I ran those number years ago and figured k27's had more grate area to cylinder size than a 480 bit a bit less than a 490. The great area of a K27 is the same as a K28, but the K27 has smaller cylinders.
The problem with K27's is the firebox is very shallow with little room up front between the grates and the arch. You had to be a good shot with the scoop. Too high and you'd hit the arch and the coal would fall in the middle. Too low and the coal would land short of the front. Either way, you end up with a pile about 2 feet from the front - a pile that would extend from the grates all the way to the arch - with nothing burning against the flue sheet. The shallow box didn't allow much room for air to combine with the gases, which effected its ability to steam and keep the smoke down.
It took lots of little scoops of coal to keep 463 against the peg. Her hard draft would burn the scoal right off the scoop. You had to keep after her, and be on your feet most of the time (right next that unlagged backhead). She had real big injectors (10's) which were oversized for her. They wouldn't cut back far enough to run all the time and you had to trade water and steam - fire the gun off when you had 199.95 lbs, then fire until you dropped to 192 or so, kill the gun, get your steam back, start the gun, etc. You were a real busy fireman. Even at its best by the time you got to below Coxo the fire was getting deep, and her steaming ability was beginning to fade (along with the fireman). If a stop at Cresco was made, it gave the fireman a chance to shake the fire down a bit, which amde life on the upper part of the hill much easier. After a few days on 463, firing 489 was like laying off.
