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).
Tappet clearances and weights for different exhaust valve types.
| Identifier | ExFiles\Box 35\3\ scan 046 | |
| Date | 15th August 1923 | |
| R.R. 403A (40 H) (SL 42 12-7-23). J.H.D. EXPERIMENTAL REPORT. Expl. No. 2764 REF: Hs{Lord Ernest Hives - Chair}1/LG15.8.23. best shape, and we should gradually weed the others out. Tappet clearances necessary to ensure exhaust valves seating. Type of Valve. | Tappet clearance at normal temperature. | Tappet clearance when engine cold. | Weight of Valve. --- | --- | --- | --- Pre-war 45° | .002" | .001" | 6 ozs. 6 drams. Pre-war 30° | .006" | .005" | 6 ozs. 6 drams. Present std. | .009" | .008" | 6 ozs. Present std. 45° seat. | .006" | .005" | 6 ozs. Present std. flat head 45° seat. | .0015" | .001" | 7 1/2 ozs. | ||