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).
Modified combustion chamber design (PL.525) for 3 1/4 bore engines.
| Identifier | ExFiles\Box 124\2\ scan0307 | |
| Date | 28th March 1941 | |
| To Rm.{William Robotham - Chief Engineer} from Jnr.{Charles L. Jenner} c. to Rm{William Robotham - Chief Engineer}/HH. Handwritten: B60 & B80 cast iron FB engine Handwritten: 1044 Jnr.{Charles L. Jenner}3/SW.28.3.41. Alum B.80 - 3 1/4 bore. Refer - Rm.{William Robotham - Chief Engineer}7/ML.18.3.41. Herewith design PL.525, showing the original shape of combustion chamber modified to suit 3 1/4 bore engines. In order to get a good area of throat (which we know is critical), the proportions of the chamber have been made smaller around the inlet valve and at the far side of the exhaust valve, this avoids a shallow head. The area of a 3 1/2 bore head is 10.36, but this one is 9.66 sq.ins. We show pistons flush with the top of cylinder bores, the bolting position of valves and sparking plugs are unaltered. A compression ratio of 6.75 : 1, is suitable for this size engine. Jnr.{Charles L. Jenner} [Signature] Original to Rm{William Robotham - Chief Engineer}/HH. Prints to Jnr.{Charles L. Jenner} and Ashby. | ||