The arduous Calder Valley route meant they needed more power than most sets, so they were fitted with Rolls-Royce C6NFLH engines, and when delivered they had the highest hp/ton of any of the DMUs, including the lightweights. With a set weighing 87½ tons (tare), this gave a power-to-weight ratio of 8.3 hp / ton, which was appreciably higher than any other all-diesel sets in use at the time using normally aspirated engines. Performance tests included a standing start against a ruling gradient of 1 in 261 and a set in tare condition achieved a speed of in 45 seconds, in 2 minutes 4 seconds, and in 4 minutes 6 seconds. From a standing start on a 1 in 45 gradient a speed of in third gear was reached in 42 seconds. Each set had 24 first class and 159 second class seats.