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).
Power comparison graph for the Phantom III engine, comparing 4-port and 6-port cylinder heads.
| Identifier | ExFiles\Box 93\4\ scan0084 | |
| Date | 7th October 1936 | |
| SP{Mr Spinney} 38 PHANTOM III POWER COMPARISON COMPARISON BETWEEN 4 PORT AND 6 PORT HEADS BOTH HEADS WITH SAME WATER HEAT HOT SPOT (STD) CURVES WITH STD STROMBERG CARBURRETER (OPEN EXHAUST) STANDARD 6 PORT HEAD VALVES. INLET 1.450 DIA. EXHAUST 1.25 DIA. 4 PORT HEAD VALVES. INLET 1.500 DIA. EXHAUST 1.300 DIA. CURVE ① ---o---o--- 4 PORT HEAD CURVE ② ----o----o---- STD HEAD TIMING WITH .020 CL'CE EC 8° TOC IO 42° EO 47° 107° B.H.P MEP INS Hg DEPN IND DEPN R.P.M. MEP (lbs/□") Platts 7-10-36 | ||