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).
Results of a rough test on masked inlet valves.
| Identifier | Morton\M19\ img270 | |
| Date | 29th October 1931 | |
| To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson} c. to Sg.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} c. to L. Da.{Bernard Day - Chassis Design} c. to HY.{Tom Haldenby - Plant Engineer} ORIGINAL Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson}1/KT.29.10.31. X7090. MASKED INLET VALVES. With reference to your suggestion that it would be worth trying slightly masked inlet valves, we have carried out a rough test the results of which are attached. The cam. forms we used were :- Inlet. R.{Sir Henry Royce} engine Cam Form to Sch.1069 Exhaust. Standard Exhaust Cam Form. These were made up into two shafts having 108° & 112° between the cams respectively. The inlet valves were masked to a depth of .050" and this loss of lift was then compensated for by fitting the high lift rockers which gave an absolute lift of .470 on the exhaust valve and .547" on the inlet valve. The masks were made a dia. .008 greater than that of the valve and gave no trouble during the tests. We put a slight taper on the vertical portion of the mask head to guide it into the mask in case the clearance had proved too small. The results shew that with the 112° shaft we can gain a max. of 6 B.H.P. for the same low speed M.E.P. or alternatively with the 108° shaft we can gain a max. of 5 B.H.P. at the top and also 5 B.M.E.P. at the bottom which seems a better all round result. The curves for the 114° W.W. shaft are with high lift rockers so that this shaft is not penalised by having less lift than the masked valves. We put an exhaust system on the engine and could hear no unusual noise from the masked valves. There was plenty of induction pipe roar but the quantitative value of this is not easy to judge except on the road. The slow running appeared to be O.K. We are inclined to think that we should have done better with slightly less mask which would have given | ||