Modifications to the exhaust manifold for the Wraith III and Bentley III models.
| Identifier | ExFiles\Box 8\8\ 08-page35 | |
| Date | 18th March 1938 | |
| 623. EX/NO. c. Rm. {William Robotham - Chief Engineer} DA. {Bernard Day - Chassis Design} 8/G.18.3.38. WRAITH III & BENTLEY III. EXHAUST MANIFOLD.. Herewith please receive E.CD.542 Modified Exhaust Manifold - Wraith III. This modification has been made because of the failure of the existing manifold on the Wraith III car in France. The only difference in design between the existing Wraith III manifold and the production Bentley II. pipe is a slight offset of the downtake towards the rear instead of the downtake being central. It is possible that owing to the high average engine speed and the rather heavy petrol consumption that the pipe is running at a much higher temperature than on our standard engines with the resultant increase in expansion, also the increased flexibility of the engine mounting may be putting a strain on the manifold fixing due to the pull on the downtake pipe. We have therefore modified the flange fixing for the two end branches as follows :- (1). Increased expansion and contraction allowance of studs in slots from .087 to .125. (2). Flanges stiffened by making thicker. (3). Length of studs and stud bosses reduced by .125 to reduce bending on studs and improve the sliding of the flanges under the nuts. (4). Countersinks produced in end bores to assist in matching up with cylinder ports when pipe is distorted. Will you please detail and instruct these modifications experimentally. There are no changes required to the cylinder head for this experiment. DA. {Bernard Day - Chassis Design} | ||
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).