Les & Kevin: Actually I think the D&RGW was cheap on valve lead. The mechanical specs show only 1/8" of lead on all the K's. It doesn't take much wear on the valve gear to get 1/8" of lost motion, whereupon the valve goes blind on the lead. Jack Campbell and I talked about this when he set up 463. He opened up the lead to 3/16" and the engine ran very well. The 489 always ran better the others hooked up high. I always suspected the Salida shop boys opened her lead up a bit, but never got to look inside her valves to prove that.
The deal with the engines running hooked high is caused buy the big swing the eccentric crank has. Look at a video where you can see the valve gear and notice how big and arc the link swings and notice the angle the eccentric rod goes thru in the process. At forward center the crank is at the top, the eccentric rod angles downward at a rather steep angle. When the engines were designed, they got as much throw on the link as possible without getting things in a bind. The greater the throw on the link, the greater the travel on the radius rod and the greater the movement on the valve. Therefore, you can hook the reverse lever up much higher and still have enough valve travel.
....clear as mud, right?