From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Performance graph comparing a Standard U Series 25 HP engine with various cylinder head, carburettor, and camshaft configurations.
| Identifier | ExFiles\Box 55\1\ Scan160 | |
| Date | 5th July 1932 guessed | |
| COMPARISON OF STANDARD U SERIES 25 HP CHINA 20 G IV AND IGG & JI HEAD R.R. CARBS TO LEC 2324 RM{William Robotham - Chief Engineer} 65 ① JI HEAD 6.2 C/R 110°S CAMSHAFT CARBS TO LEC 2324 .9" CHOKES AIR SILENCER FITTED. ② CHINA HEAD 5.6 C/R 110°S CAMSHAFT STP CARB 15% LARGER CHOKES. ALL TESTS OPEN EXHAUST ① AIR INTAKE SILENCER REMOVED. B.H.P. B.M.E.P R.P.M. T.D.C. EX IN 3º 3º 46º4 O2D GAGE CAMSHAFT E/57177 | ||