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).
Page detailing compression ratios, tappet clearances, and power correction.
| Identifier | ExFiles\Box 69\4\ scan0277 | |
| Date | 1st February 1925 | |
| R.R. 493A (50H) (D.B. 175 25-9-24) J.H.D. EXPERIMENTAL REPORT. -4- Expl. No. REF: Hs{Lord Ernest Hives - Chair}/ACL/LG6.2.25. poured into the cylinder - noting the amount put in - until it is level with the bottom threads in the plug holes. To ensure that there is no air lock, one of the valves should be very slightly opened to permit any air that may be present to escape. The capacity of the combustion space should be 25 to 26 cu.ins. and this gives a compression ratio of 4.12 to 4.0 to 1. The compression ratio is given by the formula :- R = 78.02 / V + 1 where V is cu.ins. TAPPET CLEARANCE. For normal running, the tappets should be set to have .003" clearance when the engine is cold. The clearance will increase until normal temperature is reached, light running. and the exhaust valve clearance will decrease again as the speed and load increase. For test bench work, we strongly advise a larger tappet clearance than normal temperature is reached, because a lot of the work is done at full loads and for longer periods than will occur on the road. Therefore, set the valves at .006" clearance when the engine is cold. POWER CORRECTION FOR TEMP. AND PRESSURE. We should not advise any different practice with regard to power correction than has been employed in the case of the 40/50 HP. contd :- | ||