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 specifications for 12-cylinder engines from various car manufacturers.
| Identifier | ExFiles\Box 43\4\ Scan336 | |
| Date | 1st February 1932 | |
| 12 CYLINDER ENGINES. Car. Capacity. Vee° Balance Wts. Damper. Journal Dia. No: of Bearing Packard. 6150 67° Yes Yes 2.750 4 Auburn. 6420 45° Yes Yes 3.000 4 Lincoln. 7350 65° YES Yes 2.500 7 Pierce Arrow 7050 80° YES Yes 2.400 7 Cadillac 6030 45° YES YES Voisin 4385 60° 4.000 3 Hispano 9100 60° Tatra 6000 65° 3.000 Maybach 6970 60° Yes Yes 2.850 8 Horch 6100 7 Daimler. 6511 60° Yes 7 Proposed R.R. 6250 | ||