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).
Engine valve clearances, feeler gauges, and camshaft design, including proposals for the Phantom model.
| Identifier | WestWitteringFiles\S\2April1928-June1928\ Scan074 | |
| Date | 7th May 1928 guessed | |
| (2) The push rods and expansion of the blocks is assumed to keep the clearance normal. The only difference would be in the exhaust valve taking up, so that the exhaust valves should be set with more clearance. Should we be correct in saying the inlets should be .005 and the exhausts .008" cold? Regarding the feeler gauges the .002 should be abolished altogether and replaced by .006 or something more useful. The .030 should likewise go as we should not set plugs to this since we are increasing the compression ratio. Regarding the cam lengths I am proposing that we make two forms to suit our rollerless tappets, 53 and 57 divisions long over the heavy accelerations, which are respectively one division longer than the inlet and exhaust we are at present using on the Phantom. Camshafts can be made up for experiment with different angles between cams: diagrams seem best at 110°. We are convinced that it is a mistake to endeavour to use the same cam for both inlet and exhaust, resulting in noise or some loss due to the inlet opening too early. R.{Sir Henry Royce} | ||