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 to The Rover Company Ltd. discussing engine valve grinding, decarbonisation, and fuel performance.
| Identifier | ExFiles\Box 127\3\ scan0192 | |
| Date | 1st September 1937 | |
| 109? (crossed out) (091) Rm{William Robotham - Chief Engineer}13/R.{Sir Henry Royce} 1st Sept., 1937. G.F. Searle, Esq., The Rover Company Ltd., Oliver Street, C O V E N T R Y. Dear Mr. Searle, Replying to your letter of August 30th, it is now sometime since we gave up grinding in valves a second time after our engines had been run. Of course, for many years this was an 'Old Spanish Custom', and at one time our valve steels were so poor, and our testing so thorough, that having very nearly worn the engine out before we delivered it to the customer, we found it necessary to re-grind the valves. To-day we consider this an absolute waste of time, because all we do is to put a seat on the valve when it is cold, and there is no guarantee that it will sit on this seat when it is hot. In our Bentley Instruction Book, this being the car which is naturally most sensitive to pinking due to carbon, we do not make any recommendations as to a specific mileage at which it is desirable to have the car decarbonised. In spite, however, of this being a high performance engine, we say that if run on Ethyl it should not be necessary to remove the head in less than 10,000 miles. If, however, the owner persists in running on some fuel with a lower octane value, then he may expect to have to remove carbon at 6 or 7,000 miles. Personally, I have come across several customers who have done 12,000 miles, or more, and I always recommend them to go on running the car without disturbing anything until it shows signs of losing efficiency. I do not quite understand the detonation characteristics of the Rover, because it has a small cylinder without a very high compression ratio, and yet, after 2 or 3,000 miles it is practically impossible to run it on anything except Ethyl, and my particular car, when it came back to the factory, could be made to pink on Ethyl. Now, of course, after 2,000 miles' running, it is appreciably worse. Yours sincerely, | ||