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).
Tests to improve slow running by adjusting camshaft overlap, tappet clearance and induction systems.
| Identifier | ExFiles\Box 124\3\ scan0260 | |
| Date | 4th December 1934 | |
| -4- Camshaft. From the tests so far it is evident that camshaft overlap is playing the major part in destroying slow running. Tests were carried out to determine the minimum tappet clearance at which desired slow running could be obtained, with the best induction system arrangement found so far in these tests. At .015 tappet clearance, slow running is good (10° overlap - crank angle), but a further improvement can be obtained by running with .020 tappet clearance (4° overlap) and this we would term the desired slow running. Assuming that the two factors which upset slow running are as follows - (1) Camshaft overlap (2) Wet vapour upsetting distribution working at .006 tappet clearance, No. 1 is predominant, so that the presence of (2) is not then fully realized. At .015 tappet clearance (2) is predominant, as (1) has been reduced to within the limit of reasonable slow running. We can now therefore obtain a value for the three induction pipes tested and mentioned in this report. The preceding tests were repeated with tappet clearance of .015”. Induction pipes in order of merit - 1st. Lowered pipe EX.16451. 2nd. Totally heated 1.375 bore pipe, but otherwise standard. 3rd. Standard Bentley pipe. | ||