 Engines needed to be overhauled about every 20 hours.The reliability of Gnome engines license-built by The British Gnome and Le Rhone Engine Co. gave an overhaul life of about 80 hours mainly as a result using a special tool to roll the 'L' section obturator rings.The problem of thermal distortion was effectively cured on the Bentley BR1 engine by using aluminium cyclinders, for good thermal conductivity, with cast iron liners shrunk in.