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).
Comparison table of constructional details for Rudge, Standard Bentley, and HP single/twin inlet engines.
| Identifier | ExFiles\Box 133\1\ scan0121 | |
| Date | 17th September 1936 | |
| CONSTRUCTIONAL DETAILS. | | Rudge | Standard Bentley | H.P. Single Inlet | H.P. Twin Inlet | |---|---|---|---|---| | Bore | 3.346" | 3.250" | 3.250" | 3.250" | | Stroke | 3.464 | 4.500 | 4.500 | 4.500 | | Compression Ratio | 7.3 | 6.4 | 6.5 | 6.5 | | Swept Volume | 499 cc. | 612 cc. | 612 cc. | 612 cc. | | Inlet Valve dia. | 1.200 | 1.400 | 1.750 | 1.225 | | Exhaust Valve dia. | 1.100 | 1.300 | 1.500 | 1.500 | | No. of Valves | 4 | 2 | 2 | 3 | | Total Inlet area | 2.160 | 1.450 | 2.295 | 2.220 in.² | | Total Exhaust area | 1.750 | 1.160 | 1.655 | 1.655 in.² | | Ratio Piston Area/Inlet area | 4.07 | 5.73 | 3.62 | 3.74 | | Ratio Piston Area/Exh.area | 5.03 | 7.16 | 5.02 | 5.02 | | Plug position | Centre | Side | Over Throat | Over Throat | | Max. B.M.E.P. | 164 | 124 | 137 | 137 lbs/in² | | Max. I.M.E.P. | 188 | 158 | 171 | 171 " " | | R.P.M. for max. torque | 4500 | 2600 | 3100 | 3100 | | R.P.M. for max. power | 5800 | 3500 | 4200 | 4200 | | Piston speed for max.torque | 2600 | 1950 | 2312 | 2312 ft/min | | Piston speed for max.power | 3350 | 2625 | 3150 | 3150 " " | | Inlet gas velocity (max. torque) | 176 | 183 | 141 | 145 ft/s. | | Inlet gas velocity (max.power) | 227 | 251 | 190 | 196 " " | | Exhaust gas velocity (max. torque) | 218 | 232 | 194 | 194 " " | | Exh. gas velocity (max.power) | 281 | 314 | 264 | 264 " " | | Valve lifts Inlet/Exhaust | .310/.310 | .400/.400 | .400/.400 | .325/.400 | | ||