[2] It had been necessary for Victorian Railways to strengthen bridges at Dudley Street, North Melbourne and along the lines to Woodend and Seymour on which the new locomotive was expected to run.

[5] By 1924 C class locomotives were operating on the Bendigo, North Eastern, and Wonthaggi railway lines, where full trainloads of bulk goods were available.

Key shortcomings included a very long, 9 feet 7 inches (2.92 m) manually stoked firebox that was difficult to fire and prone to clinkering, and an undersized boiler.

In an attempt to rectify these problems, locomotive C 5 was fitted in 1933 with a new front end, based on the Association of American Railroads (AAR) design of self-cleaning smokebox, to improve steaming qualities.

The results were very promising and led to further experimental work, using A2 class locomotive A2 998 as a test bed and conducted under the direction of VR Rolling Stock branch engineer Edgar Brownbill, in streamlining the steam passages and other changes to reduce back pressure on the exhaust side and increase efficiency.

Despite the success of the conversion, C class locomotives were still prone to running out of steam when pushed on long rising gradients.

Unlike the later conversion of X class locomotive X 32 to PBC firing in 1949, this early experiment was not considered a success and C 16 was returned to black coal operation.