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).
Design options and modifications for Bentley High Compression Heads.
| Identifier | ExFiles\Box 86\1\ scan0133 | |
| Date | 23th February 1935 | |
| +Wq To Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} from E.{Mr Elliott - Chief Engineer} c. Sg.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} By.{R.W. Bailey - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Mths.{Reg Matthews} Bentley High Compression Heads. Referring to Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}11/KW.20.2.35 and Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}6/KW. 21.2.35, we have now thoroughly investigated the position with respect to the above and it appears to us as follows:- Designs are issued to LeC.4319 and 4348 for applying hydraulic tappets with 1.5 inlet and 1.3 exhaust valves and valve centres .062 closer than standard to Bentley, and with standard compression ratio actually 6.35 to 1. These are being detailed. We are asked to sign a standardisation sheet, No.X.254 for a non hydraulic higher compression head 7 to 1 with valve centres .134 closer than standard and with 1.5 inlet and 1.3 exhaust, to EB.2050 to be fitted only in cases where customers require improved performance. Alternatively we are asked to sign sheet X.219 for a head to LeC.3662 with standard valve centres 1.5 inlet and 1.2 exhaust with somewhat less performance as shown in Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}11/KW.20.2.35, but which is being re-tested with 1.3 exhaust valves similar to EB.2050. These heads are applicable to production prior to the introduction of hydraulic tappets. My view is that EB.2050 involves too many alterations in its application for the advantage over LeC.3662, which advantage may be washed out when you test the latter with 1.3 exhaust valves similar to EB.2050 as mentioned in Hs{Lord Ernest Hives - Chair}/Mths.{Reg Matthews}12/KW.20.2.35. EB.2050 requires new rocker stampings and rocker valve gear generally, new push rods, and washers to make up the .075 difference in cylinder stud length, new gaskets, and modification to oil supply pipe to rockers. | ||