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).
Table showing engine boiling temperatures in Celsius based on different types of bonnet ventilation at various speeds.
| Identifier | Morton\M19\ img174 | |
| Date | 16th May 1931 guessed | |
| figures given are temp. at which Car will boil if driven for sufficiently long under the conditions named. C° | Type of Bonnet Ventilation | All out | 45 M.P.H. | 30 M.P.H. | |-------------------------------------|---------|-----------|-----------| | Vertical Louvres. | 44.5 | 37.5 | 36.5 | | Three ventilating shutters per side.| 41.5 | 33.0 | 32.5 | | No bonnet ventilation. | 38.0 | - | 27.5 | Tests on 19-EX. Rad. used. small Hexagon 11.S.A. Hexagon .305 across flat. Centre .225 diam. round. 18 dents. Car weight. 48 cwt. Radiator dimensions 25 x 35". Radiator shutters fitted for all tests. Axle 11 X 41 Louvred Bonnet F.7929/ Shutter Bonnet N.sch.3232 | ||