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).
Valve guide failures and rattling issues on a Phantom model.
| Identifier | ExFiles\Box 17\6\ Scan118 | |
| Date | 14th October 1932 | |
| B. from Hs{Lord Ernest Hives - Chair}/GWH.{George W. Hancock - Head Chateauroux} C. By C. Hs{Lord Ernest Hives - Chair}/Hn.{F. C. Honeyman - Retail orders} X7060. Hs{Lord Ernest Hives - Chair}/GWH.{George W. Hancock - Head Chateauroux}1/KT.14.10.32. EXPL. WORK CARRIED OUT ON VALVES ETC. PHANTOM. X7230. (1) The exhaust guides first fitted for the new type Exhaust Valves failed because the guide extended too far beyond the cylinder boss. The extended portion collapsed causing a seizure of the Valves. The exposed portion of the guides also became mushroom in shape and crumbled away. (2) The new guides fitted to overcome this trouble were .275" shorter in length and strengthened up by making the taper 1 in 48 instead of 1 in 20. These guides were designed for the double valve springs which made the grummet much smaller in area of contact with the valve stem which we have found valuable for damping effect. (3) We found upon testing the car after fitting the above guides that excessive rattles developed from the exhaust valves at 59 m.p.h. in third gear and continued to rattle up to 70 m.p.h. The reason of this was found to be due to excessive clearance, .004" of the valve stems in the guides. This had come about by fitting the valves which had been cleaned up. The new guides having the maximum bore. (4) With the guides fitted having normal clearance - i.e. maximum .003", there was still a slight rattle at 59 m.p.h. which proved that damping of the valve is lost by decreasing the length of the guide. The amount of rattle from the valves under this condition was passable, also the duration is very small - i.e. 59-60 m.p.h. (5) When the valves were tested with the long guides using single valve springs, there was no appreciable swish or rattle from the valve springs or valves, the chief reason being, the damping effect on the valve stem caused by the tightening up of the exposed bottom portion of the guide. (6) From these results it seems wrong to have the long taper clearance at the bottom of the guide to prevent valves sticking on the Phantom (25 HP. does not have it). Hs{Lord Ernest Hives - Chair}/GWH.{George W. Hancock - Head Chateauroux} | ||