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).
Investigating the causes of engine misfires in 25/30HP and Bentley cars.
| Identifier | ExFiles\Box 150\1\ scan0277 | |
| Date | 19th January 1937 | |
| 15.1.37. To Rm. {William Robotham - Chief Engineer} 1282 Typed - 19.1.37. RE. MISFIRES ON 25/30HP. and BENTLEY CARS. I paid a visit yesterday to our Kingsbury Depot to find out their real troubles with misfiring. I gathered from my talks with Mr.Clark that whilst they were having a certain amount of trouble due to dirty plugs, it had not by any means reached an epidemic stage, and throughout the last quarter there had been only 16 complaints. These consisted of 8 - 4¼ Litre cars and 8 - 3½ Litre cars, in 6 cases the plugs were changed, and in 10 cases the plugs were cleaned. There was evidence of course that in most cases the plugs were leaded up and that the mileage at which the plugs started to misfire varied from 291 miles to 22,000 miles. With the exception of an isolated case however, no car has been returned to Kingsbury for misfires after it has once received their attention. The testers down there are of the opinion that the main cause of the trouble is the mis-use of the mixture control, i.e. running the engine from cold too long in the strong position. The information I gathered from talks with our Repair Department people at Derby was somewhat similar and whilst they have a little plug trouble, it has not by any means reached serious proportions. There is an under current of feeling that lead fuel is partly responsible for some of the misfires, but no concrete evidence can be obtained, in fact customers running on straight petrol have had plug trouble, one in particular changed to straight petrol with new plugs and was soon back again with mis-firing. The 4¼ litre model does not appear to be any worse than the 3½ litre in this respect, but it is worse for detonations, last quarter there were 17 complaints. 13-4¼s. and 4-3½s. In the case of the 4¼ models, 4 were cured by modifying the cyl. heads, 8 by adjusting the ignition and 1 by an R.10. decarb. after 5100 miles. I handed to Mr.Clark 3 sets of LB.9. Champion plugs and one set of LB.8. Champion plugs and asked him to fit a set into the first car that came in with a complaint of misfiring and to report on them direct to Rm. {William Robotham - Chief Engineer} continued. | ||