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).
Misfires, spark plug gaps, and tyre wear on a Bentley 8.B.V. vehicle.
| Identifier | ExFiles\Box 97\5\ scan0126 | |
| Date | 18th March 1939 | |
| 400b To. Rm{William Robotham - Chief Engineer} (Rm{William Robotham - Chief Engineer} is struck through) c. Rm{William Robotham - Chief Engineer}/Gry{Shadwell Grylls} (Rm{William Robotham - Chief Engineer} is struck through) c. Rm{William Robotham - Chief Engineer}/FJH.{Fred J. Hardy - Chief Dev. Engineer} (Rm{William Robotham - Chief Engineer} is struck through) CHATEAUROUX. L/.18.3.39. FJH{Fred J. Hardy - Chief Dev. Engineer} (signature) 8.B.V. - BENTLEY. Thank you for the various memos received. We are at present trying to obtain a figure for effect of oil level in front dampers as requested. Regarding misfires on pick-up, the only report of these during the present test was by Whyman on 31.12.38, 2.1.39. The plugs were re-set from .030" to .020" by myself on 7.1.39 which cured the misfires. The next report was your own on the run to Val d'Isère. The plugs were again re-set from .030" to .020" and no further misfires have occurred. When they next occur, we will change over to the Delco ( for which we have all the necessary bits ) and see if it makes any difference. Our experience with Bentleys in the past has been that when the plug points have burnt from an initial setting of .020" to anything over .030", they require re-setting to ensure freedom from misfires. At the same time we believe that new plugs set at .030" will not misfire in Bentley engines, which probably explains why you do not consider .030" to be excessively wide. With the Bentley C.R. and more particularly with the higher 7 to 1 ratio now being used, we recommend .020" plug gaps. Replying to Gry{Shadwell Grylls}'s query re the special Dunlop 4 ply tyres, two of these have been returned to Derby with burst walls, two are in use on the car, and two are in the garage in a partially worn state, but good for further use. all these we will return to you when they are worn out. We have examined the standard India and Dunlop 90 tyres run during the last 15,000 miles test on 8.B.V. and find that every front tyre shows signs of eccentric wear. You will note from the Daily Reports that the specially balanced Avons have not been subject to this trouble, and therefore, recommend that balance weights of some kind be used for production. We will again balance the next new front tyres fitted to confirm this. We have not yet received any more Avon tyres. We note that all the front tyres wear considerably more on the inside than the outside of the tread. We suggest that with the new reduced out of centre point yokes and pivots which are to be tried, a certain amount of dish on the wheels | ||