Cary S-2's

[doctorwayne]

If I'm not mistaken, the early Alcos had air-cooled turbochargers, which were prone to problems. Later models used a water-cooled version, which was also available as a retrofit for older locos. I believe that change also resulted in a change in the exhaust stack.
I'll contact someone who may be able to shed more light on this subject.

Wayne