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).
Summary of test results comparing different camshafts and the effects of various valve springs on engine performance.
| Identifier | ExFiles\Box 17\6\ Scan240 | |
| Date | 15th June 1934 | |
| -2- Summarising the above results indicates that the inlet cam of E.82448 and the exhaust cam of E.80070 are better than the inlet cam of E.80070 and the exhaust cam of E.82448 respectively. Also, using similar springs on the exhaust as inlet valves the camshaft E.80070 is 150 R.P.M. better off than the camshaft E.82448. Individual cams and the speed at which they start to give trouble varies considerably and it could not be guaranteed that two camshafts of the same piece number would give identical results. An example of this is that during one test the following figures were obtained :- No. 6 cylinder exhaust cam at 2800 R.P.M. Nos. 1 & 6 " " " 2900-3000 R.P.M. Nos. 1,3,4 & 6 " " " 3100 R.P.M. Comparing the opening and closing contours of the cam No. 5 as being good, and No. 6 as bad, shown on Hs.{Lord Ernest Hives - Chair}1438, there is little difference in the curve to indicate such a wide range of speed. At .013 valve lift where the main acceleration commences, the slope of the opening curve of No. 5 is slightly more gradual than that of No. 6. The closing curves have more disparity and at .020 valve lift No. 6 shows a greater rate of closing than No. 5. We have interchanged bottom tappets, valve springs and push rods without affecting the speeds at which the various valves give trouble. Effect of Valve Springs. Numerous varieties of springs have been tried ranging from seat loadings of 50 lbs. to 110 lbs. and ratings from 110 lbs/inch to 260 lbs/inch. The following example illustrates the effect of the seat loading and rating. | ||