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).
Technical discussion on achieving increased valve lift for the 25HP 'CHINA' engine by altering rocker ratios and cams.
| Identifier | ExFiles\Box 102\5\ scan0069 | |
| Date | 12th September 1931 | |
| HS.{Lord Ernest Hives - Chair} BY.{R.W. Bailey - Chief Engineer} } FROM R & E.{Mr Elliott - Chief Engineer} X 5090 R1/112.9.31. C. to SG.{Arthur F. Sidgreaves - MD} WOR.{Arthur Wormald - General Works Manager} RG.{Mr Rowledge} 25HP. 'CHINA' & INCREASED VALVE LIFT. We do not agree to shifting the centre of the rocker so much as to make the ratio 1.34 instead of 1.2, (1.22 corrected for rocker curvature) for obvious reasons, especially for tappet clearance. You ask for .050" increased lift. The best way to get this is by altering the centre of the rockers .025, i.e. 1.255 ratio (corrected) and increasing the lift of the cam .030, which gives lift of .314". This would be our best compromise, and will go into the present material. New cam forms will probably be needed. The length between heavy acceleration .013 clearance is: EX: 61 DIV: --- IN: 57 DIV: The heavy acceleration of the 57 div: inlet cam - Schd 1153. - equals .003. We now use .004 (at least) to .0045 for car work. Phantom 2. equals .0049 - see Le c 2918. All this suggests that P.2. standard valve timing is quite good, so that the low power has never been due to that cause. R.{Sir Henry Royce} | ||