Hot Water posted:No, those 567C engines were up-graded with 645 roots-blown power assemblies, still within the "C" crankcase. The "D" engine designation was the turbocharged versions of the 567, such as the 16-567D3 in the GP30 model, and the 16-567D3A in the GP35/SD35/DD35 models. Thus, what you heard was a louder exhaust sound from those 645 power assemblies and no exhaust silencer.
Not to split hairs, but the "D" engine came in domestic models GP18, SD18, and GP28 from the factory (and in some export models).
The engine model according to the LOM is 567D1, or if you prefer, 16-567D1.
Here is the manual link:
http://www.rr-fallenflags.org/manual/manual.html
Go down to the GP18.
The "D" engine brought in the fabricated water jacket on the cylinder liner, which replaced the cast jacket cylinder liners in a "C" engine. BIG improvement, as the cylinder liner wall thickness was much easier to control on the fabricated jacket cylinder liner.
Regards,
Jerry
