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).
Testing and standardisation of a new high compression head for the Bentley.
| Identifier | ExFiles\Box 86\1\ scan0130 | |
| Date | 21th February 1935 | |
| To E.{Mr Elliott - Chief Engineer} from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. to By.{R.W. Bailey - Chief Engineer} +219 Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}6/KW. 21.2.35. Standardisation of High Compression Head for the Bentley. ------------------------ We have now completed our tests on the cylinder head to EB.2050. We are circulating a separate report which shows that this head weighs 4 1/4 lbs. less than the head which ran 10,000 miles on Hancock's car, gives about 5 more H.P. at top speeds for no increase of detonation, and has completed 20 hours' endurance running. The endurance running is similar to that which we use for pistons and under these conditions the standard split skirt Bentley piston cracks after about 17 hours' running. You will remember that on our 9 1/4 to 1 head we had a crack between the valves which we subsequently found was due to poor coring. We recommend that provision should be made for inspecting the water passages on the sparking plug side of the head. We also suggest that the drawing should be altered to ensure that on the exhaust side of the head the water gets close to the bar separating the two valves. If this is done, in view of our endurance running we think that we ought to standardise head EB.2050; for the 7 to 1 ratio to be offered to customers who require increased performance. We shall of course continue to run this head on the road, and produce others with which we shall have experience before these heads reach the customer. We have of course full experience of the large inlet valve on the 10,000 miles test. We should be glad if you will sign the Standardisation Sheet No. 254, so that we can get this completed and get EB.2050 into production. We have to accept that this head requires new rockers that are different to existing standard, but if it continues to give satisfaction we can with advantage make it the standard 6.5 compression ratio for production. Incidentally it will of course be run 10,000 miles on 5-B-IV. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||