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. These changes, referred to as 'Modified Front End', were such an improvement that the rest of the A2 and C classes were progressively modified, as well as all of the K, N, S and X classes.