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).
Timing and camshaft modifications on the Phantom II and 25 HP models, detailing power curve increases.
| Identifier | ExFiles\Box 13\2\ 02-page108 | |
| Date | 22th June 1931 | |
| 87090. To E.{Mr Elliott - Chief Engineer} From Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}6/KT.22.6.31. TIMING AND CAMSHAFTS ON P.II. Herewith power and M.E.P. curves for the 114º camshaft on the P.II. We find that with a 112º camshaft on the 25 HP. we get an increase of anything from 3 - 5 lbs M.E.P. over the whole range with twin carburetters, by altering the rocker centres so that we increase the valve lift by .050". This does not make our rocker ratio very much different from the P.II. and expect will give us some power at top speeds with low depression carburetters. The increase in lift does not seem to put us in any difficulty with valve bounce or noise. We will let you have further figures when available. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||