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).
Technical discussion on exhaust valve timing, camshaft design, and valve lift, including a comparison with American cars.
| Identifier | ExFiles\Box 182\M19\ img202 | |
| Date | 17th June 1931 | |
| - 2 - (1) Dependant on Exhaust back pressure and on exhaust valve timing, i.e. increase exhaust valve tappet clearance roar increased, divide exhaust manifold into 2 (Silver Ghost) no roar. Therefore we may be able to get over the trouble though Hs.{Lord Ernest Hives - Chair} is not so optimistic as I am. In case we cannot, we ought to have a camshaft where the inlet opens at T.D.C. that we know will be all right for roar, and in any case might give a better low speed M.E.P. than the ultra long duration shaft, i.e. an improved standard shaft where the one you have given us might be considered a Sports Phantom shaft. Hs.{Lord Ernest Hives - Chair}381 shews what we can do with two existing P.II. camshaft exhaust cams. We should then increase the valve lift by .050 on the rocker leverage and get what we want. The advantage of increasing the valve lift - by the rocker instead of the cam is - (1) Only the valve gets the increased acceleration, i.e. tappet and push rod acceleration as before, and load on cam thereby less than with the high lift cam. (2) Sliding of rock across valve stem end reduced. From our Exp. point of view it enables us to get twice as many results with each camshaft, and rockers are easy to make. OTHER MAKES OF CAR VALVE LIFT ETC. We send you a sheet of 1931 American Cars. We do not think they are of much value as all the U.S.A. valve areas are so much larger than ours. For the moment we think a small valve with a high lift may be in many ways advantageous. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||