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).
General comments regarding lash adjuster parts, lubrication, and cam contour design.
| Identifier | ExFiles\Box 125\1\ scan0124 | |
| Date | 21th November 1934 guessed | |
| -4- General Comments. In addition to the information given above relative to lash adjuster parts, the following points are equally important : 1. The lubricating oil in the valve gear must be clean. In the Cadillac installation, all oil to the valve gear must pass thru an edge type filter immediately preceding its delivery to Rocker Shafts. Oil pressure at the rocker shafts is reduced to 2#/in.2 - 5#/in.2 by means of a restricting orifice in the oil feed line. This orifice will plug with dirt unless placed between the oil filter and the rocker shaft, which position requires a filter case of sufficient strength to withstand the excessive pressures encountered when starting a cold engine with high viscosity oil in the crankcase. Any aeration of the oil in the valve gear causes erratic action of the lash adjusters. 2. Lubrication of the valve stem end of the rocker arms is no different than with any other valve in head engine, except that lubrication is apt to be excessive due to the amount of oil needed for operation of the lash adjusters. As a consequence, particular care must be taken to shield the valve stems and guide bushings from excessive lubrication. 3. The design of the cam contour may require additional study due to the use of the adjusters. The valve lash at the instant of closing of the valve is a variable quantity, depending upon the deflections of the parts in the valve operating mechanism and the depression of the plunger in the cylinder. As a consequence of this depression of the plunger, the height of the lamp or easement on the cam must be determined experimentally with the hydraulic lash adjusters as designed for any particular engine. In other words, the maximum lash obtained when the plunger is depressed due to valve spring loading should not be in excess of the height of the cam ramp above the base circle. | ||