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).
Noisy tappets and clearance changes for a 35-EX Phantom III engine.
| Identifier | ExFiles\Box 92\3\ scan0309 | |
| Date | 8th June 1937 | |
| To Rm.{William Robotham - Chief Engineer} from Rm{William Robotham - Chief Engineer}/IMW.{Ivan M. Waller - Head of Chateauroux} 300a Typed 8.6.37 35-EX.Phantom III. Tappets without hydraulic adjustment. 1. NOISE There were complaints of noisy tappets when the car was received from the Shop for 15,000 miles test. The clearances specified were inlet .006" and exhaust .008" with the engine hot. It was found that owing to irregular base circles on the cams, variation in tappet clearance of .004" occurred, and the noise complained of was attributed to this. It was found that setting the tappets at .004" and .006" gave an improvement in noise, and it was agreed that this setting should be used. It was subsequently found that by reverting to the .006" and .008" setting slow running was considerably improved, and it was concluded that with the smaller clearance the valves were not seating well. The state of the exhaust valve faces removed after 9000 miles running would point to this being so. On reverting to the wider clearances the general tappet noise seemed less than when previously complained of, attributed to the various working parts bedding down. There were, however, one or two noisy tappets and a noisy valve which could be heard on acceleration up to 20 m.p.h. The present position is, tappets Nos. A.7. and B.3. audible alongside engine but not in car. Valve B.10 comes up noisy at times, being audible in car. 2. CHANGE OF CLEARANCE. The longest period over which changes of clearance could be noted without the rocker shafts being removed for various reasons such as removal of cylinder heads, was 8000 miles. During this mileage the changes recorded were as follows, only changes in excess of .002" being given:- I.3.A. - 12 ) S/SLV. I.5.A. + 6 ) Inlets and E.7.A. - 6 ) exhausts. E.11.A. - 5 ) E.12.A. - 3 ) E.3.B. +3 ) KE.965 Exhausts. I.5.B. -4 ) E.6.B. +3 ) E.7.B. +3 ) S/SLV. inlets. E.11.B. +4 ) These figures are aggregates of adjustments carried out every 1000 miles. The majority of the inlet valves required no adjustment during this period. Rm{William Robotham - Chief Engineer}/IMW.{Ivan M. Waller - Head of Chateauroux} | ||