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).
Test results and specifications for a Packard 12-cylinder engine.
| Identifier | ExFiles\Box 37\1\ scan 217 | |
| Date | 25th June 1920 | |
| X3949 To R.{Sir Henry Royce} from Hs.{Lord Ernest Hives - Chair} c. to CJ. c. to Bn.{W.O. Bentley / Mr Barrington} c. to E.{Mr Elliott - Chief Engineer} c. to Da.{Bernard Day - Chassis Design} Hs{Lord Ernest Hives - Chair}7/LG25.6.20. X.435. RE PACKARD 12-CYLINDER ENGINE. X3949 We have been running the Packard 12-cylinder engine on the Test Bed. We found it was quite convenient to remove the engine and gearbox complete and fix it on the Bed. The size of the Packard engine is 3" bore - 5" stroke. The swept volume of the engine is 424.1 cu. ins. which means that it is 6.8% smaller than our present 40/50 chassis. The HP of the Packard engine on the Bench is as follows:- Eng. revs. | HP. | Pts. per HP. hour. | Comp. lbs. | Vacuum in Ind. Pipe. | Remarks. 500 | 21.2 | .85 | 95 | | 750 | 31.8 | .78 | 95 | | Comp: ratio 5 to 1 1000 | 41.6 | .74 | 93 | .75" | Lift on inlet valve .310" 1250 | 52.0 | .77 | T | 1.1" | " " exhaust " .305" 1500 | 57.5 | .79 | 92 | 1.6" | 1750 | 68.0 | .76 | --- | 2.05" | Power curve taken. 2000 | 71.6 | .76 | 86 | 2.6 | with free exhaust. 2250 | 75.0 | .76 | --- | | 2500 | 85.0 | .78 | 75 | | contd. | ||