Re: What were the reasons for the K-27 valve gear differences?

1) Search the archives, this has been extensively discussed in past.
2) Buy the excellent book _The Mudhens_ which came out a couple of years ago.

Short answer: Vauclain Compounding was particularly ill-suited to helper type operations, on top of all the other problems that turned up with it in general. By 1912 D&RG had converted almost all the class 125 engines to simple with slide valves & Stephenson valve gear. In the early 20's it was decided to further change them to superheat & piston valves. This program was slowed and then stopped after the arrival of of the K-36 & K-37's, not to mention the Depression. At the time conversions stopped 450, 451, 457 & 460 had not yet been changed. 462 had received piston valves but not yet been supe heated (never was).

Outboard/inboard admission was a subject of debate in RR circles of the time as to which was better, D&RGW went 1st one way then the other. Main practical difference seems to have been in snow plowing.

At 1st D&RGW tried to retain Stephenson gear on converted engines and this is why some of the engines have valve chest at different angle on cylinders. In the end gave up on this and all super heated engines (and 462) received Walschaerts(sp?) gear. Or at least it has been stated thusly previously on this forum.

All of the above from memory and probably full of errors, check the archives for the correct info.

hank