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).
History and development of an improved Phantom III cylinder head.
| Identifier | ExFiles\Box 93\4\ scan0080 | |
| Date | 6th November 1936 | |
| Sg.{Arthur F. Sidgreaves - MD} from Rm.{William Robotham - Chief Engineer} Hs.{Lord Ernest Hives - Chair} c. to E.{Mr Elliott - Chief Engineer} By.{R.W. Bailey - Chief Engineer} H2RT 1229 319 Rm{William Robotham - Chief Engineer}3/R.6.11.36. IMPROVEMENT IN P.III CYLINDER HEAD. The history of this improved cylinder head is as follows:- When we had the four carburetter scheme on P.III, it was developed as a replica of the Bentley, and, in consequence, a 6 port head was utilised. When we came to the duplex down-draught Stromberg carburetter, it was obvious from our results on the 25/30 that the 6 port head was not the best arrangement. As a temporary expedient, the P.III Cylinder head went into production with an arrangement whereby it was converted to 4 ports. At the same time, design put in hand a proper scheme for doing the job thoroughly, and this is a test on the final design. We think that the improvement is sufficiently great to justify fitting these cylinder heads to 35-EX before it goes to France; at the same time, we believe for the standard P.III these cylinder heads would be better with a short duration camshaft which would further improve the idling and low speed pick-up of the car at the expense of some of the increase on top horse-power. We think it is a mistake to give away anything with regard to the low speed performance on the standard P.III for a small gain in maximum speed, particularly in view of the fact that a Continental chassis is being evolved to cater for the high performance clientele. The limited road experience we have so far had indicates that the test bed figures are substantiated on the road. The main difficulty is that any increase in high speed performance aggravates our big end bearing trouble which is already unpleasantly acute. 35-EX will have, of course, what we hope will be improved big end bearings before it starts Continental tests. Our feeling at the moment is that it is much more important to improve the smoothness and docility of the standard P.III than augment its performance. Rm.{William Robotham - Chief Engineer} | ||