Poor finish of replacement cylinder bores for 3 1/2-litre Bentley engines, its impact on oil consumption and other issues.
| Identifier | ExFiles\Box 103\2\ scan0142 | |
| Date | 10th November 1936 | |
| K {Mr Kilner} /W. KC to Hs. {Lord Ernest Hives - Chair} K {Mr Kilner} /KC/DPB/10.11.36. The standard finish of Cylinder Bores. Replacement Cylinders 3 1/2-litre Bentley. -------------------- In accordance with your Hs {Lord Ernest Hives - Chair} 13/KW.2.11.36. I am of the opinion that the finish of the cylinder bores of the replacement cylinders sent to K from W for use where reground cylinders are necessary is not up to the standard of the remainder of the chassis. It has occurred to me that this finish possibly may have some bearing on the cases of spasmodic bad oil consumptions that occur in cars under a mileage of 5,000. Several cases of badly honed blocks have been brought to the notice of GWH {George W. Hancock - Head Chateauroux} and I understand that he has taken the matter up with Works. In my opinion, they compare unfavourably both from an accuracy and finish point of view with the reground cylinder blocks that are used day by day on the old type Bentleys. I have a case in point at the moment - the bores of the cylinder block No Y.4.BH are roughly finished in my opinion. The milling can be rubbed from a silver coin with all the ease in the world. Surely ( and I think you will agree with me here) this is not fair to an engine using an aluminium alloy piston and on the other hand, it does not give the modern lapped ring a chance to do its job accurately from the onset, also the accuracy of the machining leaves much to be desired. We had a case a few weeks ago, (22.9.36) Chassis No. B.7.FC which I believe was taken up by GWH {George W. Hancock - Head Chateauroux} with the Works. This 3 1/2-litre came in for R.20. No complaint of heavy oil consumption, but on examining the cylinder bores for wear, they had worn badly. The cylinder block was changed for a block of the first oversize and a new set of pistons and rings were fitted. On test an oil consumption of 400 m.p.g. was obtained. The block was dismantled and examined by both GWH {George W. Hancock - Head Chateauroux} and myself. -contd- | ||
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).