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).
Engine misfiring issues related to petrol quality and spark plug gaps, and a growling noise from the rear axle.
| Identifier | ExFiles\Box 101\1\ scan0268 | |
| Date | 10th May 1936 guessed | |
| -3- This is with Shell petrol, which detonates very badly, no other petrol obtainable here. We can quite believe that in another month's time this test would be quite different, but the gradient is not sufficient to cause overheating with the present cool atmosphere. We have however found that in top gear while on the gradient the coil ignition breaks down below 25 m.p.h. misfiring started. We tried various settings of the plug gaps and until we closed them to .016" there was still misfiring. Taking a set of new plugs we again had to come to .016" to cure the misfire. With the plugs sets to .016" gap there was hardly any sign of the hesitation that we have been experiencing. When the misfiring occurs we can hear the spark jumping in the distribution. It is the same on the Bentley. We tried separating the ignition wires etc. but to no avail. We thought at first that the current was tracking through the insulation of the distributor rotor, but by placing a piece of paper under the distributing finger we proved that this was not the case. It sounds like - and as far as we have been able to prove, is - jumping from the finger to the metal case inside the distributor. It is exactly the same on the Bentley. Rear Axle. The rear axle during these tests has developed a real growl on torque approx. 25 m.p.h. It has developed to such an extent that we gave up climbing. It is not on the over-run. We shall run the car back to Chateauroux and it depends on what it sounds like, whether we shall proceed to Paris and have the axle examined. There has been no loss of oil. | ||