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).
Conclusions from tests comparing Delco and R.R. ignition systems to resolve engine misfiring issues.
| Identifier | ExFiles\Box 162\2\ img013 | |
| Date | 27th March 1939 | |
| Mx.{John H Maddocks - Chief Proving Officer}1/MG.27.3.39 (continued) - 4 - to overcome misfiring with R.R.distributor, by using a rotor air gap of .024. Tests made to determine whether this dimension is critical indicate that the gap can be varied ± .005 without causing irregular running. The conclusions arrived at from the foregoing tests are: (1) The Delco ignition has a greater margin of immunity from misfiring using .030 sparking plug gaps with oxidised electrodes, and the indications are that this is due to the make/break ratio of 70-30. (2) The R.R.ignition will function with a spark plug gap of .030, using a .024 rotor air gap. The margin of safety on R.R.ignition could be increased by using a smaller plug gap. We do not want to do this unless forced to it, as we must accept that large sparking plug gaps conduce to good idling and pulling at low speeds, although on this particular car no deterioration in these qualities has occurred when using plug gaps of .020. | ||