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 knocking caused by tight pistons and pre-ignition from incorrect sparking plugs.
| Identifier | ExFiles\Box 180\M3\M3.7\ img013 | |
| Date | 12th August 1919 | |
| Contd. -2- EH1/LG12.8.19. ----------- The only complaint we have, is that if we go very fast on top gear, the engine commences to knock. The noise of the knocking is exactly similar to what we get with a tight piston and we think that in this case it is most probably due to a piston getting tight but not tight enough to seize. The reason it was worse with the bad sparking plugs was because the pre-ignition causes over-heating. The plugs you were running in 7-CA were of a type which we have condemned because there was a tendency for pre-ignition. The K.L.G. plugs which are being used on be standard cars are much better in this respect. EH. | ||