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).
Letter discussing spark plug issues related to deposit formation from cold induction and potential remedies.
| Identifier | ExFiles\Box 162\4\ img207 | |
| Date | 27th November 1936 | |
| To W.A.Robotham Esq.(Messrs. Rolls-Royce Ltd.) 2. DATE 27-11-36 amount of moisture issuing from the exhaust pipe, rather more than one usually sees in the general run of cars when starting and idling. Whilst I have not seen an actual section of your cylinder head, I should also judge that the plug is very well cooled, which is naturally an advantage, but since it is located fairly near to the inlet valve it probably gets the benefit of the first inrush of wet mixture when starting. All these points, of course, may not be of very much help to you, but it does confirm our theory that the initial deposit formation on the plugs is caused by cold induction conditions where a considerable amount of liquid fuel is involved, and it is possible that a considerably warmer running plug, to avoid the initial build-up of deposit, could be used without running into pre-ignition trouble when the car is really pushed. I do not know whether you tried, in the early days of the Bentley, different spark plug positions relative to the valves, but if you happen to have a cylinder head with a spark plug location nearer to the exhaust valve it might be a good idea to try it out in a test car to see whether the plug keeps drier during the starting and warming up periods, and if the deposit collects less rapidly. It may be that the older K.L.G. plugs will give better average results than the new ones because they probably run somewhat warmer. I have brought over a set of K.L.G.850 plugs which are defective and which we tried out in Slater's car, and I am trying to have them tested in every possible way to see whether we can get down to the exact nature of the trouble. Although I am not very hopeful that we will find anything in this direction but must look for it along the lines previously suggested. Since seeing you I have had one of the people in this office asking the other manufacturers whether similar trouble has occurred, and so far we have absolutely no evidence of it. If you would like me to come to Derby at any time to discuss this matter further with you I hope you will not fail to advise me. With kind regards, Yours sincerely, FRBanks. FRB/BB | ||