I can't say I've much experience beyond the 491 (in terms of 'big' ng engines), however from what D&S and C&TS guys who have visited in the past have said, in addition to testimony from one of her former Rio Grande firemen, she steams better than most. I can definitively say that she's a peach of an engine though- a free steamer and smooth runner with more pull than the museum could ever really need.
On the note of 491 being a later version of 1126, I think that's a bit of an over simplification. 491's first boiler course, steam dome, and some cab fixtures are from 1126. Her tender is also from a C-41, though from what we can tell is likely 1125's. The frame, running gear, remaining bits of boiler, cab, steam chests, cylinders, wheels/axles, and just about every other bit on her was made/purchased specifically for her life as a K-37. There's certainly more new build in her than old, and is a bit further from "A C-41 put on NG wheels" than most realize. Personally, I've always heard that the frame of an engine marks its identity, and a boiler is secondary to that. Some may see it the other way around, but seeing how little of the boiler is still from 1126, I doubt it'd be the linchpin here.
Cheers!
- Brett W.
Edited 1 time(s). Last edit at 08/19/2018 07:34PM by Brett Wiebold.