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).
Valve & fitting performance and low inertia spring drive modifications.
| Identifier | ExFiles\Box 5a\3\ 03-page171 | |
| Date | 14th December 1931 guessed | |
| -5- has settled down with no further distortion taken place. The valve guides E.57225 for the inlet valves had not the annulas turned in the top to prevent capillary attraction of the oil taking place (which is standard). VALVES & FITTINGS to LOP.E.55577. E.57301 Exhaust Valves S/SLV. new design. E.56821 Valve stem packings. Es.431 Stronger Valve Springs. The exhaust valves fitted were of a new design, with a view to overcoming the loss of clearance by lessening the heat of the valve head. The seating of the valves had distorted but there was no indication of the valve head having become loose in diameter or the neck of the valve having stretched that was the case with the present standard valve. The valves had apparently remained in one position as the portion of the seating opposite the valve ports were burnt and pitted whilst the remaining portion of the seating was good. The exhaust valves were sticking in the guides through carbon deposit on the upper portion of the valve stems, due to over-lubrication of the valve stems. The inlet valves were very wet with oil when examined due to the over-lubrication on the valve stems. The seatings were in a very fair condition and needed no attention. The valve stem packings had become fully compressed. The bottom valve spring cup was resting on the top of the valve guides thereby placing no load on the packings. This condition allows too much oil to be drawn down the inlet and exhaust valve guides. The fitting of the stronger valve springs is apparently the cause. The valve springs have been quiet and no valve springs have failed. The bottom valve spring cups show depressions where the valve springs dug into them. LOW INERTIA SPRING DRIVE to LOP. E.34745. Stronger damping springs fitted E.56208 free length increased from .680 to .880 Oil drain holes added in front and rear damper wheels. Driving Spring load 12 lbs at 17.5" rad. Damping friction load 14 lbs at 17.5" rad. To obtain friction load 6 damping springs E.56208 were removed. The added drain holes have proved beneficial as there was no sign of oil sludge inside the damper when dismantled and taken apart. The above loads had remained consistent. With the above loads we experienced engine gear rattles between the speeds of 15 - 16 M.P.H. when under load and with engine running lightly. The driving springs were taken out and stronger springs E.56200 were fitted, making the driving spring load 17 lbs at 17.5" rad. The damping friction load was 16 lbs at 17.5" rad. | ||