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 report on an improved 25 HP car at Brooklands with modification details and performance notes.
| Identifier | ExFiles\Box 29\3\ Scan342 | |
| Date | 29th August 1931 | |
| To R.{Sir Henry Royce} From Hs.{Lord Ernest Hives - Chair} c. to Sg.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} c. to E.{Mr Elliott - Chief Engineer} Da.{Bernard Day - Chassis Design} c. to By.{R.W. Bailey - Chief Engineer} Hs.{Lord Ernest Hives - Chair}2/MJ.29.8.31. x788 x2770 TESTS ON BROOKLANDS. IMPROVED 25 HP. CAR. Tests were carried out on Brooklands on Wednesday the 26th.inst. with 12-04. car. This car has a standard 'China' engine with the following modifications :- (1) Compression Ratio 5.65 instead of the present standard 5.0. (2) Camshaft 112° angle between the cams instead of 110°. (3) Modified rockers in order to increase the valve lift from .344 to .394. (4) Exhaust system - Standard short type F.2 silencer was fitted. (5) Axle ratio 12/50 instead of standard 11/50. (6) Valve springs increased strength to enable engine to run up to 4000 R.P.M. without balancing. Prints attached give the performance on the track. We put more reliance on to the lap figures than on to the half mile because the half mile is influenced so much by the direction of wind. 12-04. car on the road is very impressive. With the standard R.A. carburetter on the main arterial roads, with favourable conditions as regards either gradient or wind, the car will get to an actual 77 or 78 m.p.h. With the S.U. carburetter we have had it over 80. It will be appreciated by this that the car is entirely different to the present cars we are selling. We are certain that with cars of this type we could interest people in the 25 HP. who at the present time are not interested because the car does not give them a thrill. Hs.{Lord Ernest Hives - Chair} | ||