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).
Pre-ignition issues with Bentley sparking plugs caused by mica flaking.
| Identifier | ExFiles\Box 162\4\ img114 | |
| Date | 23th August 1935 | |
| K/KC. From Hs{Lord Ernest Hives - Chair}/Wst. c. to Hd{Mr Hayward/Mr Huddy}/SB.{Mr Bull/Mr Bannister} 86001h Hs{Lord Ernest Hives - Chair}/Wst.7/MA.23.8.35. BENTLEY SPARKING PLUGS. We have now been able to arrive at a definite conclusion confirmed by Messrs.K.L.G. that the trouble with your plugs is pre-ignition, the pre-ignition being caused by the mica flaking and remaining incandescent. Cleaning the plug cures the trouble but after a short time it is again apparent. It appears that the mica wrapping on some plugs is more subject to this sort of thing than others. We have always been suspicious of rolled mica plugs for high duty work hence the development of the 850 plug which is of mica washer construction. Hs{Lord Ernest Hives - Chair}/Wst. | ||