor, air compressor, and several other ancillaries all adding to the beautiful cacophony.
Love it!!
SSD