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).
Graph comparing various Bentley cylinder heads by air-flow tests.
| Identifier | ExFiles\Box 86\1\ scan0047 | |
| Date | 7th December 1933 guessed | |
| COMPARISON OF VARIOUS BENTLEY CYLINDER HEADS BY AIR-FLOW TESTS. FLOW. CU. FT/MIN PRESS. DIFF: ACROSS VALVE - INS. HG. (1.5" VALVE) (1.4" VALVE) (1.5" VALVE) (1.5" VALVE) (1.4" VALVE) EB.1237 ALUM. HEAD - STREAMLINED PORT INLET TURBULENCE REMOVED. STD. WOODEN MODEL. (CAST IRON) LARGE INLET BENTLEY HEAD EB615 EB1237 - STREAMLINED PORT ETC EB1237 - ALUM HEAD. STD CAST IRON HEAD - E.B. 615. ALL CURVES AT 0.400" LIFT | ||