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 adjustments and requirements for different types of spark plugs.
| Identifier | ExFiles\Box 162\6\ img173 | |
| Date | 22th August 1932 | |
| Ref HS{Lord Ernest Hives - Chair}/RW/AJ. "ONE OF THE L.M.S. HOTELS" Dornoch Hotel, Sutherland. 22.8.32 Dear Mr. Robotham Your letter of the 18th inst. has been sent on to me for attention. I am glad to hear that the HII 14-3 14 m/m 3 point car plug is so far satisfactory, but that you would prefer another 0.1" on the reach. This we can easily do but I will understand that an increase in the reach will slightly reduce the pre-ignition limit. As soon as I receive the sample K.L.G. plug you are sending I will give the necessary instructions to our works to make up 1 dozen plugs to the new reach & length of barrel & have them forwarded to you as soon as possible. I also note that for Super Charged car work you find the A15 satisfactory, but that you would also like the reach of this plug increased by 0.1". This again will reduce the pre-ignition limit somewhat, but we will make up a dozen samples for you to try. Before doing so would you please let me know what length of barrel you require for this model. The A15 has a 13/16" barrel, & if we can shorten has a 16 | ||