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).
Investigation into engine misfires, spark plug gaps, and carburettor problems.
| Identifier | ExFiles\Box 82\5\ scan0107 | |
| Date | 9th May 1937 | |
| HOTEL DE FRANCE, CHATEAUROUX. Indre. France. 9th May 1937. Rm{William Robotham - Chief Engineer}/GWH{George W. Hancock - Head Chateauroux}/AJG/4/JAB. To. Rm.{William Robotham - Chief Engineer} c.c. Rm{William Robotham - Chief Engineer}/GWH.{George W. Hancock - Head Chateauroux} 3. B. IV. We have been experiencing very bad misfires on pick-up and occasionally at high speeds. We found that the sparks were jumping from the leads where they come out of the wiring tubes and also at the plug terminals across to the manifold flanges. On investigation the leads were all very badly cracked, and we have replaced these with new ones. The old ones have done 8,123 miles in France. This did not cure the sparking at the plug terminals, and we noticed it was worse with a weak mixture. We examined the plugs and found the gaps were as follows :- (1) .036 (2) .038 (3) .038 (4) .042 (5) .043 (6) .043 These were reset to .018 and there is now no trace of misfire. The plugs are the K.L.G. type FLB.30.X which on the 27th April were re-set from .028 to .020 after 8,000 miles, since when they have covered a further 1,400 miles, and except for burning of the points look quite good. We noticed that the sparks jumped outside most frequently across Nos. 4,5, and 6, this is understandable with wider plug gaps. We found that the rear carburetter was not coming in until about 1000 r.p.m. which incidentally coincided with cessation of sparking at the plug terminals. Also the guide pin for the piston was loose and probably caused jamming. This is no doubt the cause of the wider plug gaps of Nos. 4,5, and 6. The carburetters have been re-set and the slow running and pick-up are very good. ---------------- Rm{William Robotham - Chief Engineer}/GWH{George W. Hancock - Head Chateauroux}/AJG. AJGardiner * The plugs are FLB 50 X were reset after 2,300 miles not 8000 on April 27 as stated * have covered a further 7,100 miles not 1400 Frank. Waller. | ||